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Eastridge

GRS :Who's wrong, Stellarium, skyandtelescope or me ( I can guess!)

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OK, went out Great Red Spot hunting on Jupiter last night.  The skyandtelescope's 2014 list said it would be central 17.55 UT / GMT.

Couldn't get it at all, have 'thought I'd seen it' a number of times prevoiusly but last night was prepared to put the time and patience in to just keep looking until I definitely got it.  I could see what seemed like 'smaller' variations in the bands but nothing like GRS.

I fired up Stellarium and that showed GRS right on the edge of the planet at that time (17.55).  I have checked my basic settings in Stellarium - location settings and date and time settings all correct.   I then went to some other sites thinking maybe skyandtelescope had had a 'typo' but other sites said the same.

I trust both sources so accept I must be doing something wrong, anyone any ideas what it could be?

Anywhere else I could look?  I know the 'Jupiter moons site' which is great for the moons but that isn't detailed enough for the GRS.   

At the same time I have failed miserably to find a way to make Stellarium give zoomed in close up's in 'Inverted' image as my dob will, is there one?  A plug in maybe? I appreciate that for general mapping and finding you want it correct way, but the mental gymnastics in trying to rotate the planet in my mind to match my EP view was too much for me!

Any help appreciated, thanks.

Sharon.

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I cannot help you with beter information or a better site.

I will say however that the GRS is a weather feature and yet appears to be treated as if it is a stable constant satellite.

As we cannot get the weather with great accuracy here in the UK I would have assumed that whatever is used for Jupiter is even more suspect.

I would assume that someone predicted the GRS positions at something like every 6 months or even annually, meaning that in the intervening time the real position can change with respect to the predicted.

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I'm not sure if it will work but I recall it being mentioned that if you go into the Sky & Viewing tab on Stellarium and under the Sky section there should be a box that says 'Simulate light speed' tick that and I think it shows the correct positioning.

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Stellarium needs some of it's startup paramaters "tweaked" to give an accurate GRS position I seem to recall. I use the SKy & Telescope applet and find it very accurate.

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I too have found the Sky & Telescope info for the GRS to be 'spot on'  :smiley: ( groan )

Regards, Ed.

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the sky and telescope site I have found is very accurate. I tend to run the utility rather than look at the list though. no reason and not checked if there's differences.

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I agree with the above. S&T is reliably correct.

Stellarium can be wrong for two reasons, both highlighted by previous posters. The GRS moves with time, so you need to update the start up parameter which sets it's position.

Secondly, I think by default it shows the time the event happens, rather than as we see it in earth. The 'simulate light speed' delays it by the light travel time from Jupiter which puts GRS in the position we see it. It changes relative to Jupiter's distance from us but around 35 to 40 minutes is usual I think. This obviously applies to the Gallilean moons positions as well as GRS.

Stu

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As for making Stellarium give an inverted view, set up the Oculars plugin.

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Thanks everyone,   Good to know it wasn't something I was doing stupid and that it seems I can correct Stellarium.  Will try that and the plug in later.

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I find that the S&T app for smartphones (if you have one) is accurate and graphically clear and simple to use

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I find that the S&T app for smartphones (if you have one) is accurate and graphically clear and simple to use

 more specifically, if you have an Apple product.  Sadly only their (nice) SkyWeek app is currently available for phones running Android.

http://www.skyandtelescope.com/apps

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Thanks for the correction John - I assumed that it was available for Android too. Shame - it's a nice little app that I use all the time

Kerry

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Thanks JB80&BigMac for reminder bout the lightspeed, good point,

but that would also affect the position of the moons as well, they were the same in my two Stellarium versions whereas the rot-param needed different settings to get the spot in the right place.

In fact both versions were unticked on lightspeed ! and I hadnt noticed !! but my excuse is that I'm only on binoculars at the mo and visuals on the moons are not easy!!!

With binoculars the position of the red spot is academic for me anyway, just a software thing for cloudy nights :)

I expect wasisname just adjusted between the compiling times of the two versions, no worries, just  curiosity.

Having now set the lightspeed I was surprised at how small the change was, I probably would not have noticed in binocular even if I had been paying attention !!

So that was interesting, thanks Eastridge for raising it :)

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7:12 PM tonight my first ever pic of the GRS

even managed to get a faint moon in this shot will need to check to see which one 

post-34443-0-61129100-1392940505_thumb.p

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Stellarium will always have it 30 to 50 mins too early unless its adjusted for the light travelling from the planet and this varies depending on where in our two respective orbits we are in relation to each other.

jupiter also roatates really fast , taking less than 10 hours to do a full rotation so the grs goes from one side to the other in less than 5 hours meaning any delay can show the spot to be considerably out of position. In addition to this we must remeber that the panet is a sphere so the grs appears to move slowest when on the edges of the disk than the cente so it will take a while to appear then whip across the middle then take time to disappear..... depending how close it is to the centre will affect how much out of position it appears to be unlesscorrected for light speed.

Cheers

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I have found the best estimator for the Great Red Spot is WINJUPOS (freeware).  As the GRS drifts you can easily add a correction (there is a link within the software) - I update mine two or three times a year.  The generated image of Jupiter within the software is then accurate and you can easily animate a night to see what will be visible.  It is also accurate for the positions of Jupiter's Moons, shadow transits and occultations etc.  As a bonus the software also has similar facilities for the other planets as well.

Another similar piece of software is this one:  http://www.astrosurf.com/rondi/jupiter/index.htm  

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I have loaded the Occular plug in for Stellarium and that does exactly what I'd hoped + the bonus of Telrad circles which will be really helpful.  Adjusted to 'light speed' and hubby (ex software engineer ) went into the .ini file as suggested and reset 'the rot offset' so now all aligns.

So, thanks everyone who made suggestions.  I'll now look at the other sites suggested as they look interesting too.

Thanks again.

Edited by Eastridge

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