Talk:Almagest

Dear colleagues,
I am leaving the present message out of courtesy to other editors watching this article.
I recently noticed that, in the section headed Books, the entry for Books VII and VIII is not displayed to the reader, even though the wikitext source is present to editors, in edit mode. I have now determined that the problem is caused by the presence of the following paragraphs, especially including the blank lines which I have replaced by 2x "<br />" each, in the wikitext quoted below:

(The catalogue actually contained 1,028 entries, but three of these were deliberate duplicates, because Ptolemy regarded certain stars as being shared between adjacent constellations. Three other entries were non-stellar, i.e. the Double Cluster in Perseus, M44 (Praesepe) in Cancer, and the globular cluster Omega Centauri.)^[1]

Ptolemy states that the longitudes (which increase due to precession) are for the beginning of the reign of Antoninus Pius (138 AD), whereas the latitudes do not change with time. (But see below, under The star catalog.) The constellations north of the zodiac and the northern zodiac constellations (Aries through Virgo) are in the table at the end of Book VII, while the rest are in the table at the beginning of Book VIII. The brightest stars were marked first magnitude (m = 1), while the faintest visible to the naked eye were sixth magnitude (m = 6). Each numerical magnitude was considered twice the brightness of the following one, which is a logarithmic scale. (The ratio was subjective as no photodetectors existed.) This system is believed to have originated with Hipparchus. The stellar positions too are of Hipparchan origin, despite Ptolemy's claim to the contrary.

Ptolemy identified 48 constellations: The 12 of the zodiac, 21 to the north of the zodiac, and 15 to the south.^[2]

In order to verify the cause of this problem, I created a sandbox version of the present article, in which you can trace my tests in 'View history', as usual. I will now proceed with relocating the above paragraphs and their citations into a new 'Notes' section. In addition, I am proposing to consolidate all citations in a consistent style, similar to the approach taken in the articles on Australasian Antarctic Expedition or Jack Whiting (actor), for example.
I would therefore welcome the views and suggestions of other editors, and will implement these changes into my sandbox before carrying them over into the present article in mainspace, unless anyone proposes another solution. Thank you.
With kind regards;
Patrick. ツ Pdebee.^{(talk)(become old-fashioned!)} 12:52, 7 April 2023 (UTC)
PS: I have also ordered Ridpath's book, to determine the page numbers relevant to the cited text and create {{cite book}} templates, since these page numbers are missing from the web version of this book.

Dear colleagues,
As an update to the above, I have now been able to elucidate the cause of the above problem: the {{unordered list}} template was preventing the entry for Books VII and VIII from being displayed to the reader because the prose at that entry contained equal signs ("="), such as in ({{mvar|m}} = 1), for example. To fix the problem (and also overhaul the referencing method), I successfully applied the following changes in my sandbox copy of the article, and also to its original version in mainspace:

1. renamed the Books section to The Syntaxis Mathematica books, to differentiate it from the new 'Books' subsection in the restructured 'References' section. (see point 5. below);  Done

2. removed the {{unordered list}} template and added a bullet in front of each Book entry;  Done

3. inserted the extra prose (causing the issue in Books VII and VIII) into an 'explanatory note' using a {{refn}} template with a group name of group=note, making sure to precede the content of that note with a numbered parameter to address the issue introduced by the '=' signs, as explained here;  Done

4. converted the <ref>...</ref> tags to {{sfn}} templates for Ridpath's book (1998), linked to a {{cite book}} template relocated into a new 'Books' subsection in the new 'Citations' section;  Done

5. I have also restructured the 'References' section and subsections (including a new 'Further reading' section for those listed books not used as references), all in order to adopt the good practices used in Australasian Antarctic Expedition, a featured article.  Done

6. All that's left to do is to relocate all citation templates from the body of the article into the new 'Sources' subsections, and replace all <ref>...</ref> tags with {{sfn}} templates, which will only take me a few hours.  Done (See all diffs.)

I will now apply the remaining changes (point 6.) in the near future, and will update its status on completion. Should other editors disagree with any or all these changes, then please let me know, or simply revert them. Thank you.
With kind regards;
Patrick. ツ Pdebee.^{(talk)(become old-fashioned!)} 15:57, 8 April 2023 (UTC)

Final update: all completed today!
Patrick. ツ Pdebee.^{(talk)(become old-fashioned!)} 17:48, 13 April 2023 (UTC)

The name section doesn't cite a single source. This should either be removed or sources added. 76.186.217.39 (talk) 21:17, 30 June 2023 (UTC)

Should we put in this map in the section about the star catalog? Eric Kvaalen (talk) 10:02, 18 February 2024‎ (UTC)

No, I don't think it's relevant to the subject. And unsourced. Skeptic2 (talk) 17:31, 18 February 2024 (UTC)

It's tangentially relevant, but it doesn't seem necessary to me, and this diagram is very wide. –jacobolus (t) 21:09, 18 February 2024 (UTC)

There's another good reason to put it. The longitudes in the Almagest are generally about 1° too low. The best explanation is that Ptolemy was actually reproducing the catalog of Hipparchus, and he added 2 and 2/3 degrees to Hipparhus' longitudes because he thought the precession over the 265 years since Hipparchus was that much, but it was actually 3.7°, so he was off by 1°. In that case, it's interesting to know whether his zodiac constellations fit into their respective longitude ranges, because if Hipparchus put all the stars (near the ecliptic) between, say, 0° and 30° (at his time) into Aries, and then Ptolemy added ${\displaystyle 2{\tfrac {2}{3}}}$ degrees to them all, then in the Almagest they will be between ${\displaystyle 2{\tfrac {2}{3}}}$ and ${\displaystyle 32{\tfrac {2}{3}}}$ degrees in longitude. This map allows one to see whether that is the case (more or less).

Also, it shows the boundaries of the constellations. I think it's a very interesting map, and I don't see why if you don't like it you should deprive other people of looking at it. This is the best place for it, after all.

As for it being unsourced, well, the source is the Almagest star catalog. 15:51, 3 September 2025 (UTC)

It is sourced on the WikiMedia site but it is clearly clipped from a larger map as you can see parts of constellation names at the top and the bottom of the image. Nor is it clear if the "constellation boundaries" include the so-called "unformed" stars in each constellation which are not part of the figure but which Ptolemy catalogued as well. AstroLynx (talk) 17:58, 3 September 2025 (UTC)

There were no boundaries to Ptolemy's constellations, so the diagram is misleading. Skeptic2 (talk) 09:19, 4 September 2025 (UTC)