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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.
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Phoebe position iincorrect #230

Closed kwbeverage closed 1 year ago

kwbeverage commented 6 years ago

Expected Behaviour

Correct position shown for Phoebe

Actual Behaviour

For a given time Phoebe is shown in an incorrect location. Checked results against ephemerides acquired from the MPC Natural Satellites Ephemeris Service and Saturn Viewer 2.9 website. See screen capture and text file for comparison.

Steps to reproduce

Installed current version (0.18.1) which shows the same position as previous install (0.17.0).

System

Attachments: stellarium-014

phoebe_data.txt

gzotti commented 6 years ago

https://github.com/Stellarium/stellarium/wiki/FAQ#some-moons-are-in-another-position-than-they-should-be

Stellarium is not finished. You are cordially invited to help.

alex-w commented 6 years ago

Phoebe has simple elliptic orbit at the moment and of course this solution is not accurate. We need to implement PH12 (ftp://ftp.imcce.fr/pub/ephem/satel/ph12/README.txt) and HTC 2.0 (ftp://ftp.imcce.fr/pub/ephem/satel/htc20/ReadMe.txt) for Saturnian moons.

piellepi commented 1 year ago

hi! I'm using version 1.1 of stellarium but Phoebe's position is still greatly incorrect. instead in stellarium web the position seems correct and comparable to the one generated by IMCCE software

this is the position in PC version febe pc

this is in the web version febe web

and this is the position from IMCCE febe imcce Phobe here is marked with a cross...

thanks Pierluigi Panunzi

gzotti commented 1 year ago

Yes, and therefore this issue is still open.

worachate001 commented 1 year ago

I'm investigating the cause of error and found that orbital elements of the satellite are wrong for the epoch. I will correct it soon and try to check (and correct them if needed) others before the release of version 23.2.

gzotti commented 1 year ago

@alex-w mentioned PH12, so this (or even better) would be preferred over Kepler elements.

worachate001 commented 1 year ago

I read that PH12 ephemeris is available for only the years 1875-2022. The alternative method that I'm thinking about is using mean orbital elements that include rate of changes (in longitude of ascending node, etc.) , derived from hundred years of elements. But it would be original work.

gzotti commented 1 year ago

OK, yes, PH12 is no solution then. Note that the current way to describe moon orbits is relative to the planet equator, which is not what is usually found in the literature. I don't know the origin of this model. If you make variable orbits like this, you must also change the KeplerOrbit class.

github-actions[bot] commented 1 year ago

Hello @kwbeverage!

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

github-actions[bot] commented 1 year ago

Hello @kwbeverage!

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