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when to see Jupiter's Great Red Spot

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#1 FlorinAndrei

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Posted 24 November 2012 - 05:02 PM

The GRS rotates with the planet, so it's not always visible. Here's one way to calculate when it should be visible:

http://www.wolframal...=great red spot

More examples related to astronomy:

http://www.wolframal.../Astronomy.html

They also have an app for the iPhone, Android and all the tablets, which works just like the website.

#2 frito

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Posted 24 November 2012 - 05:08 PM

if you have Skysafari plus or better for android or iOS i have confirmed on multiple observing sessions that it accurately depicts both the location of the GRS as well as the 4 Galilean moons and shadow positions when they pass in front of the planet. if you move forward in time within the program it will accurately show you where they will be later on that day etc.

#3 jfaust75

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Posted 24 November 2012 - 06:36 PM

It should be visible tonight around midnight here. Hoping to see it

#4 frito

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Posted 24 November 2012 - 06:43 PM

it should be easily visible from 8 pm PST till past 11 pm so i would start looking for it around 11 pm eastern time for you. i regulary see it with good or better seeing in my XT8 with 6.3, 7.5 and sometimes my 10mm Plossl so you should not have problems seeing it if conditions are right in your area tonight

#5 Seldom

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Posted 24 November 2012 - 08:24 PM

Interesting, Sky & Telescope puts the transit at 4:53 UT 11/25, and that works out to 9:53 MST 11/24, and S&T says the GRS (Great Latte Spot) should be visible for 50 minutes from transit to rise or set. Wolfram Alpha puts transit an hour earlier and says it should be visible for more than two hours either side of transit.

Who do you trust? (10:00 PM MST, and S&T was right on time.)

And kudos to Starbucks for managing a spill that would drown the earth.

#6 frito

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Posted 24 November 2012 - 08:29 PM

skysafari hasn't been wrong yet for me so ill trust it :)

#7 wky46

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Posted 24 November 2012 - 09:14 PM

Thanks for the links Florin :)

#8 Tony Flanders

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Posted 25 November 2012 - 06:40 AM

Interesting, Sky & Telescope puts the transit at 4:53 UT 11/25, and that works out to 9:53 MST 11/24, and S&T says the GRS (Great Latte Spot) should be visible for 50 minutes from transit to rise or set. Wolfram Alpha puts transit an hour earlier and says it should be visible for more than two hours either side of transit.

Who do you trust?


Wolfram Alpha is using very old data for the GRS position. They state it's at longitude 138, whereas we're currently using 184. As you can see from the JUPOS website, even we are a bit low -- I should update it to 190 or thereabouts.

Tony Flanders
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#9 Skooter

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Posted 25 November 2012 - 07:49 AM

S&T has been precise to the millisecond, as far as I can tell from 600 million miles away. :grin:

#10 Eric63

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Posted 25 November 2012 - 09:20 AM

I have the Jupiter Atlas app for Ipod but does not properly compute the transit time when a time zone lag is computed based on your location. After you enter your location in the app, you need to set the time lag to 0 hours each time you start the app. With that done, it then matches sky safari and S&T.

#11 BoriSpider

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Posted 25 November 2012 - 11:44 AM

I use the computer program Jupiter2 . It's free
and works well.

#12 frito

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Posted 25 November 2012 - 12:44 PM

I use the computer program Jupiter2 . It's free
and works well.


i have it and use it to monitor the position sometimes but you must correct the location of the GRS it defaults to 129 degrees and thats wrong. fortunately it has a link to a website with the correct and current location. oh it will also show it when its at the very sides as if you might be able to see it when really you cannot yet. otherwise it is a great program.

#13 Seldom

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Posted 25 November 2012 - 02:52 PM

you must correct the location of the GRS it defaults to 129 degrees and thats wrong. fortunately it has a link to a website with the correct and current location.


Just guessing, but from the screenshots on the Jupiter2 webpage it looks like the default value for the GRS longitude may have been right for the time the program was compiled, and the data on the link to the correct transit time is a raster graphic that would be hard to extract the correct transit time from. Not really a problem because you can save the correct longitude if you "quit saving parameters".

#14 Tony Flanders

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Posted 25 November 2012 - 04:37 PM

But from the screenshots on the Jupiter2 webpage it looks like the default value for the GRS longitude may have been right for the time the program was compiled.


No doubt. The GRS has really been zipping along in recent years, often gaining more than one degree per month.

The data on the link to the correct transit time is a raster graphic that would be hard to extract the correct transit time from.


Don't fret about it! The GRS is enormous, covering a good 20 degrees of longitude. You would need extraordinarily careful observation to tell a difference of plus or minus 5 degrees.

#15 Dennis_S253

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Posted 25 November 2012 - 06:29 PM

Just to be sure what your all saying. In the Jupiter 2 program. One has to change the "absolute position of Jupiter box" from 129 to 188?

#16 Seldom

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Posted 25 November 2012 - 07:30 PM

Just to be sure what your all saying. In the Jupiter 2 program. One has to change the "absolute position of Jupiter box" from 129 to 188?

If you click the "absolute position ON Jupiter" link you will see a plot of current GRS positions. That plot will show you that 188 is a pretty good longitude for now, but it keeps changing, so check every 3 to 6 months.

#17 Dennis_S253

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Posted 25 November 2012 - 08:29 PM

Ok thanks, Stellarium is really close tonight also. I use to think Stellarium was way off but I was using the 129 # in Jupiter 2. I'll have to try it a few more nights.

#18 FlorinAndrei

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Posted 25 November 2012 - 11:55 PM

Wolfram Alpha is using very old data for the GRS position. They state it's at longitude 138, whereas we're currently using 184.


It is off, indeed, I could plainly see it in the eyepiece.

Well, I sent them feedback on that query, they usually fix their bugs.

#19 Tony Flanders

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Posted 26 November 2012 - 08:29 AM

Well, I sent them feedback on that query, they usually fix their bugs.


Unfortunately, this isn't a matter of fixing a bug as computer programmers usually view it. This requires ongoing maintenance, since the GRS is constantly drifting in unpredictable ways.

Nobody wants to devote a person to doing periodic maintenance on a computer program; it's a logistical nightmare. It's different for us at S&T. Astronomy is our bread and butter, and we have to publish GRS tables in the magazine anyway. So we need to stay on top of the GRS longitude whether we like it or not.

Tony Flanders
Associate Editor, Sky & Telescope

#20 Seldom

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Posted 26 November 2012 - 11:15 AM

Too bad that http://jupos.privat....ine.de/rGrs.htm doesn't publish the data in text/numeric form as well as raster graphic. Then maybe programmers could update the longitude for their applications automatically via the web.

#21 FlorinAndrei

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Posted 27 November 2012 - 03:03 AM

Tony, they could pull that data out of a reliable feed periodically, if there is such a thing somewhere. This is not 1980 anymore, not all data is maintained by hand these days; you let the systems do it. I make a living as an IT guy in the Silicon Valley, I'd say for a site like Wolfram Alpha these days pulling live info out of external sources all the time and blending it with your own stuff is something you take for granted. WA do it all the time for many other things, e.g. weather conditions and forecast. So some infrastructure must be in place. We do stuff like that too, and we're smaller than WA (and in a different sector).

But it does require a stable and trusted source of data for the GRS position that is willing to allow them to use their numbers - and whether such a thing exists or not, I have no idea.

They may also not care about it, since the audience for astronomy info is pretty small. I don't know, I'm not privy to their operations and policies. But they do seem to be obsessive perfectionists, so hopefully they'll do at least a one-off fix, if a steady stream of updates is not feasible. That would be good for a year or so.

We'll see.

#22 FlorinAndrei

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Posted 18 December 2012 - 02:10 AM

I just got an email from WA saying:

We have received your feedback regarding Wolfram|Alpha.

The issue you reported has been fixed on the site. See http://www.wolframal...=great red spot

Thank you for helping us improve Wolfram|Alpha.

Best wishes,


I like these guys.

#23 mtymak

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Posted 19 December 2012 - 02:54 AM

A beautiful clear night here, at about 23:30pm i point my 130mm Newt with a 6mm EP to Jupiter and i believe i saw the GRS.

I'm located at 25°N 99°W and i have the Jupiter2 program, i
set the absolute position to 188 and according to the program.... yes the GRS was visible

Do you think i made it?? or could be my imagination?.. :scratchhead:

Best regards
Mauricio

#24 Tony Flanders

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Posted 19 December 2012 - 06:25 AM

A beautiful clear night here, at about 23:30pm i point my 130mm Newt with a 6mm EP to Jupiter and i believe i saw the GRS.


Almost certainly yes. It's really not all that hard to see once you recognize what it looks like. Always pretty subtle, though -- at least in its current pale-pink incarnation.

#25 REC

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Posted 19 December 2012 - 10:20 AM

It will be visible tonight from 8-11 pm EST. Check out S&T for times each day.

BTW...I was looking at Jupiter last night and it was great, high in the sky at 10pm. I had a light blue filter (80A)at 100x and the belts were great! Supposed to be better seeing here tonight, so will have another look for the red spot.

Bob






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