...

[p. 164-165] M. Messier once more profited from the clear weather on the 28th [of August, 1758] in the morning for observing smaller star which he had not noted on the preceding days, & which are found neither in the catalog nor in the celestial charts of Flamstead; nevertheless, he compared them [their position] with the comet in a manner which I'm going to report.

What would be more remarkable in that night, was that when he went through the sky with the catadioptric telescope into the surroundings of the southern horn of Taurus, marked Zeta by Bayer, (*) M. Messier discovered there a light almost resembling that of the Comet, but which was even more vivid, whiter & a bit more elongated than the Comet he observed at that time: That comet had appeared to him always almost round in its coma, without an appearance of either a tail or a beard. When the discovery of this new light or nebulous star didn't come to an end of the observations of that morning session, before the sky covered, M. Messier didn't have the time to determine its exact situation with respect to the neighboring stars of the southern horn of Taurus: there will be reported the details of observations, & there will be marked the precise position of that new nebula, its magnitude & the degree of its light compared to that of the Comet of 1758, so that those who have not been able to find that new Comet with the refractors which have been employed to find it, will be able to judge by the impression of that nebula what they could hear to be prevented, supposed that that nebula does not change its state of magnitude.

---

(*) [Marginal Note:] Discovery of a new nebula.

...

[p. 169-170] M. Messier also determined that night the situation of the Comet with regard to the neighboring stars, & the situation of these stars with regard to each other, what he did principally from the beginning of dawn, in order to better perceive the wires of the micrometer, before the light of the new day became too strong to make the stars & the nucleus of the Comet disappear; he also has determined exactly on [September] 10 in the morning the position of the nebula, which he had commenced to perceive on August 28 in the morning near the southern horn of Taurus.

The observations lasted until 4h 1/2 in the morning, when the force of the dawn made the comet disappear.

The night of September 10 to 11 was also suited for observations as the preceding, the Comet appeared from midnight of the 10th, & the same phenomena were observed as the night before, so that it is unnecessary to report them again.

The night of [September] 11 to 12, the sky was rather serene to allow viewing the Comet from midnight to 4h 1/2 on the 12th in the morning; but it didn't appear as distinguished as the two preceding days; despite the sky was rather serene, it was difficult to distinguish the nucleus; having compared the appearance or the light of the Comet with that of the nebula of the southern horn of Taurus (**), one finds there well a difference, the light of the nebula was considerably stronger in this morning than that of the Comet; instead of, like the two preceding days, when the two lights were approaching equality to each other, that of the Comet was always fainter, what will serve to make known that in summer the light of the present Comet to those who want to observe that nebula with good refractors or [reflecting] telescopes, supposed that that nebula always conserves the same degree of light.

It is unnecessary to say that one has also profited in this morning from the good weather to determine the situaion of the Comet & the stars with repect to each other.

---

(**) [Marginal Note:] Difference of the appearances of the Comet & the new nebula.

...

On p. 188, the position of the "new nebula" is given as follows:
Nebulous star discovered on August 28, 1758: Observed Right Ascension: 80d 0' 33" (5h 20m 02s), observed Northern Declination: 21d 45' 27"; observed [ecliptical] Longitude: Gemini 20d 43' 30" (80d 43' 30"), observed Latitude: South 1d 23' 28".

References

• Joseph Nicholas Delisle, 1759. Mémoire sur la comète de 1758 [Memoir on the comet of 1758]. Par M. de l'Isle. Read November 15, 1759. Mémoires de l'Academie Royale, 1759. P. 154-188.
  Felice Stoppa's webpage on this memoir and map

Last Modification: February 4, 2007