Allow elongation dependent cultural names

[gzotti]

Name the Morning Star and Evening Star only if visible as such.

Description

This little branch provides an extension of the CulturalName, introducing the first "special" constants. More might come as needed.

The index.json NAME entry for planets can now be extended with an "elongation" tag which can be eastern or western.
In gthe code, this is translated to the Special constants Morning or Evening. I am not sure this is meaningful, maybe they should bear equal names. But also not sure which of the two is the better. opinions?

Fixes #4326

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
• Housekeeping

How Has This Been Tested?

Test Configuration:

• Operating system: Win11
• Graphics Card: irrelevant

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 (header file)
• I have updated the respective chapter in the Stellarium User Guide
• 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 src/**/*.cpp:

• Are possibly unused includes removed?

Files matching guide/**:

• Did you remember to update screenshots to match new updates?
• Did you remember to grammar check in changed part of documentation?

Files matching skycultures/**:

• Did you remember to update skycultures/CMakeLists.txt file respectively to changes in sky cultures?
• Did you remember to define classification parameter in sky cultures (see index.json file)?
• Did you remember to define license parameter in sky cultures (see description.md file)?
• Did you remember to define region parameter in sky culture (see index.json file)?

This is an automatically generated QA checklist based on modified files.

[github-actions]

Hello @gzotti!

Thank you for proposing of the feature.

[alex-w]

Good idea, but I don't like using identical code in 2 places without re-use (computation the elongation along ecliptic) - IMHO this code should be moved in separate method and use in getInfoStringEloPhase() and getCultureLabels() methods.

The second problem - what will see observer on the Moon or on the Mars?

[gzotti]

+1 on code reuse. (There are many other places to do that...)
Name will be limited to Earth use (as are all human cultures)
What about the key words? In the json, "elongation":"western"|"eastern" reads familiar. Or "visible":"morning"|"evening"? Or even "special", to match the internal name?

[alex-w]

"visible":"morning"|"evening" is best IMHO

[alex-w]

Thanks! It’s OK for me, but please check list of names for inner planets in SC

[gzotti]

I am just about to change/add a few entries, but some are incomplete/inconsistent.

[gzotti]

And grmbl, Notepad++ fails to delete parts of Arab (RTL) strings properly.

[sushoff]

I know, you merged it already, I like the new feature

Question:

• does this name only appear to Venus?
• elongation also may apply to Mercury but indeed Jupiter is sometimes mistaken as "evening star" ... did you have this in mind, too?

I'm just asking - either way, it should be mentioned/ explained in the SUG (to be reworked later as you state above).

[gzotti]

The actual names are written in index.json. Venus is clear. For Mercury, I am not aware about a dedicated name currently usable for the modern SC, but I can imagine other SCs could have it, so the technology is here. Elongation-dependent (actually, only separating east/west) names can actually be added to any planet, but won't make much sense. Not sure about other criteria, e.g. is a bright Mars in opposition, rivaling Jupiter, named different from a dimmer Mars anywhere? Such things could still be added later.

People pointing at Jupiter and naming it Evening Star should be instructed to not doing so. "The Evening Star" is Venus, and nothing else. A balloon is no airplane either, despite being "up there".

The SUG instructs SC authors what to specify in the index.json. Maybe, in total, some more words can be provided about SC2.0 in the "Astronomical Concepts" chapter. But as you frequently say, who reads the dedicated Guide?

[github-actions]

Hello @gzotti!

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

[sushoff]

The actual names are written in index.json. Venus is clear. For Mercury, I am not aware about a dedicated name currently usable for the modern SC, but I can imagine other SCs could have it, so the technology is here. Elongation-dependent (actually, only separating east/west) names can actually be added to any planet, but won't make much sense. Not sure about other criteria, e.g. is a bright Mars in opposition, rivaling Jupiter, named different from a dimmer Mars anywhere? Such things could still be added later.

People pointing at Jupiter and naming it Evening Star should be instructed to not doing so. "The Evening Star" is Venus, and nothing else. A balloon is no airplane either, despite being "up there".

LOL aaha, good to know ... of course, I did that several times in astronomy lectures.

Here, I referred to historical observations. If an ancient Babylonian wrote sth like this on a clay tablet, modern Assyriologists would think "ah, the term xxx can refer to both Venus and/or Jupiter".

The SUG instructs SC authors what to specify in the index.json. Maybe, in total, some more words can be provided about SC2.0 in the "Astronomical Concepts" chapter. But as you frequently say, who reads the dedicated Guide?

[gzotti]

Here, I referred to historical observations. If an ancient Babylonian wrote sth like this on a clay tablet, modern Assyriologists would think "ah, the term xxx can refer to both Venus and/or Jupiter".

You could just add some byname for "Jupiter in the Evening Sky" with "visible": "evening" to the "NAME Jupiter" entry in your Babylonian SCs. It will be displayed when eastern elongation is less than 180°. If we need other limits, these must be defined and implemented.

[github-actions]

Hello @gzotti!

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