TABLE OF CONTENTS.

The Orion Nebula,[Frontispiece]
The Crossley Reflector of the Lick Observatory, Page[11]
List of Nebulæ and Clusters Photographed, "[30]
Catalogue of New Nebulæ Discovered on the Negatives, "[31]
Positions of Known Nebulæ Determined from the Crossley Negatives, "[42]
List of Illustrations, "[45]
Illustrations,following"[46]

THE CROSSLEY REFLECTOR OF THE LICK OBSERVATORY.[1]

By James E. Keeler.

The Crossley reflector, at present the largest instrument of its class in America, was made in 1879 by Dr. A. A. Common, of London, in order to carry out, and test by practical observation, certain ideas of his respecting the design of large reflecting telescopes. For the construction of the instrument embodying these ideas, and for some fine astronomical photographs obtained with it, Dr. Common was awarded the gold medal of the Royal Astronomical Society in 1884.

In 1885, Dr. Common, wishing to make a larger telescope on a somewhat similar plan, sold the instrument to Edward Crossley, Esq., F. R. A. S., of Halifax, England. Mr. Crossley provided the telescope with a dome of the usual form, in place of the sliding roof used by its former owner, and made observations with it for some years; but the climate of Halifax not being suitable for the best use of such a telescope, he consented, at the request of Dr. Holden, then Director of the Lick Observatory, to present it to this institution. The funds for transporting the telescope and dome to California, and setting them up on Mount Hamilton, were subscribed by friends of the Lick Observatory, for the most part citizens of California. The work was completed, and the telescope housed in a suitable observatory building, in 1895.[2]

On taking charge of the Lick Observatory in 1898, I decided to devote my own observing time to the Crossley reflector, although the whole of my previous experience had been with refracting telescopes. I was more particularly desirous of testing the reflector with my own hands, because such preliminary trials of it as had been made had given rise to somewhat conflicting opinions as to its merits.[3] The result of my experience is given in the following article, which is written chiefly with reference to American readers. If I have taken occasion to point out what I regard as defects in the design or construction of the instrument, I have done so, not from any desire to look a gift horse in the mouth, but in the interest of future improvement, and to make intelligible the circumstances under which the work of the reflector is now being done and will be done hereafter. The most important improvements which have suggested themselves have indeed already been made by Dr. Common himself, in constructing his five-foot telescope. The three-foot reflector is, in spite of numerous idiosyncracies which make its management very different from the comparatively simple manipulation of a refractor, by far the most effective instrument in the Observatory for certain classes of astronomical work. Certainly no one has more reason than I to appreciate the great value of Mr. Crossley’s generous gift.

DOME OF THE CROSSLEY REFLECTOR.

The Crossley dome is about 350 yards from the main Observatory, at the end of a long rocky spur which extends from the Observatory summit toward the south, and on which are two of the houses occupied by members of the Observatory staff. It is below the level of the lowest reservoir, “Huyghens,” which receives the discharge from the hydraulic machinery of the 36-inch refractor, and therefore the water engine furnished by Mr. Crossley for turning the dome can not be used, unless a new water system—overflow reservoir, pump and windmill—is provided. In this respect a better site would have been a point on the south slope of “Kepler,”—the middle peak of Mount Hamilton—just above the Huyghens reservoir. No addition to the present water system would then have been needed. The slope of the mountain at this place might cut off the view of the north horizon, but since the telescope can not be turned below the pole, this would be a matter of no consequence. Water-power for the dome is not, however, really necessary.

The cylindrical walls of the dome, 36¼ feet inside diameter, are double, and provided with ventilators. Opening into the dome, on the left of the entrance, are three small rooms, one of which has been fitted up as a photographic dark room, and another, containing a sidereal clock and a telephone, which communicates with the main Observatory, as a study, while the third is used for tools and storage. There is also a small room for the water engine, in case it should be used. The dome is at present supplied with water from only the middle reservoir, Kepler, which is reserved for domestic purposes and is not allowed to pass through the machinery.

The dome itself, 38 feet 9 inches in diameter, is made of sheet-iron plates riveted to iron girders. It also carries the wooden gallery, ladders, and observing platform, which are suspended from it by iron rods. The apparatus for turning the dome consists of a cast-iron circular rack bolted to the lower side of the sole-plate, and a set of gears terminating in a sprocket-wheel, from which hangs an endless rope. As the dome does not turn easily, it has been necessary to multiply the gearing of the mechanism so that one arm’s-length pull on the rope moves the dome only about one inch. In some positions of the telescope the dome can not be moved more than six or eight inches at a time without danger of striking the tube, and this slowness of motion is then not disadvantageous. It is only when the dome has to be moved through a considerable angle, as in turning to a fresh object, or in photographing some object which passes nearly through the zenith, that the need for a mechanical means of rotation is felt.

The observing slit, 6 feet wide, extends considerably beyond the zenith. It is closed by a double shutter, which is operated by an endless rope. The upper part, within the dome, is also closed by a hood, or shield, which serves to protect the telescope from any water that may find its way through the shutter, and which is rolled back to the north when observations are made near the zenith. I have recently fitted the lower half of the slit with a wind-screen, which has proved to be a most useful addition. It is made of tarpaulin, attached to slats which slide between the two main girders, and is raised or lowered by halliards, which belay to cleats on the north rail of the gallery. A more detailed description of the dome has been given in an article by Mr. Crossley,[4] from which the reduced figure in Fig. 1[5] has been taken.

The mounting of the three-foot reflector has been very completely described and illustrated by Dr. Common,[6] so that only a very general description need be given here. The most important feature of the mounting is that the telescope tube, instead of being on one side of the polar axis, as in the usual construction, is central, so that the axis of the mirror and the polar axis are in the same line when the telescope is directed to the pole. The declination axis is short, and is supported by a massive goose-neck bolted to the upper end of the polar axis. The mirror is placed just above the declination axis. Its weight, and the weight of the whole tube and eye-end, are counterpoised by slabs of lead, placed in two iron boxes, between which the goose-neck of the polar axis passes. The great advantage of this arrangement, and the controlling principle of the design, is that the telescope is perfectly free to pass the meridian at all zenith distances. No reversal of the instrument is needed, or is indeed possible.

THE CROSSLEY REFLECTOR.

For long-exposure photography, the advantage above referred to is obvious, but it is attended by certain disadvantages. One of these is that a very much larger dome is required than for the usual form of mounting. Another is the great amount of dead weight which the axes must carry; for the mirror, instead of helping to counterpoise the upper end of the tube, must itself be counterpoised. When anything is attached to the eye-end (and in astrophysical work one is always attaching things to the eye-end of a telescope), from ten to twenty times as much weight must be placed in the counterpoise boxes below the declination axis. Where room is to be found for the weights required to counterpoise the Bruce spectrograph, is a problem which I have not yet succeeded in solving.

In his five-foot reflector, Dr. Common has caused the telescope tube to swing between two large ears, which project from the upper end of the boiler-like polar axis, the pivots constituting the declination axis being near, but above, the lower end of the tube. The mirror, therefore, helps to counterpoise the upper end of the tube. This I regard as a distinct improvement. The danger of large masses of metal near the mirror injuring the definition is, in my opinion, imaginary; at least there is no such danger on Mount Hamilton, where the temperature variations are unusually small. Experience with the Crossley reflector, as well as with the other instruments of the Lick Observatory, shows that the definition depends almost entirely on external conditions.

My first trials of the reflector, as first mounted at the Lick Observatory, showed that the center of motion was inconveniently high. Among other difficulties arising from this circumstance, the spectroscope projected beyond the top of the dome, so that it had to be removed before the shutter could be closed. In July, 1898, the pier was therefore cut down two feet. This brought the eye-end down nearly to the level of the gallery rail, where it was at a convenient height for the observer when sitting on a camp-stool, and it made all parts of the mounting more accessible. Toward the north and south, the range of the telescope, being limited in these directions by the construction of the mounting, was not affected by the change, but the telescope can not now be used at such low altitudes as formerly, near the east and west points of the horizon. The only occasion likely to call for the use of the reflector in these positions is the appearance of a large comet near the Sun, and, after some consideration, I decided to sacrifice these chances for the sake of increasing the general usefulness of the instrument. Except in rare cases, all observations are made within three hours of the meridian.

To adapt the mounting to the latitude of Mount Hamilton, a wedge-shaped casting, shown in the illustration, had been provided, but through some error, arising probably from the fact that the telescope had been used in two different latitudes in England, the angle of the casting was too great. When the pier was cut down its upper surface was therefore sloped toward the south, in order to compensate the error in the casting. Plate VII shows the instrument very nearly as it is at the present time.

The polar axis of the Crossley reflector is a long, hollow cylinder, separated by a space of about one-eighth of an inch from its concentric casing. The idea was to fill this space with mercury, and float the greater part of the thrust of the axis, the function of a small steel pin at the lower end being merely to steady the axis. But this mercury flotation, as applied to the Crossley telescope, is a delusion, as I think Mr. Crossley had already found. The mercury, it is true, relieves the thrust to some extent, but it greatly increases the already enormous side pressure on the steel pin at the bottom, thus creating a much greater evil than the one it is intended to remedy. The workmen who set up the mounting inform me that the small bearing at the lower end of the polar axis is badly worn, as I should expect it to be. Instead of putting mercury into the space intended for it, I have therefore poured in a pint or so of oil, to keep the lower bearing lubricated. For the reasons indicated above, the force required to move the telescope in right ascension is perhaps five times greater than it should be. The lower end of the polar axis ought to be fitted with ball bearings to take the thrust, and with a pair of friction wheels on top; but it would be difficult to make these changes now. It should be observed that the disadvantages of the mercury flotation are considerably greater at Mount Hamilton than at the latitude for which the telescope was designed.

THE CROSSLEY REFLECTOR.

As already stated above, the range of the telescope is limited on the south by the construction of the mounting. The greatest southern declination which can be observed is 25°. In England this would doubtless mark the limit set by atmospheric conditions, but at Mount Hamilton it would be easy to photograph objects 15° farther south, if the telescope could be pointed to them.

The original driving-clock having proved to be inefficient, at least without an electric control, a new and powerful driving-clock was made by the Observatory instrument maker, from designs by Professor Hussey. In its general plan it is like that of the 36-inch refractor. The winding apparatus, contained in the large casting of the original mounting, has no maintaining power, and can not easily be fitted with one. The clock could in no case be wound during a photographic exposure, on account of the tremors attending the operation, but it would be somewhat more convenient to have the stars remain on the plate during the winding. With a little practice, however, one can wind the clock without actually stopping it, though the object must afterwards be brought back to its place by means of the slow motion in right ascension.

Two finders have recently been fitted to the Crossley reflector. One has an object-glass of four inches aperture and eight feet six inches focal length, with a field of about 1° 2′, which is very nearly the photographic field of the main telescope. Its standards are bolted to one of the corner tubes of the reflector. The other finder has a three-inch objective and a large field. It had not been mounted when the photograph for the plate was made.

When a telescope is used for photographing objects near the pole, with long exposures, the polar axis must be quite accurately adjusted, for otherwise the centers of motion of the stars and of the telescope will not agree, and the star images will be distorted. It is true that with a double-slide plate-holder, like the one used with the Crossley reflector, one star—namely, the guiding star—is forced to remain in a fixed position with respect to the plate; but the differential motion of the other stars causes them to describe short arcs, or trails, around this star as a center. A considerable part of the spring of 1899 was spent in efforts to perfect the adjustment of the polar axis, an operation which, on account of the peculiar form of the mounting, offers unusual difficulties.

In the first plan which was tried, the reflector was used as a transit instrument. The inclination of the declination axis was determined with a hanging level which had been provided by Mr. Crossley, the hour circle and polar axis being very firmly clamped. The clock correction being known from the records kept at the Observatory, the collimation and azimuth constants were found by the usual formulæ. This method failed to give satisfactory results, and it was found later that the declination and polar axis were not exactly at right angles.

There is only one part of the sky on which the telescope can be reversed; namely, the pole. A method which promised well, and on which some time was spent, consists in photographing the pole (the declination axis being horizontal) by allowing the stars near it to trail for ten or fifteen minutes, then turning the polar axis 180° and photographing the pole again on the same plate. Half the distance between the images gives the error of the polar axis, which, if the plate is properly oriented, is easily resolved into horizontal and vertical components; while the distance of each image from the center of the plate is this error increased or diminished by twice the deviation of the telescope axis. In this case the vertical component depends upon the reading of the declination circle, and the horizontal component gives the error of collimation. This method failed, however, to give consistent results, mainly on account of instability of the mirror, and was abandoned.

The use of the large mirror for purposes of adjustment was finally given up, and the axis was adjusted by observations of Polaris with the long finder, in the usual manner. In order to reach the star at lower culmination the finder tube had to be thrown out of parallelism with the main telescope.

The base-plate having no definite center of rotation in azimuth, and the wedges and crowbars used for moving it being uncertain in their action, a watch telescope, provided with a micrometer eyepiece, was firmly secured to the mounting throughout these operations, in such manner that a mark on the southern horizon could be observed through one of the windows of the dome. The errors of the polar axis were finally reduced to within the limits of error of observation.

The movable hour circle and driving wheel of the Crossley reflector has two sets of graduations. The driving screw having been thrown out of gear, the circle is turned until the outer vernier indicates the sidereal time, whereupon the driving screw is thrown into gear again. The inner vernier is then set to the right ascension of the object which it is desired to observe. As an inconsistency, of minor importance, in the design of the mounting, I may note that the slow motion in right ascension changes the reading of the outer vernier instead of that of the inner one. In practice, however, no inconvenience is caused by this construction.

In the early experiments and photographic work with the Crossley telescope, irregularities in driving were a source of great annoyance. Dr. Roberts, in laying down the conditions which should be fulfilled by a good photographic telescope, says that a star should remain bisected by a thread in the eyepiece for two minutes at a time. The Crossley telescope was so far from fulfilling this condition that a star would not keep its place for two consecutive seconds; and the greatest alertness on the part of the observer did not suffice to ensure round star images on a photographic plate. It was obvious that the fault did not lie with the driving clock; in fact, many of the sudden jumps in right ascension, if explained in this way, would have required the clock to run backward; nevertheless the clock was tested by causing its revolutions to be recorded on a chronograph at the main Observatory, together with the beats of one of the standard clocks. For this purpose a break-circuit attachment was made by Mr. Palmer. The errors of the clock were in this way found to be quite small.

The principal source of the irregularities was found in the concealed upper differential wheel of the Grubb slow motion. This wheel turned with uncertain friction, sometimes rotating on its axis, and sometimes remaining at rest. After it was checked the driving was much better, and was still farther improved by repairing some defective parts of the train. Small irregularities still remain. They seem to be partly due to inaccuracies in the cutting of the gears, or of the teeth of the large driving wheel, and partly to the springing of the various parts, due to the very considerable friction of the polar axis in its bearings. The remaining irregularities are so small, however, that they are easily corrected by the screws of the sliding plate-holder, and with reasonable attention on the part of the observer, round star images are obtained with exposures of four hours’ duration.

The large mirror, the most important part of the telescope, has an aperture of three feet, and a focal length of 17 feet 6.1 inches. It was made by Mr. Calver. Its figure is excellent. On cutting off the cone of rays from a star, by a knife-edge at the focus, according to the method of Foucault, the illumination of the mirror is very uniform, while the star disks as seen in an ordinary eyepiece are small and almost perfectly round. They are not, I think, quite so good as the images seen with a large refractor; still, they are very good indeed, as the following observations of double stars, made recently for this purpose, will show.

Several close double stars were examined on the night of April 17, 1900, with a power of 620. The seeing was four on a scale of five. The magnitudes and distances of the components, as given in the table, are from recent observations by Professor Hussey with the 36-inch refractor.

Star. Mag. d. Result of Obs.
ΟΣ 208 (φ Urs. Maj.) 5.0, 5.5 0″.35 Not resolved; too bright.
ΟΣ 249, AB 7.2, 8.0 0 .54 Easily resolved.
ΟΣ 250 7.7, 8.0 0 .44 Resolved.
ΟΣ 267 8.0, 8.2 0 .30 Just resolved at best moments.

Although the theoretical limit of resolution for a three-foot aperture is not reached in these observations, I do not think the mirror can do any better.

The small mirror, or flat, at the upper end of the tube, is circular, the diameter being nine inches. Its projection on the plane of the photographic plate is therefore elliptical; but the projection of the mirror and its cell on the plane of the great mirror is very nearly circular.

The small mirror, acting as a central stop, has the effect of diminishing the size of the central disk of the diffraction pattern, at the expense of an increase in the brightness of the system of rings. To this effect may be due, in part, the inferiority of the reflector for resolving bright doubles, as compared with a refractor of the same aperture. For photographic purposes, it is evident that the mirror is practically perfect.

The upper end of the tube can be rotated, carrying with it the flat and the eye-end. Whenever the position is changed, the mirrors have to be re-collimated. In practice it is seldom necessary to touch the adjusting screws of the mirrors themselves. The adjustment is effected by means of clamping and butting screws on the eye-end, and a change of the line of collimation, with respect to the finders and the circles, is avoided. The operation is generally referred to, however, as an adjustment of the mirrors.

For adjusting the mirrors there are two collimators. One of these is of the form devised by Mr. Crossley.[7] It is very convenient in use, and is sufficiently accurate for the adjustment of the eye-end when the telescope is used for photographic purposes, inasmuch as the exact place where the axis of the large mirror cuts the photographic plate is not then a matter of great importance, so long as it is near the center. Moreover, as stated farther below, the direction of the axis changes during a long exposure. The other collimator is of a form originally due, I think, to Dr. Johnstone Stoney. It consists of a small telescope, which fits the draw-tube at the eye-end. In the focus of the eyepiece are, instead of cross-wires, two adjustable terminals, between which an electric spark can be passed, generated by a small induction machine, like a replenisher, held in the observer’s hand. The terminals are at such a distance inside the principal focus of the objective, that the light from the spark, after reflection from the flat, appears to proceed from the center of curvature of the large mirror. The rays are therefore reflected back normally, and form an image of the spark which, when the mirrors are in perfect adjustment, coincides with the spark itself. The precision of this method is very great. It is in fact out of proportion to the degree of refinement attained in other adjustments of the reflector, for a slight pressure of the hand on the draw-tube, or movement of the telescope to a different altitude, instantly destroys the perfection of the adjustment. I have provided these collimators with an adapter which fits the photographic apparatus, so that one can adjust the mirrors without having to remove this apparatus and substitute for it the ordinary eye-end carrying the eyepieces.

For visual observation the Crossley telescope is provided with seven eyepieces, with powers ranging from 620 downward. The lowest power is only 60, and consequently utilizes only 12 inches of the mirror, 9 of which are covered by the central flat. It is therefore of little value, except for finding purposes. The next lowest power utilizes 28 inches of the mirror. The other eyepieces call for no remark.

But, while the Crossley reflector would doubtless be serviceable for various kinds of visual observations, its photographic applications are regarded as having the most importance, and have been chiefly considered in deciding upon the different changes and improvements which have been made.

The interior of the dome is lighted at night by a large lamp, which is enclosed in a suitable box or lantern, fitted with panes of red glass, and mounted on a portable stand. In order to diffuse the light in the lower part of the dome, where most of the assistant’s work is done, the walls are painted bright red; while to prevent reflected light from reaching the photographic plate, the inner surface of the dome itself, the mounting, and the ladders and gallery are painted dead black. The observer is therefore in comparative darkness, and not the slightest fogging of the plate, from the red light below, is produced during a four-hours’ exposure. On the few occasions when orthochromatic plates are used the lamp need not be lighted.

Experiments have shown that the fogging of the photographic plate, during a long exposure, is entirely due to diffuse light from the sky, and is therefore unavoidable. For this reason the cloth curtains which lace to the corners of the telescope tube, enclosing it and shutting out light from the lower part of the dome, have not been used, since their only effect would be to catch the wind and cause vibrations of the telescope. They would probably have little effect on the definition, and at any rate could not be expected to improve it.

For photographing stars and nebulæ the Crossley reflector is provided with a double-slide plate-holder, of the form invented by Dr. Common.[8] This apparatus, which had suffered considerably in transportation, and from general wear and tear, was thoroughly overhauled by the Observatory instrument-maker. The plates were straightened and the slides refitted. A spring was introduced to oppose the right ascension screw and take up the lost motion—the most annoying defect that such a piece of apparatus can have—and various other improvements were made, as the necessity for them became apparent. They are described in detail farther below.

The present appearance of the eye-end is shown in the illustration. The plate-holder is there shown, however, on one side of the tube, and its longer side is parallel to the axis of the telescope. This is not a good position for the eye-end, except for short exposures. In practice, the eye-end is always placed on the north or south side of the tube, according as the object photographed is north or south of the zenith. The right ascension slide is then always at right angles to the telescope axis, and the eye-end can not get into an inaccessible position during a long exposure.

As the original wooden plate-holders were warped, and could not be depended upon to remain in the same position for several hours at a time, they were replaced by new ones of metal, and clamping screws were added, to hold them firmly in place. The heads of these screws are shown in the plate, between the springs which press the plate-holder against its bed.

To illuminate the cross-wires of the guiding eyepiece, a small electric lamp is used, the current for which is brought down from the storage battery at the main Observatory. The coarse wires have been replaced by spider’s webs,[9] and reflectors have been introduced, to illuminate the declination thread. A collimating lens, placed at its principal focal distance from the incandescent filament of the lamp, makes the illumination of the wires nearly independent of their position on the slide, and a piece of red glass, close to the lens, effectually removes all danger of fogging the plate. The light is varied to suit the requirements of observation by rotating the reflector which throws the light in the direction of the eyepiece.

DOUBLE-SLIDE PLATE-HOLDER OF THE CROSSLEY REFLECTOR.

In long exposures it is important for the observer to know at any moment the position of the plate with reference to its central or zero position. For this purpose scales with indexes are attached to both slides; but as they can not be seen in the dark, and, even if illuminated with red light, could not be read without removing the eye from the guiding eyepiece, I have added two short pins, one of which is attached to the lower side of the right ascension slide, and the other to its guide, so that the points coincide when the scale reads zero. These pins can be felt by the fingers, and with a little practice the observer can tell very closely how far the plate is from its central position. It would not be a very difficult matter to improve on this contrivance, say by placing an illuminated scale, capable of independent adjustment, in the field of the eyepiece, but the pins answer every purpose. The declination slide is changed so little that no means for indicating its position are necessary.

In this apparatus, as originally constructed, the cross-wires of the guiding eyepiece were exactly in the plane of the photographic plate. The earlier observations made with the Crossley reflector on Mount Hamilton showed that this is not the best position of the cross-wires. The image of a star in the guiding eyepiece, which, when in the middle of its slide, is nearly three inches from the axis of the mirror, is not round, and its shape varies as the eyepiece is pushed in or drawn out. In the plane of the photographic plate (assumed to be accurately in focus), it is a crescent, with the convex side directed toward the center of the plate. This form of image is not suitable for accurate guiding. Outside this position the image changes to an arrow-head, the point of which is directed toward the axis, and this image can be very accurately bisected by the right ascension thread. As the construction of the apparatus did not allow the plane of the cross-wires to be changed, the wooden bed of the plate-holder was cut down, so as to bring the wires and the plate into the proper relative positions.

After some further experience with the instrument, still another change was made in this adjustment. It was found that the focus often changed very perceptibly during a long exposure, and while the arrow-head image above described was suitable for guiding purposes, its form was not greatly affected by changes of focus. Between the crescent and the arrow-head images there is a transition form, in which two well-defined caustic curves in the aberration pattern intersect at an acute angle. The intersection of these caustics offers an excellent mark for the cross-wires, and is at the same time very sensitive to changes of focus, which cause it to travel up or down in the general pattern. The bed of the plate-holder was therefore raised, by facing it with a brass plate of the proper thickness.

Why the focus of the telescope should change during a long exposure is not quite clear. The change is much too great to be accounted for by expansion and contraction of the rods forming the tube, following changes of temperature, while a simple geometrical construction shows that a drooping of the upper end of the tube, increasing the distance of the plate from the (unreflected) axis of the mirror, can not displace the focus in a direction normal to the plate, if it is assumed that the field is flat. The observed effect is probably due to the fact that the focal surface is not flat, but curved. During a long exposure, the observer keeps the guiding star, and therefore, very approximately, all other stars, in the same positions relatively to the plate; but he has no control over the position of the axis of the mirror, which, by changes of flexure, wanders irregularly over the field. The position of maximum curvature, therefore, also varies, and with it the focus of the guiding star relatively to the cross-wires, where the focal surface is considerably inclined to the field of view. It is certain that the focus does change considerably, whatever the cause may be, and that the best photographic star images are obtained by keeping the focus of the guiding star unchanged during the exposures. This is done by turning the focusing screw of the eye-end.

In making the photographs of nebulæ for which the Crossley telescope is at present regularly employed, it was at first our practice to adjust the driving-clock as accurately as possible to a sidereal rate, and then, when the star had drifted too far from its original position, on account of changes of rate or of flexure, to bring it back by the right-ascension slow motion, the observer either closing the slide of the plate-holder or following the motion of the star as best he could with the right-ascension screw. Lately a more satisfactory method, suggested by Mr. Palmer, has been employed. The slow motion in right ascension is of Grubb’s form,[10] and the telescope has two slightly different rates, according to whether the loose wheel is stopped or allowed to turn freely. The driving-clock is adjusted so that one of these rates is too fast, the other too slow. At the beginning of an exposure the wheel is, say, unclamped, and the guiding star begins to drift very slowly toward the left, the observer following it with the screw of the plate-holder. When it has drifted far enough, as indicated by the pins mentioned farther above, the wheel is clamped. The star then reverses its motion and begins to drift toward the right; and so on throughout the exposure. The advantages of this method over the one previously employed are, that the star never has to be moved by the slow motion of the telescope, and that its general drift is in a known direction, so that its movements can be anticipated by the observer. In this way photographs are obtained, with four hours’ exposure, on which the smallest star disks are almost perfectly round near the center of the plate, and from 2″ to 3″ in diameter.

The star images are practically round over a field at least 1 inch or 16′ in diameter. Farther from the center they become parabolic, but they are quite good over the entire plate, 3¼ by 4¼ inches.

From these statements it will be seen that small irregularities in driving no longer present any difficulties. But certain irregular motions of the image still take place occasionally, and so far it has not been possible entirely to prevent their occurrence.

It was found that the declination clamp (the long slow-motion handle attached to which is shown in the illustration) was not sufficiently powerful to hold the telescope firmly during a long exposure. A screw clamp was therefore added, which forces the toothed-declination sector strongly against an iron block just behind it, thus restoring, I think, the original arrangement of the declination clamp as designed by Dr. Common. This clamp holds the tube very firmly.

The irregularities to which I have referred consist in sudden and unexpected jumps of the image, which always occur some time after the telescope has passed the meridian. These jumps are sometimes quite large—as much as one-sixteenth of an inch or 1. They are due to two causes: flexure of the tube, and sliding of the mirror on its bed. When the jump is due to sudden changes of flexure, the image moves very quickly, and vibrates before it comes to rest in its new position, and at the same time there is often heard a slight ringing sound from the tension rods of the tube. There seems to be no remedy for the sudden motions of this class. The tension rods are set up as tightly as possible without endangering the threads at their ends or buckling the large corner tubes. A round telescope tube, made of spirally-wound steel ribbon riveted at the crossings, would probably be better than the square tube now in use.

Jumps due to shifting of the mirror are characterized by a gentle, gliding motion. They can be remedied, in part, at least, by tightening the copper bands which pass around the circumference of the mirror within its cell. This will be done the next time the mirror is resilvered.

All that the observer can do when a jump occurs is to bring back the image as quickly as possible to the intersection of the cross-wires. If all the stars on the plate are faint, no effect will be produced on the photograph; but stars of the eighth magnitude or brighter will leave short trails. The nebula, if there is one on the plate, will, of course, be unaffected.

Before beginning an exposure the focus is adjusted by means of a high-power positive eyepiece. An old negative, from which the film has been partially scraped, is placed in one of the plate-holders, and the film is brought into the common focus of the eyepiece and the great mirror. The appearance of the guiding star, which varies somewhat with the position of the guiding eyepiece on its slide, is then carefully noted, and is kept constant during the exposure by turning, when necessary, the focusing screw of the eye-end. For preliminary adjustments a ground-glass screen is often convenient. On it all the DM. stars, and even considerably fainter ones, as well as the nebulæ of Herschel’s Class I, are easily visible without a lens.

Plates are backed, not more than a day or two before use, with Carbutt’s “Columbian backing,” which is an excellent preparation for this purpose. During the exposure the observer and assistant exchange places every half hour, thereby greatly relieving the tediousness of the work, though two exposures of four hours each, in one night, have proved to be too fatiguing for general practice. At the end of the first two hours it is necessary to close the slide and wind the clock.

The brightness of the guiding star is a matter of some importance. If the star is too bright, its glare is annoying; if it is too faint, the effort to see it strains the eye, and changes of focus are not easily recognized. A star of the ninth magnitude is about right. In most cases a suitable star can be found without difficulty.

In such an apparatus as that described above, the amount by which the plate may be allowed to depart from its zero position is subject to a limitation which has not, I think, been pointed out, although it is sufficiently obvious when one’s attention has been called to it. It depends upon the fact that the plate necessarily moves as a whole, in a straight line which is tangent to a great circle of the sphere, while the stars move on small circles around the pole. The compensation for drift, when the plate is moved, is therefore exact at the equator only.

Let the guiding star have the declination δ1, and let a star on the upper edge of the plate (which, when the telescope is north of the zenith, and the eye-end is on the north side of the telescope, will be the southern edge) have the declination δ2. Then if the guiding star is allowed to drift from its zero position through the distance d, the other star will drift through the distance d (cos δ2 / cos δ1). If the guiding star is followed by turning the right-ascension screw, the upper edge of the plate, as well as the guiding eyepiece, will be moved through the distance d. Hence there will be produced an elongation of the upper star, represented by

e = d (cos δ2 — 1)
cos δ1
from which d = e cos δ1 .
cos δ2 - cos δ1

Now, in the Crossley reflector, the upper edge of the plate and the guiding eyepiece are just about 3⅔ inches, or 1°, apart. If e is given, the above formula serves to determine the maximum range of the slide for different positions of the telescope.

It has been stated farther above that the smallest star disks, on a good photograph, are sometimes not more than 2″ in diameter, or in a linear measure, about 1⁄20 mm. An elongation of this amount is therefore perceptible. There are many nebulæ in high northern declinations, and there are several particularly fine ones in about +70°. If, therefore, we take δ2 = 70°, δ1, = 71°, e = 0.05, and substitute these values, we find d = 1.0 mm, which is the greatest permissible range of the plate in photographing these nebulæ. Before I realized the stringency of this requirement, by making the above simple computation, I spoiled several otherwise fine negatives by allowing the plate to get too far from the center, thus producing elongated star images.

There is a corresponding elongation in declination, the amount of which can be determined by an adaptation of the formula for reduction to the meridian, but it is practically insensible.

On account of the short focal length of the three-foot mirror, the photographic resolving power of the telescope is much below its optical resolving power. For this reason the photographic images are less sensitive to conditions affecting the seeing than the visual images. On the finest nights the delicate tracery of bright lines or caustic curves in the guiding star is as clear and distinct as in a printed pattern. When the seeing is only fair these delicate details are lost, and only the general form of the image, with its two principal caustics, is seen. A photograph taken on such a night is not, however, perceptibly inferior to one taken when the seeing is perfect. When, however, the image is so blurred that its general form is barely distinguishable, the photographic star disks are likewise blurred and enlarged, and on such nights photographic work is not attempted.

The foregoing account of the small changes which have been made in the Crossley telescope and its accessories may appear to be unnecessarily detailed, yet these small changes have greatly increased the practical efficiency of the instrument, and, therefore, small as they are, they are important. Particularly with an instrument of this character, the difference between poor and good results lies in the observance of just such small details as I have described.

At present the Crossley reflector is being used for photographing nebulæ, for which purpose it is very effective. Some nebulæ and clusters, like the great nebula in Andromeda and the Pleiades, are too large for its plate (3¼ × 4¼ in.), but the great majority of nebulæ are very much smaller, having a length of only a few minutes of arc, and a large-scale photograph is required to show them satisfactorily. It is particularly important to have the images of the involved stars as small as they can be made.

Many nebulæ of Herschel’s I and II classes are so bright that fairly good photographs can be obtained with exposures of from one to two hours; but the results obtained with full-light action are so superior to these, that longer exposures of three and one half or four hours are always preferred. In some exceptional cases, exposures of only a few minutes are sufficient. The amount of detail shown, even in the case of very small nebulæ, is surprising. It is an interesting fact that these photographs confirm (in some cases for the first time) many of the visual observations made with the six-foot reflector of the Earl of Rosse.

Incidentally, in making these photographs, great numbers of new nebulæ have been discovered. The largest number that I have found on any one plate is thirty-one. Eight or ten is not an uncommon number, and few photographs have been obtained which do not reveal the existence of three or four. A catalogue of these new objects will be published in due time.

Some of the results obtained with the Crossley reflector, relating chiefly to particular objects of some special interest, have already been published.[11] The photographs have also permitted some wider conclusions to be drawn, which are constantly receiving further confirmation as the work progresses. They may be briefly summarized as follows:

1. Many thousands of unrecorded nebulæ exist in the sky. A conservative estimate places the number within reach of the Crossley reflector at about 120,000. The number of nebulæ in our catalogues is but a small fraction of this.

2. These nebulæ exhibit all gradations of apparent size, from the great nebula in Andromeda down to an object which is hardly distinguishable from a faint star disk.

3. Most of these nebulæ have a spiral structure.

To these conclusions I may add another, of more restricted significance, though the evidence in favor of it is not yet complete. Among the objects which have been photographed with the Crossley telescope are most of the “double” nebulæ figured in Sir John Herschel’s catalogue (Phil. Trans., 1833, Plate XV). The actual nebulæ, as photographed, have almost no resemblance to the figures. They are, in fact, spirals, sometimes of very beautiful and complex structure; and, in any one of the nebulæ, the secondary nucleus of Herschel’s figure is either a part of the spiral approaching the main nucleus in brightness, or it can not be identified with any real part of the object. The significance of this somewhat destructive conclusion lies in the fact that these figures of Herschel have sometimes been regarded as furnishing analogies for the figures which Poincaré had deduced, from theoretical considerations, as being among the possible forms assumed by a rotating fluid mass; in other words, they have been regarded as illustrating an early stage in the development of double star systems. The actual conditions of motion in these particular nebulæ, as indicated by the photographs, are obviously very much more complicated than those considered in the theoretical discussion.

While I must leave to others an estimate of the importance of these conclusions, it seems to me that they have a very direct bearing on many, if not all, questions concerning the cosmogony. If, for example, the spiral is the form normally assumed by a contracting nebulous mass, the idea at once suggests itself that the solar system has been evolved from a spiral nebula, while the photographs show that the spiral nebula is not, as a rule, characterized by the simplicity attributed to the contracting mass in the nebular hypothesis. This is a question which has already been taken up by Professor Chamberlin and Mr. Moulton of the University of Chicago.

The Crossley reflector promises to be useful in a number of fields which are fairly well defined. It is clearly unsuitable for photographing the Moon and planets, and for star charting. On the other hand, it has proved to be of value for finding and photographically observing asteroids whose positions are already approximately known.

One of the most fruitful fields for this instrument is undoubtedly stellar spectroscopy. Little has been done in this field, as yet, with the Crossley reflector, but two spectrographs, with which systematic investigations will be made, have nearly been completed by the Observatory instrument-maker. One of these, constructed with the aid of a fund given by the late Miss C. W. Bruce, has a train of three 60° prisms and one 30° prism, and an aperture of two inches; the other, which has a single quartz prism, will, I have reason to expect, give measurable, though small, spectra of stars nearly at the limit of vision of the telescope.

The photogravure[12] of the Trifid nebula, which accompanies this article, was made from a photograph taken with the Crossley reflector on July 6, 1899, with an exposure of three hours. It was not selected as a specimen of the work of the instrument, for the negative was made in the early stages of the experiments that I have described, and the star images are not good, but rather on account of the interest of the subject. At the time the photogravures were ordered no large scale photograph of the Trifid nebula had, so far as I am aware, ever been published.[13] The remarkable branching structure of the nebula is fairly well shown in the photogravure, though less distinctly than in the transparency from which it was made. The enlargement, as compared with the original negative, is 2.9 diameters (1 mm = 13″). The fainter parts of the nebula would be shown more satisfactorily by a longer exposure.

List of Nebulæ and Clusters Photographed.

N.G.C. No.α 1900.0δ 1900.0Remarks.
hms°′
18503325+4747.3H II, 707
20503456+418.2H V, 18
22103715+4019.0M 32
22403717+4043.4Great nebula in Andromeda
2470423-2117.9H V, 20
25304236-2550.6H V, I
52411933+ 91.0H I, 151
59812812+308.6M 33
62813119+1516M 74
6501360+514.0M 76
89121615+4153.6H V, 19
10232348+3838.0H I, 156
106823734- 026.3M 77
10842415- 80.0H I, 64
...341 +24 Pleiades in Taurus
15554168+1917T Tauri and Hind’s variable nebula
193152448+3410.1H I, 261
195252830+2157Crab nebula in Taurus
...530 - 5 Great nebula in Orion
197753027- 454.2H V, 30
202453648- 154.3H V, 28
206854137+ 00.8M 78
223962537+ 51.1Cluster and nebula in Monoceros
2264635 +100Nebula near 15 Monocerotis
228764243-2038.4M 14
...65940-1018.2New nebula in Monoceros
235971254-132.0H V, 21
236671818+6913.4H III, 748
2371-27196+2941.0H II, 316-7
24037279+6548.9H V, 44
243773524-1435.3Cluster and nebula M 46
2632834 +20 Præsepe cluster
268384629+3347.8H I, 200
28419156+5124H I, 205
2903-0592631+2157H I, 56-57
300394238+3352.8H V, 26
303194718+6932M 81
30799559+5610.1H V, 47
311510016- 714.0H I, 163
31691094+ 357.7H I, 4
3184101215+4155.1H I, 168
3198101342+463.7H I, 199
3226-7101759+2024.1H II, 28-29
3242101929-185H IV, 27
...10217+6858New nebula in Ursa Major (Coddington).
355611540+5613.0H V, 46
35871190+5533.7Owl nebula, M 97
3623 111343+1338.4M 65
362711151+1332M 66
3726112756+4735.8H II, 730
4244121229+3822.0H V, 41
4254121345+1459M 99
425812142+4751.6H V, 43
4303121618+ 51.7M 61
4321121752+1622.7M 100
4382122021+1844.7M 85
4485-90122540+4215.3H I, 197-198
4501122656+1458.5M 88
4536122920+ 244.2H V, 2
4559123059+2830.6H I, 92
4565123124+2632.2H V, 24
4631123719+335.9H V, 42
4656-5712396+3242.8H I, 176-7
4725124533+263H I, 84
4736124613+4139.5M 94
4826125149+2213.9M 64
5055131120+4233.6M 63
5194-5132539+4742.6M 51
5247133239-1722.4H II, 297
5272133735+2853M 3
5457-8135939+5450M 101
5857-915255+1958.9H II, 751-2
586615345+569.0H I, 215
5904151329+ 227M 5
620516386+3639.0M 13
621816422- 146.2M 12
6412173241+7547.3H VI, 41
6514175543-232Trifid nebula in Sagittarius
6523175743-2423M 8
6543175835+6638H IV, 37
661818150-1613M 17 Omega nebula
6656183017-2359.3M 22
6705184542- 623.3M 11
6720184953+3254.0M 57
6853195517+2227Dumb-Bell nebula
6894201222+3015.5H IV, 13
6946203248+5948.0H IV, 76
6951203547+6545.4
699520530+3049.8
7008205738+549.5H I, 192
7009205811-1148H IV, 1
702321030+6746.2H IV, 74
707821259+1143.7M 15
7089212819- 116.0M 2
7099213442-2338.0M 30
721722324+3052.3H II, 207
7331223230+3353.9H I, 53
744822557+1526.6H II, 251
7479225956+1147.0H I, 55
7537-4123938+ 359.4H II, 429-30
766223215+4159.2H IV, 18
7782234847+ 724.8H III, 233
781423588+1534.5H II, 240
7817235852+2011.6H II, 227

Catalogue of New Nebulæ Discovered on the Negatives.

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
10027.4+3.0732+203457+20.048vS eeF
20327.73.2795+47552919.855eF N
30328.13.2801+4812219.855F vbM E140°
40329.33.2776+47372419.855eF bM
503228.83.2799+4739519.851B vE70°
603323.93.2674+4755519.841eF vS
703543.13.3009+47461819.810eF vS
804051.12.9793-21254819.73018 vS R
90470.12.9804-2191719.72716 vS bM 3 sep. parts
1004116.22.9781-21294319.72318 vS R bM
1104116.72.9792-2115219.72318 vS R
1204129.72.9798-213819.71918 vS bM E50°
130424.42.9633-260719.71117 vS R bsw
1404230.72.9780-20563819.70318 vS bM E115°
1504234.22.9620-25591019.70217 vS N E160°
1604237.62.9776-20582819.70114 S E stell N
1704239.72.9772-2115419.70117 vS Spiral bM
1804239.92.9774-210319.70018 vS Ring?
1904240.52.9770-2135519.70015 S Spiral N bM
2004240.62.9762-21135419.70018 vS R
2104310.42.9603-25593619.69218 vS R bM
2204316.22.9730-21371719.69118 vS dif
2304327.12.9613-25402119.68817 vS R N
2404329.02.9593-2605719.68718 vS R gbM
2504410.82.9714-21302919.67618 vS R
2604426.62.9735-20583519.67217 vS R bM
2711830.93.1475+ 9272518.887F S N
2811853.53.1475+ 9242818.875F vbM Spiral?
2911911.33.1474+ 9215318.867F vbM Spiral?
3011930.73.1467+ 9141818.857F bM E
3112950.73.2101+1563718.526pF E45° bp
3212954.43.2161+15432518.524F R
3313020.93.2127+15173818.509vF L R
3413024.73.2132+15202818.507pF S vF extension 135°
3513035.93.2153+1532218.501S pB pmb M
3613054.73.2176+1543118.491vvF vS
371315.03.2179+15433818.485F S E95°
3813115.93.2159+15304418.478pF S R
3913125.73.2187+15443418.473vF S R
4013144.83.2194+15464918.462F L R gbM
4113144.83.2126+1541818.462F L gbM R
421325.93.2158+15205418.450S pB E135°
4313241.33.2171+15232218.430vF S E45°
4413248.83.2156+15122718.424vF pL
4513310.43.2168+15164918.413vF pL gbM
4613313.23.2166+15151418.412p B R gbM
4721410.23.7341+4150816.715pF E135°
4821426.63.7349+4149116.701pB N R
4921433.93.7307+41373116.696B N
5021436.73.7313+41382416.694F
5121455.03.7506+42242016.677eF vS bM E135°
522156.23.7517+4225616.668F gbM E130° Spiral?
5321514.93.7493+42164416.661F pmbM
5421516.13.7484+4214416.659F B*f
5521538.43.7666+4255016.641eF vS R
5621543.83.7503+42135816.637S F R
5721556.53.7724+4352416.626F E170° bsf
582161.03.7539+42205516.623B S vbM E150° bnp
592166.43.7403+41445116.619S F R
602169.73.7408+41452616.616F S pmbM
6121613.03.7613+42363216.613pB vbM E150° Spiral?
6221631.13.7640+42392716.598eeF E50°
6321634.53.7412+4142616.595pB pmbM
6421640.33.7620+42332216.591B S pbM
6521643.33.7403+41381416.588pB E0° pmbM
6621653.23.7625+42321216.580vB S mbM
6721657.83.7567+42164816.576F triN npN
6821713.8+3.7403+422237+16.563pB bs B*p

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
6921718.9+3.7661+423612+16.559pS pB gbM E40°
7021728.53.7415+4133316.551pF S R
7121728.83.7560+4293516.551vF
7221733.23.7606+42201716.547F vS bnp
7321736.23.7789+4332516.545eeF S
7421737.23.7469+4145216.544F vL vmbM
7521741.83.7592+4215816.540S pB bs
7621743.33.7554+4252116.539F bsp
7721744.63.7441+42182816.538B S E90° bM
7821745.53.7425+42224516.537F L bM N B*np
7921750.83.7743+42502016.533pB gbM E135°
8021751.13.7484+41462216.532pB E135° gbM
812180.23.7743+42483016.525vF pL gbM E50°
822180.83.7502+41485516.525pF L
832184.23.7603+4214016.522S B vbM
8421814.83.7579+4272716.513pB E150° Spiral
8521823.63.7792+42561016.507eeF pL E120°
8621826.73.7604+4210816.503vB E45°
8721830.73.7465+41341316.499F E150° bnf
8821833.53.7784+42521916.498B S gbM
8921834.03.7628+42144416.497vS vF bsp
9021837.43.7837+4342616.495S F bs
9123151.33.7209+38163015.806vF vS
9223353.93.7295+38192715.694F vS N
9323356.73.7461+38491515.691F S bn E0° long N
942347.53.7405+3843415.681pF S i triN
952349.23.7399+38431015.680pF vS
9623411.83.7259+3873915.678F L E40° Spiral on edge
9723444.23.7402+38382715.648eeeF doubtful
9823444.43.7488+38161615.648pB N E50° S pmbM
992351.03.7469+38184515.632L F pmbM
10023632.93.7436+38302615.548S F E100°
10123653.33.0662- 0244815.525vS vF gbM
1022376.03.0728- 024315.518vS F m E30°
10323844.23.0688- 0162015.427F S m E80°
10424111.62.9503- 831715.294pB vS E135°
10524153.72.9564- 738915.254vF vS mbM
10624218.92.9499- 822715.230eeF S
10743522.93.0244- 212207.23516 S E165° Dif bM
1084360.63.0307- 154377.18318 vS R
1094363.63.0300- 156427.17917 vS R stell
11043612.73.0337- 146197.16716 vS nearly R bM
11143615.23.0238- 213387.16418 vS R (Spiral?)
11243640.53.0251- 29537.12918 vS R N
11343641.23.0293- 158237.12818 vS E30° bn
1144372.43.0268- 25107.09918 vS dif
11543726.83.0298- 156517.06615 vS Spiral B N (stell)
11652448.13.9674+34628+ 3.075bright stell N on north side
1177140.76.4903+693920- 6.36217 vS bM
11871424.56.4656+6931496.39517 vS N Ring
11971437.56.4241+6918156.41317 R bM
12071545.66.4282+6921356.50717 vS
12171550.76.4875+6941266.51416 vS R
1227164.16.4719+6936406.53217 vS E125° D?
1237168.06.4219+692046.53818 vS E70°
12471635.26.4099+6916466.57516 vS iF
12571648.06.4578+6933166.59317 vS R
1267179.16.4119+6918256.62218 vS R
12771738.56.4906+6945296.66217 vS bM R
12871745.36.4750+6940366.67217 vS R bM
12971749.63.7911+2941496.67718 vS F*inv dif
13071749.76.4843+6943466.67817 vS E135° bM N Spiral
13171811.16.4754+6941286.70716 vS dif 2 or 3 N
13271814.43.7838+2927416.71118 vS iF N
13371820.13.7840+2928206.71918 vS bM
13471821.13.7950+2951186.72118 vS bM
13571842.23.7832+2927236.74918 vS iF sc
13671851.06.6430+6938326.76317 vS E80° bM N Spiral on edge
13771856.53.7827+292776.76919 vS
13871910.0+3.7819+29267- 6.78818 vS R bM N Spiral?

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
13971911.6+3.7800+292212- 6.79018 vS bM
14071911.86.4683+6940546.79015 vS Neb*
14171925.26.4609+6938506.80916 vS R bM N Spiral?
14271930.03.7874+2938226.81618 vS 2N R
14371934.06.4629+6939466.82117 vS R
14471946.53.7859+2935586.83918 vS bM N R
14571948.33.7866+2937216.84118 vS R bM
14672113.46.4694+6944516.95717 vS R bM N Spiral?
14772157.96.4648+6944427.01817 vS bM N R Spiral?
1487248.05.8308+6539287.198pB E200° bn
14973037.25.8297+6553167.720vF vS
15073110.95.8139+654707.767pB S gpmbM
15183238.83.4536+19563712.38716 S E10° stell N M (Spiral on edge?)
15283240.23.4534+1956012.38817 E95° S dif
15383411.63.4527+19595012.493s17 vS E30° stell N Spiral?
15483528.93.4520+2024712.58117 S Spiral N
1558367.43.4514+2033312.62417 S R bM N
15684440.53.7549+34132113.203eF E140°
1578461.93.7442+33505713.290vF vS
15884626.83.7403+33442613.318F vS N E120° Spiral
15984652.63.7397+33451913.345pB eS N R
16084720.63.7507+34144313.376eF eS bf
16184756.93.7509+34184113.415eeF
1629120.04.2083+51472014.898L 12 m E135°
1639122.14.2062+51443214.90416 E80° bs S
16491212.54.2001+51365414.91017 vS Ring bs
16591238.04.1950+51314314.93916 E155° gbm
16691240.44.1862+5118014.93616 vS E15° stell N
16791245.44.1835+51163414.94216 E75° vbN Spiral?
16891354.34.1814+51224515.00918 vS N bM
1699140.54.1839+51265315.01618 vS scNuclei
17091523.94.1662+51114615.09117 vS R
17191524.64.1652+51101215.09117 vS bN Ring or Spiral
17291529.34.1658+51115915.09617 S R
17391544.64.1631+51112615.11115 B bM E145°
1749166.34.1821+51421115.13617 R S
17591614.64.1638+51154215.14217 L vF bM
17691631.64.1528+51463215.16817 R S bs
17792420.23.4095+21495015.597vF vS
17892436.83.4084+2148615.612pB bs S
17992558.53.4047+21452515.687eF E85°
18092622.53.4046+21485015.711pB S R gpmbM N
1819280.23.4020+21523615.801eeF vS
1829413.63.5855+33582416.47416 vS bM E75°
1839419.93.5850+33581216.48015 vS sbM Spiral
1849429.03.5779+33454916.52817 vS N Spiral?
18594249.53.5822+3461116.56116 vS bM
18694312.43.5805+3444316.58015 vS sbM N Spiral
18794329.23.5789+3422616.59416 vS bnw R
18894413.03.5764+342716.63014 vS bM N Spiral
18994424.63.5760+343116.64016 vS R N Spiral?
19094444.43.5668+33372716.65617 vS E20°
19194452.85.0574+69281316.670pB vS R gpmbM
1929475.74.9895+6952716.776pF S bf E90°
19394722.24.9858+6952516.790vF dif
19495019.44.9915+69304016.930pF S E120°
19595052.84.9930+69352616.955eeF S E120°
19695059.15.0068+6944016.959pB S E50° pmbM Spiral
19795229.24.9219+6965117.039eF E100°
1989544.14.1109+5655317.09611 vS neb*
19995424.74.1167+56183817.11118 vS R
20095426.54.1121+56115317.11315 vS E95° bM
20195514.04.1162+56271317.14817 vS R
20295646.24.0872+5601817.21917 vS R bM
20395729.54.0952+56203317.25015 vS R N
20410015.32.9839- 7333417.37217 vS sbN Spiral
20510040.42.9909- 6592517.39117 vS stell sbN
2061042.82.9850- 7295017.39211 S D iF gbN bn
20710149.72.9891- 7121117.44117 vS stell
20810650.1+3.1101+ 35057-17.65314 vS D neb*

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
20910718.1+3.1112+ 4530-17.67116 vS iF bM
21010718.53.1112+ 442517.67216 vS bM N Spiral E50°
21110758.43.1128+ 3584417.69916 vS sbM N Spiral E20°
21210820.63.1137+ 3521317.71415 S iF bM
21310940.73.1169+ 483417.76918 vS R
21410944.83.1171+ 494717.77217 vS sbM N Spiral? E45°
21510948.33.6290+4202017.77616 E95° 33″ long small spur follows E45°
21610950.23.1172+ 4105017.77617 vS bM N R
21710958.93.6294+424617.78317 vS R
21810103.03.6318+42121517.78617 vvS stell
219101015.53.6205+41395217.79315 S E60°
220101016.83.6317+42155617.795vS R stell
221101016.83.6311+4214717.79518 vvS sbN Spiral?
222101021.83.1184+ 3515217.79717 vS bM N Spiral
223101023.03.6194+41382417.79816 vS bM Spiral N
224101023.93.6208+41424717.79918 vvS R Spiral? N
225101024.53.6206+41424117.80018 vvS sbN iF
226101050.93.6230+41564517.81718 vvS iF
227101054.43.6245+4222317.81917 vS iF
228101144.03.6222+4273117.85218 vvS bn iF
229101144.03.6221+427317.85218 vvS Spiral sbN
230101147.53.6210+4242717.85417 vS sbN Spiral
231101152.13.6945+45405217.856F S R gbM bf
232101152.23.6214+4265617.85718 vvS iF stell
23310126.23.6114+41365017.86110 S neb*
234101221.83.6231+42195517.87817 vS sbN Spiral
235101229.13.6192+4285417.88217 vS sbN Spiral
236101231.53.6204+42131617.88316 vS stell
237101233.43.6184+4274617.88418 vS E100° Spiral?
238101241.53.6939+45513417.890eeeF??
239101243.23.6150+4159817.89117 vS sbM N
240101243.53.6168+4251617.89116 vvS bN stell
241101248.13.6940+45534117.894F vS R gbM
242101250.63.6940+45541117.896F S E90°
243101251.33.6163+4252317.89718 vvS R stell
244101257.83.6136+41583917.90118 vvS iF
24510130.43.6212+4223517.90216 vS iB N Spiral E30°
24610134.13.6999+46141717.905B S E130° Spiral on edge
247101310.13.7010+46185017.909B R vm bM
248101319.73.6960+4671517.915eF S R bM
249101333.83.6170+42172817.92418 vS stell
250101337.13.6054+41423917.92717 vS Spiral stell N
251101344.23.6159+42161717.92917 vS R gbN
252101346.03.6110+4211517.93317 vvS gbN Spiral N
253101348.53.6972+46175717.934F S E170° Spiral?
254101353.93.6036+4141117.93818 vS sbN
255101354.53.6107+4233117.93817 vS R gbN
256101357.93.6103+423517.94017 vS iF gbN
25710140.03.6032+4141917.94218 vvS iF
25810145.53.6812+4537117.944vF vvS R
259101411.53.6113+4291017.94918 vvS bN Spiral
260101412.53.6113+4294417.94917 vS sbN Spiral
261101424.23.6104-4294217.95819 vvS iF E130°
262101426.83.6865+45572717.958B S E45°
263101433.03.6785+45363927.962vF vS E100°
264101435.73.6250+4203117.96517 vS Spiral N E100°
265101446.33.6916+46164017.972vvF E100° spindle shaped
266101452.33.6779+45395917.975vF S R
267101522.53.6866+46114017.995F R S gbM
268101617.43.6765+4557918.031F S R gbM
269101627.14.5844+68531018.038S pB bf
270101637.13.6761+461118.044F pmbM E10°
27110178.03.2872+20194618.06213 vS sbM N Spiral E135°
272101712.73.2868+20181618.06513 vS gbM Spiral
273101719.63.2865+20174718.07014 vS gbN
274101747.13.2899+20405818.08715 vS iF gbM
275101753.63.2880+20315718.09114 S sbM N Spiral E130°
27610187.13.2906+20472518.10013 vS sbM N Spiral
27710195.23.2870+20384218.13613 S sbM N Spiral
27810196.9+3.2857+203221-18.13716 vS iF gbM

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
279101910.3+3.2885+204738-18.13914 vS stell
280101920.64.5635+6995118.149S pF R
28110246.24.4863+68593118.317vS F E95°
28211152.73.5701+5559019.40716 vS bN iF
2831125.83.5753+56251619.41215 vS neb*
2841129.53.5660+55533119.41316 S gbM E100°
28511222.63.5740+56282919.41915 vS stell
28611254.63.5647+56114319.42915 vS sbM stell N
2871138.03.5613+5662619.43517 vS N
28811312.33.5620+56111719.43516 vS sbN R Spiral?
28911322.73.5523+55584319.43914 vS neb*
29011432.23.5510+5612919.46317 vS stell
29111444.83.5467+564919.46715 S R sbM N Spiral
29211447.73.5469+5654019.46817 vS R neb*
29311457.33.5437+55591619.47117 vS stell
2941156.23.5426+5602619.474Two 18 mag. objects, iF, close together
29511516.13.5379+55485819.47816 vS. Uniform brightness
29611520.83.5431+5684619.47917 vS iF stell
29711522.13.5373+55492019.48015 vS R gbM N Spiral
29811535.23.5408+5681819.48416 vS R gbM
29911542.33.5387+5643319.48718 vS sbM N Ring
30011550.53.5412+56165819.49017 vS sbM N Spiral?
30111554.83.5299+55401119.493vvF E75°
30211558.23.5290+55373319.494S vF R
3031161.63.5352+5613919.49416 vS R sbM N Spiral
3041166.13.5322+55535119.49517 vS gbM iF
3051168.83.5347+5632319.49617 S vm E85°
30611612.53.5292+55452219.499vF E100° spindle shaped
30711619.13.5312+55563719.50017 vS dif
30811623.73.5305+55564419.501vS iF dif
30911627.13.5300+55564019.50217 vS gbM iF
31011628.43.5303+5558419.50316 vS sbM N Spiral
31111642.03.5330+56133319.50716 vS bM E150°
31211643.03.5297+5631319.50817 vS dif iF
31311645.03.5298+5641819.50817 vS dif iF
31411651.13.5313+56122419.51017 vS sbM N Spiral
31511655.43.5262+55571119.51216 vS R sbM N Spiral
3161176.73.5295+56133619.51613 S sbM N Spiral E70°
31711710.±...+56140±...16 vS stell iF neb?
31811715.93.5304+5621919.51915 vS R sbM N Spiral
31911723.93.5248+5655819.52215 vS neb*
32011732.43.5239+567119.52516 vS sbM N Spiral
32111757.53.5230+56155819.53316 vS gbM E25°
32211759.63.5172+55574719.53416 vS neb*
3231181.83.5117+55361719.534pB S R
3241183.43.5177+5611319.53616 vS sbM
3251184.93.5153+55512519.536S F gbM E100°
32611817.43.5200+56151819.54012 S gbN be Spiral E30°
32711825.03.5178+56122119.54317 vS stell
32811846.33.5117+5615819.55015 vS stell N
32911859.23.5043+55381319.553pB S E160°
33011910.73.5006+55301819.556B irr B*n
33111920.73.5034+55454219.559vS B E100° bM
33211938.03.4948+55232719.565S pF R another apparently distinct neb np
33311941.73.5046+560219.566L B pmbM R
33411956.73.4978+55434119.571vS B E135° spindle shaped
335111014.53.4873+55145719.578S B E90° gbM
336111028.93.4870+55194819.581S pF E135° companion n
337111043.83.4929+55495519.587vS F E100° bf
338111058.53.4913+55145019.592S B R vmbM
33911111.03.4817+55174719.593S B E45° bsf
34011114.23.4809+55162319.594B Spiral
341111136.53.4780+55214519.604vvF S R
342111223.83.4719+55231119.619vB S e E170°
343111321.23.1360+13153319.632B S R neb*
344111322.73.1362+13172919.633S F gbM
345112513.43.2933+4734719.818S pB N
346112640.53.3848+4739819.836vS F
34711272.83.2828+47421319.840vS F
348112710.3+3.2774+47245-19.842vS F gbM

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
349112728.6+3.2797+473854-19.846vS B vmbM Spiral
350112741.93.2757+47164819.848vS B E135°
351112818.13.2698+46592219.856vS F
352112850.23.2694+47244619.862vS B
353112923.43.2668+47323119.869vS vB N E100°
35411303.63.2603+47135619.877pS pF
355121036.73.0230+38303620.026S pB bf
356121045.33.0232+3844420.025S pB E95°
357121051.83.0218+3834320.025S pB bf
358121118.12.9996+47513620.02515 vS stell
359121127.32.9987+4749220.02415 vS E135° sbM N Spiral
360121146.72.9956+486220.02216 S E65°
361121148.52.9961+4755020.02215 vS R sbM sN Spiral
362121150.13.0176+38273420.021S vF
36312127.02.9935+4855820.02015 vS R
364121212.23.0536+14452220.01917 vS R bM
365121216.43.0529+15102620.01918 vS R
366121219.73.0532+1454620.01818 vS R
367121223.23.0527+15113420.01818 vS vF dif
368121223.53.0535+14394520.01818 vS E160°
369121225.73.0529+1514020.01818 vS R
370121236.32.9903+4852520.01716 vS dif vgbM
371121242.03.0529+14455120.01618 vS vF R
372121244.43.0530+1438820.01618 vS dif
373121245.03.0145+3757920.016S F R
374121245.62.9909+47381720.01616 vS iF
375121251.53.0526+14444220.01618 vS R bs
376121254.42.9895+47453120.01617 vS iF dif
377121254.63.0523+1454020.01518 vS E110°
378121256.23.0521+150220.01517 vS R bM
37912132.03.0519+1522820.01517 vS R N
38012135.63.0515+1515420.01418 vS vF dif
38112137.93.0518+150820.01418 vS R bM
38212139.53.0515+15124320.01417 vS R N
383121313.13.0120+3864620.014vS vF
384121330.13.0108+3844320.013S F
385121333.83.0108+37572920.013pL vF R
386121336.63.0510+1544120.01218 vS R
387121337.33.0514+14473220.01218 vS R N
388121343.83.0512+14472820.01118 vS R
389121353.13.0505+1564820.01018 vS E120°
390121353.63.0506+154020.01017 vS E100° N
391121357.43.0505+1533420.01018 vS R N
392121358.63.0510+14404420.01019 vS vF
39312145.23.0508+14411020.00918 vS R bn
39412146.23.0502+1553120.00919 vS E110° stell N
395121412.72.9815+47384520.00917 vS sbM Spiral
396121422.83.0497+1583120.00818 vS E130°
397121425.33.0499+14574820.00817 vS R N
398121431.13.0497+14585020.00718 vS R
399121444.03.0496+14505020.00618 vS R N
400121449.23.0489+15113820.00518 vS vF
40112154.93.0490+1453420.00418 vS dif
40212155.03.0492+14413020.00418 vS R two N
403121511.03.0643+ 4452220.003pF vE15°
404121511.13.0483+15133720.00317 vS E120° bM
405121522.73.0482+1564520.00217 vS R
406121531.23.0484+14473420.00218 vS E150°
407121539.33.0478+15111020.00118 vS R
408121610.53.0638+ 5111519.997F pS
409121612.43.0647+ 4375219.997vF S bn
410121631.23.0438+16321619.99516 S E0° sbM N Spiral
411121634.73.0442+1618019.99516 S sbM stell N R Spiral?
412121636.73.0442+16133019.99418 vS iF
413121649.63.0439+1612019.99317 vS gbM iF
41412173.53.0432+16211419.99118 S dif iF E135°
41512175.±3.0446+155630±19.99117 vS sbM Spiral N
41612175.23.0431+16232019.99118 vs bs R
417121712.13.0638+ 4502319.991F vS l E50°
418121714.3+3.0429+16211619.99017 vS dif gbM R

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
419121715.6+3.0430+161718-19.99016S sbM N Spiral
420121721.03.0633+ 571419.990! pB L Spiral
421121729.53.0639+ 4415319.989vF vS
422121737.03.0639+ 4411319.989vF vS 1E45°
423121757.93.0414+16273619.98517S gbM Spiral E135°
42412185.13.0633+ 4545319.986vvF vs
425121816.23.0411+16223019.98315S sbM N Spiral?
426121817.43.0409+16252219.98318vS stell N Spiral
427121819.33.0629+ 504019.983eeF S
428121834.63.0352+18544519.98118vS R diffic
429121840.43.0352+18494119.98018vS vF E160″
430121917.43.0388+16373719.97617vS R gbN Spiral
431121945.53.0333+1845119.97215vS E45° stell N
43212200.73.0399+16155719.97118 vS iF
43312209.13.0374+16385119.97017 S gbM N E60° Spiral on edge
434122010.93.0372+16402719.97017 vS R sbM N Spiral
435122021.33.0322+18414019.96818 vS R bM
436122021.83.0369+16404019.96818 vS iF dif
437122022.83.0314+1923219.96818 vS R
438122035.23.0323+18265219.96618 vS R bM
439122040.83.0307+1941619.96618 vS vF R
440122121.93.0296+18595819.96018 vS R bM
441122139.23.0296+18412919.95818 vs R
442122155.33.0297+18353719.95617 vs R bM
443122156.53.0282+1941419.95618 vS R bM
444122159.83.0290+1842019.95618 vS E120°
445122213.33.0282+1849719.95417 vS R bM
446122524.73.0336+14424619.92414 S E60°
447122535.63.0320+1583319.92218 vS dif
448122547.13.0316+15111319.92115 vS bM iF
449122549.93.0317+1561719.92016 vS gbM
450122553.03.0312+15193619.92016 S E115° bM
45112260.93.0320+14542919.91816 vS R
45212260.93.0308+1520019.91817 vS iF bM
45312264.73.0323+14485319.91818 vS iF
45412268.13.0319+14551419.91716 vS R sbM N
455122612.23.0322+14445919.91612 neb*
456122617.23.0321+14445519.91616 vS iF gbM N
457122617.33.0323+1440619.91616 vS gbM N Spiral?
458122634.73.0299+15244919.91314 S bM E165°
459122651.13.0308+14513419.91015 L m E80° bM N Spiral on edge
460122726.53.0636+ 383619.90417 vS E80° gbM Spiral on edge?
461122730.43.0634+ 3125519.90315 L vm E40° small spur from M
462122731.73.0290+1575619.90316 vS
463122731.83.0623+ 3341319.90317 vS gbM iF
464122739.23.0304+14361619.90211 L bM iF sc
465122741.63.0299+14445519.90211 neb*
466122744.23.0629+ 321019.90017 vS vgbM iF
467122745.03.0634+ 3105519.90017 vS vgbM
468122755.13.0641+ 2531319.89918 vS R (Ring?)
469122810.13.0646+ 242319.89617 vS R
470122818.23.0646+ 2422419.89416 vS ◯
471122826.53.0648+ 2504719.89317 vS E150°
472122835.93.0645+ 2412019.89117 vS E160° N
473122837.43.0272+15103219.89116 vS sbM N Spiral E50°
474122843.83.0653+ 2255319.89016 vS gbM
475122844.03.0646+ 2495219.89017 vS R bM
476122350.73.0653+ 2241919.88818 vS vF R
477122854.33.0267+15115019.88718 vS sbM N Ring?
478122855.53.0656+ 219219.88718 vS dif
479122858.53.0644+ 2415419.88718 vS E130° N
48012291.73.0653+ 2234219.88617 vS R
48112298.93.0266+1562319.88516 vS sbM N Spiral
482122915.83.0614+ 3393919.88317 vS stell
483122915.83.0615+ 3391519.88318 vS N? Spiral?
484122927.03.0635+ 258419.88118 vS dif iF
485122928.73.0636+ 371419.88117 vS sbM N Spiral
486122930.53.0650+ 2274919.88117 vS R stell N
487122940.83.0616+ 3334119.87917 vS bM N Spiral
488122942.7+3.0635+ 25534-19.87917 vS R

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
489122945.4+3.0650+ 2264-19.87817 vS E90° N
490122951.43.0620+ 3242919.87717 vS iF
491122955.33.0652+ 221019.87617 vS R N
492122956.63.0632+ 302219.87618 vS R N
493122957.13.0652+ 2201319.87617 vS R
494122958.53.0653+ 2191419.87618 vS R
49512303.32.9859+26195419.87515 vS R bM
49612304.23.0652+ 220719.87518 vS R
49712306.63.0616+ 333619.87417 vS bs iF
498123011.23.0616+ 3303619.87317 vS stell
499123012.43.0649+ 225719.87318 vS R
500123012.82.9853+26222419.87317 VS R bM
501123014.83.0648+ 2262919.87318 vS E70°
502123027.33.0648+ 2261619.87018 vS R bM
503123028.43.0648+ 2264119.87017 vS R bM
504123029.03.0651+ 2193619.87016 vS R
505123030.63.0613+ 335619.87015 L vm E165° sbM Spiral
506123032.23.0650+ 2221719.86918 vS R bM
507123035.83.0642+ 2373919.86918 vS R
508123036.82.9840+2624519.86814 S E135° N
509123039.53.0643+ 2343519.86818 vS R
510123039.73.0645+ 2295519.86818 vS R
511123042.63.0648+ 2251419.86718 vS R bM
512123043.72.9819+26501719.86717 vS E40°
513123044.22.9822+26462519.86715 vS N E50°
514123052.03.0648+ 2225619.86617 vS R
515123052.63.0619+ 3195919.86617 vS sbM Spiral E110°
516123122.52.9809+2638719.85918 vS R
517123132.72.9797+26475819.85718 vS R
518123139.62.9794+2647919.85616 vS R N
519123146.12.9796+26395119.85517 vS R N
52012326.92.9787+26382819.85017 vS R N
521123221.22.9784+26315619.84818 vS vF R
522123222.72.9777+26423619.84718 vS R bM
523122229.72.9777+26373619.84618 vS R bM
524123234.22.9780+26282419.84516 neb*
525123249.72.9758+26505919.84218 vS vF E135° D
526123541.02.9371+3374819.80516 vS E140° bM
527123634.42.9348+32561719.79217 vS R bM
528123645.32.9340+32564819.79018 vS E80°
529123654.92.9309+33242319.78717 vS E0° D
530123714.32.9303+33183519.78115 vS E125° N Spiral on edge
53112389.92.9291+32523819.77018 vS bM E140°
532123813.82.9277+3361219.76918 vS R
533123815.02.9279+3322119.76814 vS E145° bM
534123833.32.9247+3326319.76415 neb*
535123835.62.9268+3305219.76416 neb*
536123841.72.9267+32564719.76218 vS R
537123845.42.9259+3325319.76118 vS R
53812449.32.8448+41384519.67718 vS R N
539124430.52.8431+41381619.67015 vS E60° Spiral?
540124431.82.8425+41414519.67018 vS vR dif
541124436.32.8424+41393119.66918 vS vF R diffic
542124439.02.8418+41415119.66818 vS R diffic
543124446.62.8401+41492619.66617 vS R bM
544124446.92.9440+2619419.66616 vS E60° bM
545124447.52.8417+41235119.66618 vS R bM
546124452.42.8423+41304319.66417 vS R
547124455.42.8398+41463019.66318 vS vF R diffic
548124456.52.8426+41255319.66318 vS R
54912458.42.8376+41544019.65918 vS vF dif D?
550124516.52.8412+41232619.65716 vS E80° bM Spiral?
551124516.92.9453+2550019.65717 vS R bM
552124521.52.8404+4126819.65616 vS R bM
553124527.02.8395+41292119.65418 vS vF E150° bM Spiral on edge
554124528.22.9448+25503819.65418 vS R
555124529.32.9442+26132819.65317 vS E50° bs
556124530.52.9444+26141019.65317 vS R
557124543.22.8361+41441119.64917 vS R N
558124556.52.9436+25491419.64616 vS E40° N

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
559124558.3+2.9436+254813-19.64516 vS E35° N
560154559.12.8368+41291619.64518 vS vF R
561124610.32.8363+41255719.64118 vS vF R bM
562124622.32.8331+4156719.63815 vS E90° bs Spiral?
563124622.82.8358+41221719.63818 vS vF R ◯?
564124626.42.8328+41414319.63717 vS R bM
565124626.62.8335+41353919.63718 vS R bM
566124637.82.8325+4136519.63318 vS R bM
567124646.62.9393+2693619.63116 vS E150° bM
56812475.22.8321+41223119.62518 vS R
569124713.32.8269+41544619.62317 vS R bM
570124714.62.8309+41245219.62217 vS R bM
571124724.32.8272+41463019.62018 vS R bM
572124729.82.8254+4156119.61818 vS R
573124731.62.9395+2545419.61816 vS E10° N
574124738.92.8258+41472019.61518 vS R N
575124743.72.8260+41424819.61418 vS R bM
576124753.52.8245+41481019.61118 vS dif
57712481.62.8256+41342319.60916 vS E125° bM
578124817.52.8252+41273419.60418 vS R
579124825.42.8217+41484019.60218 vS vF R
580124830.92.8246+41233119.60017 vS R N
581124831.32.8206+41531719.60018 vS vF R
582124832.92.8244+41233019.60016 vS R N
583125050.72.9509+22255519.557S R vF
584125115.72.9504+2221019.549vS vF E90°
58513917.42.7068+42335619.13918 vS R
58613924.62.7039+42442119.13514 S E150° four N
58713925.12.7071+4230119.13518 vS R
58813930.52.7093+4218519.13317 vS R bM
58913935.12.7083+42204719.13117 vS R bM
59013936.12.7089+42172819.13017 vS R bM
59113938.62.7084+4219519.12918 vS R bM
59213943.42.7086+42155619.12718 vS R
59313946.82.7056+42281319.12517 vS E120°
59413947.82.7078+4218119.12516 vS E150° bM
59513953.22.7077+42163119.12318 vS R bM
59613953.32.7086+42121919.12318 vS vF R
59713956.22.7042+42284019.12116 vS E90° bM
59813957.32.7028+42363419.12118 vS R
59913101.32.7084+42101319.11914 vS E15° gbM
60013104.62.7015+4240519.11718 vS R
60113105.42.6999+42471219.11716 vS R bM neb*?
60213105.72.7054+42221019.11718 vS R
60313105.82.7061+42184719.11717 vS R bM
60413105.82.7014+42375619.11718 vS R N
60513107.02.7032+42311619.11617 vS E165° gbM
606131011.52.7018+42354519.11418 vS R bM
607131011.72.7030+42304419.11418 vS E50°
608131012.42.7030+4230719.11418 vS R
609131012.82.7009+42394419.11418 vS R
610131014.12.7027+4231819.11318 vS R vF
611131016.22.7027+42301019.11218 vS E70° bM
612131021.02.7057+42143319.11014 neb*
613131022.62.7064+42105219.11018 vS vF R
614131031.32.7009+42322819.10517 vS R bM
615131032.52.6979+42455119.10518 vS R
616131038.22.7026+42221819.10218 vS R bM
617131038.92.7042+42142219.10218 vS R
618131041.22.7033+42175017.10117 vS E150° gbM
619131043.52.7016+42243319.10018 vS E80°
620131047.82.7041+42113919.09818 vS vF R
621131051.42.6951+42511319.09616 vS E75° gbM
622131053.82.6947+4252319.09517 vS E150° bM
623131057.62.7032+42114219.09418 vS R
624131058.12.7007+42225019.09417 vS R bM
62513113.22.7008+42204619.09118 vS R
62613115.92.7011+42175819.09018 vS E30°
62713118.32.7022+42122219.08917 vS R bM
62813119.6+2.7002+422044-19.08818 vS vF R

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
629131115.1+2.7001+42199-19.08618 vS R bM
630131119.72.7017+4210019.08418 vS E35°
631131121.32.6978+42271319.08317 vS E100° bM
632131127.52.6973+4227719.08017 vS E60° gbM
633131129.82.6982+42221819.07918 vS R
634131130.72.6978+42232719.07917 vS E75°
635131136.82.6985+42175819.07617 vS R N
636131138.32.6935+42402119.07518 vS R
637131138.62.6973+42224419.07518 vS E110°
638131140.22.6925+42435819.07518 vS E125°
639131143.02.6960+4227519.07317 vS E130° gbM
640131144.12.6972+42211119.07318 vS R
641131150.02.6933+42364719.07017 vS R bM
642131151.62.6967+42201719.07017 vS R bM
643131153.92.6963+42212419.06818 vS R bM
644131154.92.6964+42204119.06818 vS R bM
645131157.02.6963+4220719.06717 vS E110° gbM
646131158.62.6949+42255419.06618 vS R
647131215.42.6903+42403629.0S918 vS R
648131224.12.6907+42352219.05517 vS R N
649131229.42.6861+42541519.05317 vS E130°
650131237.42.6880+42423819.04916 vS R bM neb*?
651131238.92.6893+42354719.04818 vS R
652131239.72.6862+42494519.04827 vS E45°
653131244.72.6885+42372319.04618 vS R
654131256.62.6872+42383419.04018 vS R
65513134.22.6861+42404619.03718 vS R
656131311.72.6913+42132919.03317 vS R bM
657131311.82.6850+42425619.03318 vS vF dif
658131319.62.6877+42271219.03018 vS E160°
659131321.42.6829+42483619.02918 vS R
660131322.02.6878+42254419.02918 vS R
661131322.82.6837+42443419.02917 vS R N
662131328.22.6825+42474919.02618 vS vF R
663131336.32.6830+4242919.02317 vS R bM
664131357.02.6802+4247419.01418 vS R
66513142.42.6802+42445419.01117 vS R bM
66613235.22.5574+4723818.746vS eeF
667132419.12.5489+47264218.707B pL E80°
66813264.12.5313+47494218.651vS eF
669132615.22.5313+47454718.644S pB l E135°
67013277.82.5273+47415418.616S eeF
671232719.52.5333+47184018.610F S R
672232733.22.5315+47201418.602vS vF E90°
673133134.83.2319-1742318.46816 vS E150°
674133138.83.2351-1722418.46616 vS E150° bM
675133147.93.2332-1793318.46018 vS R
676133152.43.2335-17105218.45818 vS E50°
677133152.53.2339-17124718.45818 vS bn dif
678133254.93.2386-17295718.42217 vS bM E105°
679135742.52.1379+5454517.461B S E90° neb*?
68014150.92.1136+54445017.280S pF bp
6811423.12.1055+54561717.272pB L i
6821508.11.6712+5559214.17018 vS R bM
68315032.41.6694+55582114.14418 vS vF E110°
68415033.71.6634+5645214.14317 vS E160°
6851512.91.6722+55515314.11317 vS R bM
6862514.11.6638+5605814.11117 vS R bM
68715130.42.7322+19405614.082S R F
68815132.32.7225+20111514.080S pF E45°
68925137.22.7251+203114.075vS F E10°
69015231.51.6443+56125314.01816 vS R bM
69115249.22.7273+19495613.999pS F gbM
69215259.61.6345+56204413.98917 vS R bs
69325318.11.6535+55573413.97013 neb*
69415329.02.7243+19562913.958vF S R
69525330.91.6493+5604913.95616 vS N E105°
69615334.92.7213+2053913.952vS F E45°
69715340.92.7207+207713.946vF pL Spiral
69815347.8+1.6564+55515-13.93917 vS E45°

No.α 1900.0Precession.δ 1900.0Precession.Description.
hmss°′″″
69915354.2+1.6479+555940-13.93217 vS bM E135°
69915354.22+1.64792+555940-13.93217 vS bM E135°
70015356.822.72422+19544113.929vS F
70115423.722.72812+19402313.901F pL gbM Spiral?
70215428.222.72482+19502513.896pB S E90°
70315431.921.65632+5546613.89218 vS E35°
70415545.521.62772+56204513.81517 vS R N
70515552.121.64012+5555513.80718 vS R N
70615637.421.62632+56517-13.76018 vS R bM
707222941.022.72142+342253+18.513F S E90°
708223038.122.72992+33583618.544F S R
709223054.822.73062+3402118.552F pS vmbM
71022313.122.73442+33445818.557pB vS m E90° vmbM
711223117.622.73032+3483518.566vF vS m E160°
712223143.922.73342+3413218.579F pL i* inv
71322321.522.73942+33421518.588vF S m E140°
714223229.822.73242+34191318.603pB vS gmbM
715223233.222.73542+346518.605vF pL gbM
716223246.222.73932+33512018.612D* inv set on p*
717223250.322.73472+34135318.614pB S E0° vmbM
71822331.322.74062+34193818.620vB S l E50° vmbM
719223337.722.73612+3421118.640pF pL l E90°
720223350.522.74482+33431618.647Neb*
721223358.122.74102+344918.651vF pS E45°
72222340.622.74422+3349618.652F S E20°
723223410.822.74532+33465918.658F pL gbM
72423829.323.05142+ 403819.543B vS E135°
72523849.623.04992+ 4202619.549vvF S R
72623942.023.05152+ 454319.566B S vE 170°
72723101.123.0529+ 3494219.572B S neb*
728231024.423.05042+ 4212019.580B neb*
729231028.123.05012+ 4251419.581pS vF i
730231111.523.05212+ 451919.594S l E90°
73123474.623.06202+ 7502120.016F pL N Spiral?
732234815.723.06322+ 7353220.021vF BN E100° Spiral
733234939.323.06402+ 7492620.027F vS mbM l E45°
734235613.323.06612+15553420.045vvF vS
735235616.023.06632+15433620.045pB vS
736235636.923.06682+15451220.045F vS
737235640.123.06692+15455920.045F vS E60°
738235652.923.06572+20255720.046S vF F* sp
73923574.823.06762+1549920.046vF pS
74023584.023.06922+15243420.046B m E135° N
741235818.123.06862+2047820.047vS vF E45°
742235853.323.07052+15274820.047F vS
743235920.823.07132+15253220.047vvF vS
744235923.22+3.07102+20940+20.047S F E170°

Abbreviations Used in Description.

The number denotes magnitude,—estimated from the negative.

vS very small, < 30″
S small, 30″ to 2′ or 3′
L large, > 2′ or 3′
B bright
D double
E elongated
F faint
iF irregular figure
M middle or in the middle
N nucleus
R round
b brighter
bn brighter toward the north side
bs brighter toward the south side
bp brighter toward the preceding side
bf brighter toward the following side
bsw brightest toward the south-west
bM brighter toward the middle
dif diffused
diffic difficult
eF extremely faint
g gradually
i irregular
l little
m much
p pretty
pB pretty bright
pF pretty faint
sc scattered
stell stellar
sbM suddenly brighter toward the middle
v very
vbM very much brighter toward the middle
vS very small
F*inv faint star involved
◯ planetary

Positions of Known Nebulæ Determined from the Crossley Negatives.

N.G.C.α 1900.0Precession.δ 1900.0Precession.Remarks.
hmss°′″″
18503327.9+3.2866+47478+19.840
24704211.02.9770-21182119.708
25304238.62.9526-2550419.701
5091189.63.1429+ 8544018.894
51611853.23.1444+ 914618.876
5181193.03.1428+ 8483218.871
52211930.63.1486+ 9281918.857
52411933.03.1414+ 91218.856
52511937.93.1464+ 9105418.854
5321202.53.1430+ 8443518.841
...1217.33.1493+ 9232118.810N. G. C. Sup. 114
62813124.83.2141+15162218.473
89121617.73.7447+41534416.609
90621859.53.7502+41381016.476
10232348.13.7387+38374215.681
105523637.53.0739+ 004815.545
106823733.73.0658- 0262315.493
107223823.73.0715- 07815.447
10842414.52.9513- 7595615.300
163843633.43.0287- 2067.139
193152448.73.9695+34107+ 3.067
236671819.36.4249+692451- 6.718
2371-271916.43.7891+2941136.797
240372711.75.8367+6549137.445
262483224.23.4566+2042412.370
268384627.63.7417+33475113.317
28419157.84.1755+5124315.080
2903, 592630.43.4065+21561515.716N. G. C. 2903 and 2905
300394239.13.5786+3353916.553
30219451.03.5735+3411416.670
303194717.95.0430+69321416.785
307995511.44.1050+5693417.147
311510015.12.9877- 714617.372
315610730.53.1107+ 3372917.680
316610834.93.1143+ 3551117.724
31691094.23.1154+ 3574117.744
3184101217.43.6158+41552717.874
3198101347.93.6919+463317.933
322210176.53.2879+20233018.062
3227101759.13.2864+20241418.094
322610182.83.2859+20221318.097
...102055.24.5248+68551418.204Coddington’s Neb. in Ursa Major.
355611536.83.5420+5613019.485
35871190.13.5029+55334719.553
3623111342.83.1374+13382319.639
362711152.23.1352+13321819.662
3726112755.43.2764+47345019.851
4226121128.22.9995+47345320.024
4231121151.12.9956+4804620.022
4232121151.22.9957+47593920.022
4244121229.43.0148+38243420.017
4248121253.12.9890+47575220.016
4254121345.03.0509+14581920.011
425812140.82.9821+47513520.010
4292121610.33.0639+ 59119.997
4303121648.73.0637+ 514219.993
4321121751.03.0418+16223619.986
4379122011.23.0382+1694319.970
4382122021.33.0321+18444519.968
4394122053.03.0310+1846719.964
4501122656.63.0304+14582119.909
451612285.13.0282+1573819.898
452712292.23.0629+ 3121919.886
4533122915.63.0638+ 2523919.884
4536122920.63.0642+ 2442219.883
4565123123.32.9812+26322019.859
462712377.32.9316+3372219.784
4631123714.4+2.9315+33519-19.783
4712124440.3+2.9475+26055-19.667
4725124533.02.9434+2624419.652
4736124610.52.8344+41395419.641
4747124652.42.9381+2619819.629
4826125149.12.9499+22133019.538
5055131120.52.6965+42332819.083
5194132540.12.5358+47424318.663
5247133238.63.2368-17222818.431
5457135940.42.1264+54494417.375
585715254.82.7244+19585613.993
58591532.22.7245+1958113.986
586615345.31.6405+5685413.941
587015348.51.6556+555150-13.938
7315223053.42.7270+34178+18.552
7331223224.52.7374+33535518.600
7333223240.12.7380+33554418.609
7336223242.62.7377+33574718.610
734022334.72.7399+33532818.622
753723929.33.0521+ 3571419.562
754123938.73.0520+ 3592119.565
7778234812.93.0635+ 7185520.021
7779234820.03.0636+ 7191220.021
7780234825.53.0633+ 7334420.021
7781234839.23.0638+ 7181720.022
7782234847.13.0638+ 7245220.023
781423587.53.0693+15352020.046
7817235851.23.0699+20114620.047