(pen)umbra issues [sat plugin]

[axd1967]

Expected Behaviour

Actual Behaviour

Describe or maybe attach a screenshot?

Steps to reproduce

1. set location as specified below
2. advance time to 2024-05-13 011257UTC+2
3. enable (penumbra) display
4. clear "show (pen)umbra at 419km"
5. select ISS; observe ISS altitude is reported 419km
6. observe plot
   
7. enable penumbra at 419km
   

BUG

1. (penu)umbra is different although selected altitude is the same
2. the point where the ISS becomes invisible is relatively far from penumbra. in fact, the segment where the ISS enters penumbra could be colored differently (suggestion: adopt penumbra color setting?). (Additionally, the button does nothing when a satellite is selected, another indication that something is wrong in the UI approach.)

ISS TLE data at time of bug report: (epoch 2024-05-11 1153 UTC)
1 25544U 98067A 24132.49518146 -.00008485 00000+0 -13500-3 0 9998
2 25544 51.6377 137.3000 0003376 160.7195 340.3320 15.51165706452859

location: N 51° 1' 39.78" E 3° 42' 17.66" 10m

• This is related to sat plugin: umbra at "distance" (should be "altitude") does not correspond to selected sat's umbra #3100
• Please see also sat plugin: umbra at "distance" (should be "altitude") does not correspond to selected sat's umbra #3100 (comment)
• the "show umbra/penumbra" should operate independently of whether a satellite was selected or not. (Agreed, this demands for different colors...). There is a UI issue in the choice of three checkboxes.

System

• Stellarium 24.1+
  Version 24.1.132-a69fbf7 [master]
  Based on Qt 5.12.8

Same issue in latest:
Stellarium 24.4+
Version 24.4.8-0de39da [master]

Operating System: Kubuntu 20.04
KDE Plasma Version: 5.18.8
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel Version: 5.4.0-181-generic
OS Type: 64-bit
Processors: 8 × Intel® Core™ i7-10510U CPU @ 1.80GHz
Memory: 15.3 GiB of RAM

Logfile

If possible, attach the logfile log.txt from your user data directory. Look into the Guide for its location.

[gzotti]

The satellite vanishes between penumbra and umbra borders. These are results from the used satellite library code that classifies into "visible"/"hidden" and not much more. We are talking about a few seconds.
The "shadow in ...km altitude" code necessarily leaves out ellipsoidal effects, while the altitude of the satellite is above the WGS84 ellipsoid. It should still provide a rough idea.
It's good enough for me to not throw away the function. But it will never be good enough for some other users.
At this point you are again cordially invited to get involved, reverse engineer the code, fix what you find broken, and propose your solution.

[github-actions]

Hello @axd1967!

Thank you for this suggestion.