The employment of writing down the observations when my brother uses the twenty-foot reflector does not often allow me time to look at the heavens, but as he is now on a visit to Germany, I have taken the opportunity to sweep in the neighbourhood of the sun in search of comets; and last night, the 1st of August, about 10 o’clock, I found an object very much resembling in colour and brightness the 27 nebula of the Connoissance des Temps, with the difference, however, of being round. I suspected it to be a comet; but a haziness coming on, it was not possible to satisfy myself as to its motion till this evening. I made several drawings of the stars in the field of view with it, and have enclosed a copy of them, with my observations annexed, that you may compare them together.
August 1, 1786, 9h 50ʹ. Fig. 1. The object in the centre is like a star out of focus, while the rest are perfectly distinct, and I suspect it to be a comet.
10h 33ʹ. Fig. 2. The suspected comet makes now a perfect isosceles triangle with the two stars a and b.
11h 8ʹ. I think the situation of the comet is now as in Fig. 3, but it is so hazy that I cannot sufficiently see the small star b to be assured of the motion.
By the naked eye the comet is between the 54 and 53 Ursæ Majoris and the 14, 15, and 16 Comæ Berenices, and makes an obtuse triangle with them, the vertex of which is turned towards the south.
Aug. 2nd, 10h 9ʹ. The comet is now, with respect to the stars a and b, situated as in Fig. 4, therefore the motion since last night is evident.
10h 30ʹ. Another considerable star, c, may be taken into the field with it by placing a in the centre, when the comet and the other star will both appear in the circumference, as in Fig. 5.
These observations were made with a Newtonian sweeper of 27-inch focal length, and a power of about 20. The field of view is 2° 12ʹ. I cannot find the stars a or c in any catalogue, but suppose they may easily be traced in the heavens, whence the situation of the comet, as it was last night at 10h 33ʹ, may be pretty nearly ascertained.
You will do me the favour of communicating these observations to my brother’s astronomical friends.
I have the honour to be,