ON THE ALLEGED OBSERVATION OF A LUNAR ECLIPSE BY BERING IN 1728-9.

Bering was in Eastern Siberia, Kamchatka and the adjacent waters in 1728 and 1729. Could he have observed a lunar eclipse there at that time?

According to the ephemeris of Manfred¹ published at Bonn in 1725 there were two partial eclipses of the moon visible in Europe in 1728, and two total eclipses of the moon in 1729.

¹ Manfredius (Eustachius). Novissimae ephemerides motuum coelestium e Cassinianis tabulis ad meridianum Bononiae supputatae auctoribus Eustachio Manfredio (etc.) Tomus 1. ex anno 1726 in annum 1737 (etc.) 4° Bononiae, MDCCXXV.

In regard to these four eclipses the ephemeris furnishes the following data:


	1728, Feb. 24.	1728, Aug. 19.	1729, Feb. 13.	1729, Aug. 8.

Eclipse begins	18^h 32^m	4^h 07^m	7^h 45^m	12^h 02^m
Total immersion	— —	— —	8 46	13 02
Middle of eclipse	20 0	5 35	9 35	13 52
Emersion begins	— —	— —	10 24	14 42
Eclipse ends	21 29	7 03	11 25	15 42

Digits eclipsed	9 51 S.	7 45 N.	19 46	19 44 S.
Sun rises	18 36	— —	— —	— —
Sun sets	— —	6 49	— —	— —
Eclipse	Partial	Partial	Total	Total.

Sun's declination	–9° 38'	+12° 42'	–13° 16'	+16° 09'
" hourly motion	+ 0.9	– 0.8	+ 0.8	– 0.7

In this table the calendar is Gregorian, the time is apparent or true sun time, the day is reckoned from noon and the hours are counted continuously through the entire 24.

The present observatory in Bonn is in

Latitude	50° 43' 45"	N.
Longitude	0^h 28^m 23^s	E. from Greenwich.

At the date of the first eclipse Bering was on his way across the southern end of Kamchatka from Bolsheretsk to Lower Kamchatka. This would make his position somewhere near latitude 55° N. and longitude 160° or 10^h 40^m E. from Greenwich.

He was therefore 10^h 12^m east of Bonn for which we have the elements of this eclipse as computed by Manfred. With this data together with the latitude and sun's declination we have the following data for the eclipse in the region where Bering was.

Beginning of eclipse	4^h 44^m
Middle of eclipse	6 12
End of eclipse	7 41
Sun sets	5 07

This means that the sun set, bearing about W. by S. ½ S., and the moon rose in partial eclipse, bearing about E. by N. ½ N., at 5^h 07^m after apparent noon or 23 minutes after the eclipse had begun. The eclipse lasted for 2^h 34^m after sunset, or until 7^h 41^m in the evening, thus rendering observation of the last contact plainly visible.

At the date of the second eclipse of 1728, August 19, Bering was at sea somewhere in the vicinity of the strait which bears his name. Assuming his position to have been latitude 65° N. and longitude 188° or 12^h 32^m E. from Greenwich, equal to 12^h 04^m E. from Bonn, and as before taking the data from Manfred's ephemeris we have as follows:

Beginning of eclipse	16^h 11^m
Middle of eclipse	17 39
End of eclipse	19 07
Sun rises	16 04

It thus appears that the first contact of this partial eclipse of the northern limb of the moon may have been just barely visible to Bering. The moon bearing about SW. by W. was entering the earth's shadow about five minutes before the sun's rising and its own setting. If much importance attaches to determining the possibility to Bering of observing this eclipse then a more precise calculation is needful.

At the date of the first lunar eclipse of 1729, February 13, Bering was at Lower Kamchatka, in latitude 56° 03' N. and longitude 162° 15' or 10^h 49^m E. from Greenwich equal to 10^h 21^m E. from Bonn. For this place we have from Manfred:

Eclipse begins	18^h 06^m
Total immersion	19 07
Middle of eclipse	19 56
Emersion begins	20 45
Eclipse ends	21 46

Sun rises	19^h 21^m

Thus it appears that this total and almost central eclipse of the moon lasting 3^h 40^m began at Bering's station 1^h and 15^m before sunrise of February 14, the total immersion occurring 14 minutes before sunrise. It is manifest, therefore, that Bering might have observed this eclipse.

The second lunar eclipse of 1729 occurred August 8, when Bering was in or near Okhotsk and about returning to Europe. We may assume his position to have been latitude 59° 20' N. and longitude 142° 40' or 9^h 31^m E. from Greenwich, equal to 9^h 03^m E. from Bonn. This eclipse was also total and almost central, but at Bering's station was wholly invisible, beginning at 9^h 05^m A.M. and ending at 12^h 45^m P.M.