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Stellarium / stellarium

Stellarium is a free GPL software which renders realistic skies in real time with OpenGL. It is available for Linux/Unix, Windows and macOS. With Stellarium, you really see what you can see with your eyes, binoculars or a small telescope.
https://stellarium.org
GNU General Public License v2.0
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Titan Eclipse events not accurate? #3727

Open JanHatt opened 6 months ago

JanHatt commented 6 months ago

Hi, have I found a bug?

Expected Behaviour

Start and end of Titan phenomena should be in line with prediction e.g. by the IMCCE https://ssp.imcce.fr/forms/satellites-events

Actual Behaviour

Shadow events are indeed accurate when compared to IMCCE prdictions, eclipses are not. E.g., for the Titan eclipse of 27.10.2024, IMCCE (with JPL ephemeris) predicts 20:51 UT Eclipse disappear (start) and 21:44 UT Eclipse reappear (start). Stellarium's simulation is way off.

However, IMCCE predicts a shadow transit of Titan on Saturn for the 20.11.2024 between 19:38 and 22:11 UT, which fits perfectly to Stellarium.

Same with all other eclipses/shadow transits by Titan in 2024/25. Did not check other moons.

Steps to reproduce

System

regards, Jan

gzotti commented 6 months ago

Uh! Switching off light time correction reproduces the shadow ingress.

IIRC, we don't specifically tweak anything for shadows, they should just happen when the positional computation is correct. Now, we need positional comparison options.

github-actions[bot] commented 6 months ago

Hello @JanHatt!

OK, developers can reproduce the issue. Thanks for the report!

worachate001 commented 6 months ago

The planet's oblateness must be taken into account. The current simulated shadow looks circular from my experiments.