Predicting Jupiter's GRS

[mike.brightmore]

The best chance of seeing the Red Spot is round about the time it crosses the planets central meridian. As we are coming up to the best views of Jupiter we will have for several years I want to be sure that I have an accurate programme to predict meridian transits of the GRS and transits of Jupiter's moons. Following advice on SGL I have changed the rot_rotation_offset value in Stellarium's ssystem file to 127 and that has improved Stellarium's predictions considerably but it is still about 30 minutes out.

The most accurate software I have found (also previously recommended on SGL) is a beautiful little programme from the Castle Point Astronomy Club (CPAC) called 'The Planets (version 2.02)' downloaded from www.cpac.org.uk

I have also just downloaded the 'Great Red Spot Transit Table 2011 - 2012' from the Sky and Telescope web site. The transit times given here are in close agreement with the CPAC programme.

Just watching the Io shadow transit (the black spot of the shadow is crystal clear) and the CPAC programme was spot on for this as well.

So have I got all the bases covered now for the Jupiter season or is there a revised longitude offset value for Stellarium?

[Dave Smith]

As a member of CPAC I have used "The Planets" for a number of years. If you use it for a few years it will be necessary to update the longitude of Jupiter. There is a current value on the Sky & Telescope website. The current value is 173. With the program is a data file "location" which can be opened in Notepad. The very first figure is Jupiter's longitude. If necessary change it and re-save and the GRS predictions will be accurate.

The same program is also useful for predicting the positions of Saturn's Moons.

Dave

[teleskopjo]

Actually the current value of the GRS longitude L2 = 168 degrees.

This is from

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Best regards