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Setting the correct Jupiter Red Spot position in Stellarium


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Further to my post <here> and a bit of hacking around on my laptop's Program Files directory, I've managed to fix the Red Spot position for Jupiter in Stellarium by setting:

rot_rotation_offset = 127

In the [jupiter] section of the text file:

C:\Program Files\Stellarium\data\ssystem.ini

Hope that's useful to you Stellarium users.

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Cheers for the tip, that had been bugging me! However, I found it matched the predictions for GRS transits on skyandtelescope.com when the offset was set to 177, this depends on the predictions on skyandtelescope being accurate...

Edited by toml42
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That's with option "Simulate Light Speed" OFF by the way.

- a different value would be required if you have this option on.

I found it matched the predictions for GRS transits on skyandtelescope.com when the offset was set to 177

I just based my value on a meridian crossing of 0:46 this morning, as reported by Dave - which ties in with my own experience last night. Maybe check the light speed setting as above.

Edited by great_bear
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On the Sky and Telescope website it states the following:

'The predictions assume the Red Spot is at Jovian System II longitude 157°, based on historical trends noted by JUPOS. If the GRS moves elsewhere, it will transit 1 2/3 minutes late for every 1° of longitude greater than 150° or 1 2/3 minutes early for every 1° less than 150°.

Features on Jupiter appear closer to the central meridian than to the limb — and thus are well placed for viewing — for 50 minutes before and after their transit times.'

This is, correctly, showing that the GRS actually drifts in Latitude and longitude and this 'magic' figure (currently 157 degs in system II) is the one that you will need to update occasionally in the appropriate box or data file. Failure to do this will result in the predicted times of your own software being 'out'. Do not forget that the S&T website give the predictions in U.T (G.M.T) and you would need to add 1 hour for BST (Daylight Saving Time).

Before I go into information overload I will finish with the GRS predictions for September, with thanks to Sky and Telescope, so that you can check out your software times.

Red Spot Transits in 2010

September 1: 8:15, 18:10; 2: 4:06, 14:02, 23:57; 3: 9:53, 19:48; 4: 5:44, 15:39; 5: 1:35, 11:31, 21:26; 6: 7:22, 17:17; 7: 3:13, 13:09, 23:04; 8: 9:00, 18:55; 9: 4:51, 14:46; 10: 0:42, 10:38, 20:33; 11: 6:29, 16:24; 12: 2:20, 12:15, 22:11; 13: 8:07, 18:02; 14: 3:58, 13:53, 23:49; 15: 9:45, 19:40; 16: 5:36, 15:31; 17: 1:27, 11:22, 21:18; 18: 7:14, 17:09; 19: 3:05, 13:00, 22:56; 20: 8:52, 18:47; 21: 4:43, 14:38; 22: 0:34, 10:29, 20:25; 23: 6:21, 16:16; 24: 2:12, 12:07, 22:03; 25: 7:59, 17:54; 26: 3:50, 13:45, 23:41; 27: 9:37, 19:32; 28: 5:28, 15:23; 29: 1:19, 11:15, 21:10; 30: 7:06, 17:01

Good hunting.

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  • 3 weeks later...

hi members,can u help me with this changing stellarium ot_rotation_offset = 127 have located the file in systems after i change it from 250 to 127 it asks me to save this setting,,,yes,then to name it,, ok call it systems,,it says file all ready exsits do you want to replace it ,,yes,,access denied,what am i doing wrong.??

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Thanks for that - I was having the same difficulty saving the change. Should the 'offset' be 127 or 177. Both are mentioned in this thread.

I'd also be interested to know. I have light-speed simulation on, so would it be 127?

Also, out of curiosity, why would one have light-speed off? I thought that option meant that what you saw on Stellarium matched what you saw in your eyepiece, so surely one would always want it on for observing?

Edited by Breakintheclouds
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Just changed mine with 177 and light speed simulation on !

tried 127 1st, but was still out, but 177 seems accurate enough,

also added 4 fainter Jupiter Moons that Rikalium posted

thanks Rik

anyone know if u can add ISS and Current Comets ?

many thanks James

heres Rik's Moon info that can be copied and pasted in after other Jup Moons


Edited by AztecastroMcJ
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Just gave this a try. Skyandtelescope.com says there's a transit of the GRS at 0450 tomorrow morning local time. I found a value of 140 best reproduced this in Stellarium, with simulate light speed on.

Oh, and in case anybody is using Linux, the relevant file can be found \t /usr/share/stellarium/data/ssystem.ini

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  • 2 weeks later...

the only way I could save the change was to 'right click' the ssystem.ini file, go to 'Properties' and then 'Security' and change the privileges so that I was allowed to edit. Saved ok then.

I had the same problem saving the file after editing. I found this thread is very useful thank you GB.

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  • 4 years later...

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