Histoire Céleste Française

[Demonperformer]

Probably a bit of a long-shot, but is anyone familiar with the 1801 Histoire Céleste Française by Jerome Lalande (https://archive.org/details/histoireclestef00lalagoog)? Specifically with the way in which the declination readings are recorded? I attach the image of a sample page, which may help explain my problem.

On the right hand column, there are three stars labelled 15, 16 & 17 "Chiens" (=CVn), each of which has a "distances au zenit" (=NPD) of between 9 & 10  degrees, which my understanding would give them a declination of between +80 & +81 ... which is clearly wrong.

Now I know I could just look up the declinations in my modern star list, but my situation is slightly more problematical. I have been referred to a star that "is the star observed by Lalande in Histoire Celeste page 58, at 12h 40m 23,2s, mag.6" (near the bottom of the left hand column). Now, if I can find the declination, I can precess it to J2000 and identify exactly to which star this refers, but without a declination, I am unable to do so.

Now, it is true that there is a massive introduction to the volume, which may contain the answer, but it is in French - and mine is just not up to the task.

So can anyone offer any info on how these (to me) weird NPD readings relate to reality?

Thanks.

[Not totally sure this is the right forum -- should it be in astrolounge? -- happy for mods to move it if they think it is better suited elsewhere]

hcf84.pdf

[Demonperformer]

Re-reading post, I think I see the solution. The zenith is not the pole, so I am going to have to work it out from the latitude of the observatory. I guess that makes sense in light of the instrument being used.

This might take some time ...

[Demonperformer]

Well, it was a bit fiddly, but it gave me an unambiguous solution. For anyone interested, the "star observed by Lalande in Histoire Celeste page 58, at 12h 40m 23,2s, mag.6" is HD111604.

Thanks.

[markse68]

Does it have significance? Says it’s variable

Mark

[Demonperformer]

11 hours ago, markse68 said:

Does it have significance? Says it’s variable

Mark

I guess not in the grand scheme of things.

My interest lies in the fact that it is one of the 458 stars that were observed, measured and recorded by Flamsteed that failed to be included in the 1725 Catalogus Britannicus, and which is not specifically identified as such in the British Astronomical Catalogue, so it requires a bit more searching to identify what they are exactly. This is my first time dealing with the Histoire Céleste Française and it is the first time I have encountered this method of recording declination and was confusing it with NPD. It was only about five minutes after my original post that I realised that error and would have just deleted the post, but could not find a means of doing so, so updated it with my ongoing thinking. I just included the identification to round things off - I get rather irritated by threads that leave you hanging (I found the answer, but I'm not going to tell you what it is!).

Thanks.