Indicate max exposure time for moving objects

[alex-w]

Description

This pull request contain the implementation (optional feature) of indicate the max exposure time for the moving objects within Oculars plugin

Fixes #2752

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 (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?

This is an automatically generated QA checklist based on modified files

[github-actions]

Hello @alex-w!

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

[github-actions]

Hello @alex-w!

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

[10110111]

Does this feature assume that the telescope is installed on a tracking equatorial mount? This should be mentioned somewhere in the docs. Also, if this assumption is true, then the text should only appear for equatorial mount when the selected object is being tracked, or the computation of max exposure time should include the diurnal motion.

[gzotti]

Yes, tracked mount that has been well aligned against axes, is well guided, and is in an altitude range to not suffer from differential refraction, sure. It estimates duration of motion on the sphere against the stars to not exceed 1 pixel (IIRC). 15 years ago nobody would have assumed otherwise. But you can also have motorized tracking on an alt-az mount when you also counterrotate the frame, so "equatorial" is not the criterium.
Max. exposure for the sky just depends on focal length and declination. Not sure if we really must work out how long user can expose a static camera with 10mm lens when aimed at δ=60°.

[10110111]

But you can also have motorized tracking on an alt-az mount when you also counterrotate the frame, so "equatorial" is not the criterium.

Our "Equatorial mount" checkbox controls whether the frame rotates automatically around its optical axis. Regardless of the mount axes, if the frame remains upright, as is currently rendered in stellarium with "Equatorial mount" unchecked, it can't have the same max exposure time as with equatorial mount, even when tracking an object.

But still, the whole this feature is absolutely undocumented AFAICT, so I couldn't even learn about any assumptions that this rather ambiguous label implies.

[gzotti]

It appears that all frame labels are not documented. My hope with in-master guide sources was that features are documented by the respective developers as they are added. :-/

[gzotti]

Mentioned in 666f775