Great Red Spot position is incorrect ... is there a way to adjust?

Do you have the "Simulate light speed" option on? It's in the "Sky" tab of the "Sky and viewing options" window (F4),

Hi,
This is currently not simulated, it's quite complex because the rotation of jupiter atmosphere is differential.. Light speed simulation is not going to improve that..
Fabien

GRS longitude is reported e.g. in astronomical magazines, maybe there is also an online source. Jupiter's rotation would have to be simulated with a special function the interpolates an additional rotation in a table. Of course, only data for <150 years (?) are available, and future is unpredictable. The table should be a text file (JD vs. longitude) to extend for users. It may not be too difficult, once the data is located... Maybe http://jupos.privat.t-online.de/ is a source, at least for recent years.
G.

I think we need use formula for drift of GRS. This method not very accurate but better current method.

Added semi-experimental coefficient for GRS drift: http://bazaar.launchpad.net/~stellarium/stellarium/trunk/revision/5644

Why is it still unassigned?

The GRS is an atmospheric disturbance, not a topographical feature and as such it is not truly predictable. Its position has been tracked for many years and does not have a predictable position. To get around this the position can be manually changed in the Stellarium system.ini file
 rot_rotation_offset = 250 #just some value good for GRS #old:151
It is therefore not practical to attempt to code this into Stellarium.

Barry

It could be done for past dates, but I don't know where to find a list of GRS longitudes that goes back to before 2010. If such a list was available, say at least one entry per year starting in 1900 or earlier, it may be worth the additional effort beyond Alexander's fix.
This should compute the rot_rotation_offset directly, so that any manual entry in ssystem.ini is overridden. (Wishlist, blueprint?)
G.

We can get a "list" of GRS longitudes since 1830 year on JUPOS website (http://jupos.privat.t-online.de/rChartsOld.htm + http://jupos.privat.t-online.de/rGrs.htm) and for this period just use this data for put GRS in Jupiter's surface. This is not very accurate but better than current implementation (IMHO).

I find a quite good calculation (http://www.projectpluto.com/grs_form.htm) for the GRS and made a patch (see also comments in patch).
The patch is ONLY USED when ssystem.ini:
[jupiter]
rot_rotation_offset=0 # use JupiterGRS patch
rot_rotation_offset=80 # OK on 3/2015 but not constant over time and versions

After the patch you can verify the GRS at
2015-02-26 23:07 UT on picture at https://maximusphotography.files.wordpress.com/2015/03/jupiter-febr-26-2015.jpg
2014-02-25 19:03 UT http://www.damianpeach.com/jup1314/2014_02_25rgb0305.jpg
2013-05-01 10:29 UT http://astro.christone.net/jupiter/jupiter2012/jupiter20130501.jpg
2012-10-26 00:12 UT at http://www.lunar-captures.com//jupiter2012_files/121026_JupiterGRS_Tar.jpg
2011-08-28 02:29 UT at http://www.damianpeach.com/jup1112/2011_08_28rgb.jpg

Stellarium was 2h too early at
2010-09-21 23:37 UT http://www.digitalsky.org.uk/Jupiter/2010-09-21_23-37-30_R-G-B_800.jpg

It is correct since 4 years!!! And hopefully some yeas in the future too. ;-)

For me it is important to have a GRS at the current time, historic would be nice too, but not important.

A fix has been committed as revision 7453 of the trunk branch of Stellarium's Bazaar repository at Launchpad: http://bazaar.launchpad.net/~stellarium/stellarium/trunk/revision/7453

Thank you for the patch!

Sorry. I find one error (patch to the current trunc fixes the longitude of the GRS, I used wrong JD-Date, 2013 instead of 2014).

I also find out, that the used calculation (http://www.projectpluto.com/grs_form.htm) is for viewing from earth (of course).
So you have to turn off 'Simulate light speed'. Then it is correct to the view from earth. I don't know how to fix it for using with 'Simulate light speed' on.

REMEMBER to change also ssystem.ini for this patch:
[jupiter]
rot_rotation_offset=0 # use JupiterGRS patch

Seems method from http://www.projectpluto.com/grs_form.htm has correction for light speed already (this resource is not available in my country).

I played a bit around and found a good solution, where the light speed can be on (as it is default).

The calculation of the System II (cm2) is within 0.5 deg between 2008 and 2015.

The calculation of the GRS is the same, but the rotation is corrected + 25, because the Jupiter Texture is not 0d.

This new patch is againgst the current trunc.

REMEMBER to change also ssystem.ini for use this patch:
[jupiter]
rot_rotation_offset=0 # use JupiterGRS patch

I think current patch is acceptable because he give acceptable data for GRS position in range few years.

Warning! I'm changed the flag for enable JupiterGRS patch (it more predicable now)!

[jupiter]
rot_rotation_offset=-1 # use JupiterGRS patch

Diff: http://bazaar.launchpad.net/~stellarium/stellarium/trunk/revision/7491