Use almstars catalogues to improve Almagest sky culture

[abalkin]

Catalogues

1. Toomer/Grasshoff (cat1.dat)
   Data for this catalog was transcribed from Appendix B of Grasshoff's The
   History of Ptolemy's Star Catalog (Springer-Verlag, 1990). With minor
   variations, this is based on Toomer's translation of the Almagest, first
   edition (Duckworth, 1984). The transcriptions were reconciled with the
   second edition of Toomer (Princeton University Press, 1998), which is
   also the source of the star descriptions.

2. Peters/Knobel (cat2.dat)
   Transcribed from Peters and Knobel, Ptolemy's Catalogue of Stars
   (Carnegie Institution, 1915).

3. Manitius (cat3.dat)
   Initially CDS V/61, the electronic catalog by Jaschek, but substantially
   corrected by consulting the source, Manitius's 1913 German translation
   of the Almagest, the (Teubner, 1962) edition with the forward by
   Neugebauer. The star descriptions, not present in V/61, were transcribed
   directly from Manitius.

4. Pickering (catpick.dat)

See http://www.etwright.org/astro/almagest.html#cat

Description

Fixes #1646

Screenshots (if appropriate):

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• This change requires a documentation update

How Has This Been Tested?

Test Configuration:

• Operating system: <Name, version number>
• Graphics Card: <Manufacturer (likely Intel, NVidia, AMD?), Model (HD, Geforce, Radeon..., with model number), driver version?>

Checklist:

• My code follows the code style of this project.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching skycultures/**:

• Did you remember to update po/stellarium-skycultures/POFILES.in and src/translations.h files respectively to changes in sky cultures?
• Did you remember to define classification parameter in sky cultures?

This is an automatically generated QA checklist based on modified files

[github-actions]

Thanks for adding your first pull request to Stellarium. If you have questions, please do not hesitate to contact us.

[lgtm-com]

This pull request introduces 2 alerts when merging ddd634d into edf0183 - view on LGTM.com

new alerts:

• 1 for Unused local variable
• 1 for Unguarded next in generator

[lgtm-com]

This pull request introduces 1 alert when merging 321e2b5 into 915a107 - view on LGTM.com

new alerts:

• 1 for Unused local variable

[abalkin]

@sushoff, @alex-w - I have removed the "draft" status from this PR because I believe it is already an improvement. If this is acceptable in principle, I would like to update the culture description to give proper credit to Ernie Write, but this can be done in a separate PR.

[gzotti]

The PR is flagged as "needs change in documentation". What exactly has changed in the documentation?

I see additions of source catalogs (are they OK to distribute via FOSS or do they have their own licenses?) and some Python tools that probably extract the star names from the respective catalogs. What does the user do with this? Are the tools geared towards the ordinary user (who will have to run them as superuser/Administrator as the skycultures goes in protected install directories; this must be documented in the Skycultures chapter of the User Guide) or are the tools for the developers of this SC, and the result is delivered to the end users (This must be documented in a README.md here)?

I don't talk bad about this effort, I think it's valuable work, but it must become clearer what we are adding here and why. As said before, this may also be seen as starting point for the "user star list" plugin, providing some catalogs and sample code.

[alex-w]

The PR is flagged as "needs change in documentation". What exactly has changed in the documentation?

This flag was put by me, because proposed changes at least require updating description of SC and list of sources. But okay, I’ve removed this flag now.

[abalkin]

What exactly has changed in the documentation?

I have not made any changes to the documentation yet, but as I indicated, some changes should be made to the culture description to acknowledge the use of third party works.

are they OK to distribute via FOSS or do they have their own licenses?

The "almstars" software and the associated data files that I copied have been published under GNU Public License, version 2 which is the same as Stellarium's own license.

some Python tools that probably extract the star names from the respective catalogs. What does the user do with this?

The python tool was written by me and I am happy to contribute it. At the moment, it mostly serves as a documentation of how star descriptions were extracted and linked to HIP numbers. In the future, this script may be incorporated into the build system to maintain a single source of star names.

(This must be documented in a README.md here)

Good idea. There is currently no such file in skycultures/almagest directory, but technical details about the make_names.py script do not belong to the user facing description file.

it must become clearer what we are adding here and why

My goal here is simply to make all 1028 descriptions from the Almagest to be accessible in Stellarium. The current behavior when Almagest is selected as the starlore is to display the descriptions of very few stars.

Most stars get no descriptions at all, including those in the major constellations

[abalkin]

I switched back to draft because we should be consistent with the Al-Sufi skylore and turn long descriptions into "additional" rather than primary names.

[abalkin]

@gzotti - did I address all your comments?

[sushoff]

I switched back to draft because we should be consistent with the Al-Sufi skylore and turn long descriptions into "additional" rather than primary names.

Don't think so! 1. We should not do it consistent with XY because we want to show historical development. 2. I want the primary name to be the original one.

[abalkin]

1. We should not do it consistent with XY because we want to show historical development.

@sushoff - al-Sufi in the context of Almagest is not just "XY", it is a very closely related culture. In fact, @kajaji, the author of the Al-Sufi culture implementation used the same Ernie Wright's files to obtain English translations as I do here. "The translation of star descriptions from Arabic into English was extracted from Ernie Wright website[6] which was transcribed from Toomer's translation of the Almagest[7]." (See skycultures/al-sufi/description.en.utf8). The "Con n" (or "Con_n") abbreviations do not come from historical sources. Ernie Wright added IAU-style abbreviations to his tables in order to preserve the groupings of stars by constellations. The ordinal numbers within constellations are also not present in Almagest and the Book of Fixed Stars uses abjad numerals.

2. I want the primary name to be the original one.

With very few exceptions, there is no such thing as a name of a star in Almagest. I was able to find 11 proper names in Toomer: Arcturus (α Boo), Lyra (α Lyra), Capella (α Aur), Aquila (α Aql), Praesepe (M 44), Regulus (α Leo), Spica (α Vir), Vindemiatrix (ε Vir), Antares (α Sco), "the Dog" (Sirius, α CMa) and Procyon (α CMi). Ptolemy's descriptions are not suitable for primary names for at least two reasons: (1) they are too long (e.g. "The most advanced of the 3 stars on the spine in the back, following [i.e. to the rear of] the star on the elbow of Andromeda") and (2) they often refer to a previously defined group (e.g. there are 18 stars described as "The middle one of these"). Note that I don't have a solution for the second issue yet, but the most likely solution is to repeat the definition of the group in each description. For example, ꭓ Oph can be described as "The middle one of [the 3 stars in a straight line in the left lower leg]". This, however will lengthen the already long descriptions make the first issue worse.

Overall, I find the use of invented abbreviations to be the only practical solution if we want to provide complete Almagest-like sky cultures. Think of "Con n" labels as a kind of footnote marker inviting the user to click to see a longer description. I'll be happy to entertain alternatives as long as they are reasonably short and can be systematically applied to all stars in the catalogue.

[sushoff]

Ptolemy's descriptions are not suitable for primary names for at least two reasons: (1) they are too long

yes, I agree

but in as-Sufi they are used anyway: I am still translating this catalogue for Stellarium

[abalkin]

but in as-Sufi they are used anyway: I am still translating this catalogue for Stellarium

@sushoff - which version of Stellarium are you looking at? With the latest master, I see the following when al-Sufi skylore is selected:

As you can see, the display is similar to what I implemented for Almagest. (See my note in #1646. )

English translations of secondary names do seem to be incomplete, but they are not used as star labels – only as additional names.

[abalkin]

I am still translating this catalogue for Stellarium

@sushoff - have you seen Hafez, Ihsan (2010) translation of sections of Al-Ṣūfī's 'Book of the Fixed Stars'? It appears that the author placed that work in the public domain and there should be no issues with copying the names of the stars from there. To give you a flavor, here is a discussion of the seven UMi stars:

As for the Small (Bear), the Arabs call the seven (stars) of the group Banāt Na’sh al-Ṣugrha (The Little Daughters of the Bier or Coffin). The four on the rectangle are the Na’sh (bier or coffin) and the three on the tail are the Banāt (the daughters). (The Arabs) call the two brightest stars of the rectangle al- Farqadain and the bright star on the end of the tail al-Juday; this (star) is used to locate the Kiblah (= the direction of Makkah).
The three stars on the tail, together with the fourth and sixth (the word “seventh” has been scratched out) form a curved line. Next to the brightest (star) of the al-Farqadain, which is the sixth, is a fainter star, on the same line as the al-Farqadain (but) not of the constellation. -- Hafez, Ihsan (2010), page 112.

[sushoff]

sorry, I mean, I am translating the (new) SC from English to German (sorry, did not make it completely for the last release: only roughly 50% was done those days)

[kajaji]

I am still translating this catalogue for Stellarium

@sushoff - have you seen Hafez, Ihsan (2010) translation of sections of Al-Ṣūfī's 'Book of the Fixed Stars'? It appears that the author placed that work in the public domain and there should be no issues with copying the names of the stars from there. To give you a flavor, here is a discussion of the seven UMi stars:

As for the Small (Bear), the Arabs call the seven (stars) of the group Banāt Na’sh al-Ṣugrha (The Little Daughters of the Bier or Coffin). The four on the rectangle are the Na’sh (bier or coffin) and the three on the tail are the Banāt (the daughters). (The Arabs) call the two brightest stars of the rectangle al- Farqadain and the bright star on the end of the tail al-Juday; this (star) is used to locate the Kiblah (= the direction of Makkah).
The three stars on the tail, together with the fourth and sixth (the word “seventh” has been scratched out) form a curved line. Next to the brightest (star) of the al-Farqadain, which is the sixth, is a fainter star, on the same line as the al-Farqadain (but) not of the constellation. -- Hafez, Ihsan (2010), page 112.

@abalkin @sushoff The [Arabic] names of the stars are already present in Al-Sufi SC, either as another secondary name after the long description or as an asterism name if they are a group of stars.

[abalkin]

Why not just add an asterisk to the designation? In any way the designation "con n" or "Con n*" should be described in the description.en.utf8 file.

@alex-w - I added a paragraph to the description file describing the "Con n" designations. (See 5d19165.) I still like lowercase more than adding an asterisk because "outside of the figure" stars tend to be fainter and less important. A notable exception is Arcturus, but it has a proper name, so users will only see "boo 23" if they click on "Arcturus". In any case, this is something that can be easily changed in the future after we reach a consensus on how this should be done across Almagest-like sky cultures.

[abalkin]

This list of objects was removed from dso_names.fab file: M 45, Mel 25, Mel 111, NGC 6441, Mel 180.

Why?

@alex-w - a short and honest answer is because these entries did not appear in the Write's table. I can easily add those back, but I am not sure that would be historically accurate. Let's consider the cases of M 45 (Pleiades) and Mel 25 (Hyades). Unlike astronomers of telescope era, Ptolemy did not identify Pleiades or Hyades as star clusters. For him, those were just asterisms.

Copying from Toomer,

30-33 The Pleiades:
30                  the northern end of the advance side
31                   the southern end of the advance side
32                  the rearmost and narrowest end of the Pleiades
33                  the small star outside' the Pleiades, towards the north

11-15 The stars in the face, called ‘the Hyades’:
11                 the one on the nostrils
12                 the one between this and the northern eye
13                 the one between it [no. 11] and the southern eye
14                 the bright star of the Hyades, the reddish one on the southern eye
15                 the remaining one, on the northern eye

So, I don't think it is correct to identify Ptolemy's Pleiades and Hyades with M 45 and Mel 25 open clusters. Instead, these should be listed as asterisms. This said, changing the treatment of these objects is outside of the scope of this PR and I can easily restore the existing associations pending future developments. Please let me know how you would like to proceed.

[abalkin]

This list of objects was removed from dso_names.fab file: [...], Mel 111, NGC 6441, Mel 180.

For completeness, let me address the rest of the deleted DSO names. The last two entries refer to the same cluster and I think in this case we should at most keep the NGC association with the Almagest description.

Mel 111 (Coma Star Cluster)

A strong case can be made for keeping this. In Toomer, we find a mention of Coma in the description of Leo 33

33    The northernmost part of the nebulous mass between the edges of Leo
      and Ursa |Major|, called Coma [Berenices]

and in the summary of stars "around Leo outside the constellation":

"5 stars, 1 of the fourth magnitude, 4 of the fifth, plus Coma" (page 368.)

Mel 180, NGC 6441 (globular cluster in Scorpius)

22    The nebulous star lo the rear of the sting

This PR associates "sco 22" with G Sco, which is correct, but Toomer also says the following in the footnote:

"Manitius identifies this as ('G Scorpii, P-K as gamma Telescopii, an obsolete designation which is the same as G Scorpii (BSC 6630). But the description ‘nebulous’ obviously includes the globular cluster (cf. P -K no. 567 p. 105 and Burnham III 1689)."

So, I am inclined to restore the "NGC 6441" association, but I think "Mel 180" is strictly redundant.

[abalkin]

I did not hear back from @alex-w, so in eeb1d1c, I conservatively restored the DSO names including Pleiades and Hyades.

[sushoff]

Ptolemy did not identify Pleiades or Hyades as star clusters. For him, those were just asterisms.

well this is only half of the truth! Of course, these clusters were considered as star clusters - but the concept of star clusters was different those days.As stars were not considered as bodies in space with an evolution, they did not consider a group of gas balls in space but a grouping of dots on the celestial globe.

Indeed this view of the abovementioned clusters (Pleiads, Hyades, Com, Perseus...) had been given since >2000 years at this time. Ptolemy in particular wrote a star catalogue! He needed points in the mathematical sense to address with point-coordinates - the concept of areas on a curved plain was not yet developed, he did not have a mathematics to describe it.

The concept of star clusters did not fit into a star catalogue. The Pleiades were considered as "seven sisters" but he lists only 4 stars because this way, the area was clearly defined. He does not aim to list all stars that are seen on the sky but he aimed to define the positions of the constellation areas.

Therefore, I don't consider it wrong to delete these clusters. I labeled the clusters as a total because they were already named as a group in antiquity - no matter whether or not Ptolemy listed some single star members in his catalogue. I think, the label "M45" for a modern hobby astronomer designates the same as "Pleiades" for Ptolemy, Hipparchus, Ovid, Hyginus, Aratos ... and all the others.

[alex-w]

@sushoff is this PR ready for merging by your opinion?

[sushoff]

there is an important diacritical sign missing at the beginning of Ὑάδες

[alex-w]

Thanks for fix @abalkin

Please reiview the changes @sushoff

[sushoff]

Thanks for fix @abalkin

Please reiview the changes @sushoff

yes, for the moment, it's ok, I think

[alex-w]

@sushoff OK, thanks! Can I merge it now?

[sushoff]

please do so

[github-actions]

Hello @abalkin! Please check the fresh version (development snapshot) of Stellarium:
https://github.com/Stellarium/stellarium-data/releases/tag/weekly-snapshot

[github-actions]

Hello @abalkin! Please check the latest stable version of Stellarium:
https://github.com/Stellarium/stellarium/releases/latest