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Best GRS Transit Reference?

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#1 GoFish

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Posted 22 June 2019 - 06:01 PM

Trying to plan some outreach events where guests can observe the red spot on Jupiter.  I am having a heckuva time getting consistent results for the GRS transit timing from among several resources.

 

I am in MDT zone, offset -6 from UTC.

 

An example of the discrepancies for the evening of June 24, 2019, for example:

 

8:48 PM - Sky Safari Pro 6 (minor body orbit data updated today)

9:19 PM - Sky and Telescope calculator https://www.skyandte...great-red-spot/

8:47 PM - Project Pluto https://www.projectp...om/jeve_grs.htm (UTC 14:47 on June 25)

9:02 PM - http://www.acquerra....re/jupiter.html

 

Is there an accepted "gold standard" for these timings?

 

 

 


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#2 DLuders

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Posted 22 June 2019 - 06:15 PM

ShallowSky has a good interactive calculator for the Great Red Spot; if you advance today's time a few hours you can see when the GRS is visible --  http://www.shallowsk...y.com/jupiter/ 


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#3 GoFish

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Posted 22 June 2019 - 06:17 PM

Thanks, DLuders. I had tried to use that site before I posted, but couldn’t (still can’t) reach it?

 

If you can get to it, ask it about June 24 wink.gif



#4 RaulTheRat

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Posted 22 June 2019 - 06:19 PM

The Android app Jovemoons works well for me.
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#5 goodricke1

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Posted 22 June 2019 - 06:22 PM

The discrepancies can arise from the light travel time between Jupiter and Earth - some 35 minutes at present. Stellarium has the real-time value, once the appropriate check box has been marked.



#6 marsbase

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Posted 22 June 2019 - 06:33 PM

I think you will like this one.

Shows the red spot, moons and eclipses. You can move the time ahead to see what will be up.

 

http://shallowsky.com/jupiter/



#7 GoFish

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Posted 22 June 2019 - 06:34 PM

The discrepancies can arise from the light travel time between Jupiter and Earth - some 35 minutes at present. Stellarium has the real-time value, once the appropriate check box has been marked.

Who would care to know the “as-viewed-from-Jupiter” time when transit occurs?  “As-viewed-from-Earth” time is a lot more useful. undecided.gif

 

What time does Stellarium give for the June 24/25 transit?  I don’t have it installed on my tablet. 



#8 GoFish

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Posted 22 June 2019 - 06:38 PM

I think you will like this one.

Shows the red spot, moons and eclipses. You can move the time ahead to see what will be up.

 

http://shallowsky.com/jupiter/

Nice. It seems to agree with the Sky and Telescope timing of 9:19 pm MDT on June 24. 



#9 REC

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Posted 23 June 2019 - 10:50 AM

S&T sells a great Jupiter App for $2.99. It shows and tells you what is happening every day on the planet.



#10 REC

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Posted 23 June 2019 - 10:53 AM

Trying to plan some outreach events where guests can observe the red spot on Jupiter.  I am having a heckuva time getting consistent results for the GRS transit timing from among several resources.

 

I am in MDT zone, offset -6 from UTC.

 

An example of the discrepancies for the evening of June 24, 2019, for example:

 

8:48 PM - Sky Safari Pro 6 (minor body orbit data updated today)

9:19 PM - Sky and Telescope calculator https://www.skyandte...great-red-spot/

8:47 PM - Project Pluto https://www.projectp...om/jeve_grs.htm (UTC 14:47 on June 25)

9:02 PM - http://www.acquerra....re/jupiter.html

 

Is there an accepted "gold standard" for these timings?

I would say that the S&T App would be the gold standard for Jupiter. You can even get a visual of the moons going back and forward on the chart.



#11 SabiaJD

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Posted 23 June 2019 - 02:04 PM

S&T App is good app, but GRS Transit could be off by 40 minutes. So start observing earlier that the time generated.

 

Project Pluto may be closer to the time of transit.

 

Have yet to be able to see a transit of GRS on Jupiter to determine the GRS CM .

 

 

Longitude drift chart of GRS from WinJup   (close to 312 degrees CM2)       http://jupos.privat....ne.de/index.htm

 

I would use the 312 CM in the software Jupiter 2. http://www.astrosurf...piter/index.htm



#12 Dave Mitsky

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Posted 23 June 2019 - 05:16 PM

Project Pluto may be closer to the time of transit.

I believe that's correct.



#13 GoFish

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Posted 23 June 2019 - 05:32 PM

If ProjectPluto is taken as the most correct, then SS6 is the closest estimate from among the resources I consulted. The S&T website differs (lags) by around a half hour. 

 

Very unsatisfying!  mad.gif



#14 ascii

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Posted 23 June 2019 - 06:13 PM

If SKySafari 6 is good, the iOS "Jupiter Moons" app from S&T should be good too.  They pretty much match, which is unsurprising.  The S&T apps are written by the folks at Simulation Curriculum, the makers of SkySafari.


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#15 SabiaJD

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Posted 23 June 2019 - 06:40 PM

If SKySafari 6 is good, the iOS "Jupiter Moons" app from S&T should be good too.  They pretty much match, which is unsurprising.  The S&T apps are written by the folks at Simulation Curriculum, the makers of SkySafari.

But the S&T online GRS calculator times of  "GRS"  off.  The time of GRS transit published in thier monthly magazine is correct!  Guess they don't use their own online calculator.


Edited by SabiaJD, 23 June 2019 - 06:41 PM.

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#16 Special Ed

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Posted 23 June 2019 - 08:40 PM

Since the GRS drifts, it all depends on how often the various calculators are updated.  The GRS can be most easily observed for an hour on either side of the scheduled transit so there is a two hour window.  The thing to hope for is if this window coincides with Jupiter near culmination.



#17 ascii

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Posted 25 June 2019 - 06:32 PM

I observed the transit of the GRS last night.  Just eyeballing it in my scope, I'd say SkySafari 6 and the S&T JupiterMoons app showed a time that was about 15 minutes prior to the actual event.



#18 GoFish

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Posted 25 June 2019 - 08:35 PM

I observed the transit of the GRS last night.  Just eyeballing it in my scope, I'd say SkySafari 6 and the S&T JupiterMoons app showed a time that was about 15 minutes prior to the actual event.

This is consistent with a report in a different thread that suggests the S&T website calculator prediction was closer than the others. 



#19 Dave Mitsky

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Posted 25 June 2019 - 10:25 PM

June 26 06/26/2019 @ 09:06 UT S & T online calculator

 

June 26 8:37 UT S & T Magazine

 

26 Jun 2019 8:34 UT Project Pluto
 

It seems that the magazine and Project Pluto predicted GRS transit times are more congruent.

 

Dave

 


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#20 Special Ed

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Posted 26 June 2019 - 06:31 AM

June 26 06/26/2019 @ 09:06 UT S & T online calculator

 

June 26 8:37 UT S & T Magazine

 

26 Jun 2019 8:34 UT Project Pluto
 

It seems that the magazine and Project Pluto predicted GRS transit times are more congruent.

 

Dave

 

If you split the difference you'll get the most accurate result--but they're all pretty close.  The center of the GRS is at 311 degrees (System II).

 

At 0834 UT, System II was 300 degrees.  At 0906 UT, System II was 319 degrees.  At 0853 UT, System II was 311 degrees.



#21 GoFish

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Posted 26 June 2019 - 02:12 PM

When you put it that way, it seems like an insignificant discrepancy, +8 or -11 degrees. 

 

But in the context of the GRS being well placed for observation for only around 50 minutes either side of transit, then 13-minute and 21-minute discrepancies for the transit time seems excessive for a calculation that is well understood?



#22 Special Ed

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Posted 26 June 2019 - 05:28 PM

It's well understood but the GRS drifts so accuracy is dependent on timely updates.


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#23 SabiaJD

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Posted 27 June 2019 - 09:00 AM

 There is a software that allows the user to input  the current observed Longitude. From observation from the WinJupOS website, or manually by the user.

 

Of course you would have to time the Central Meridian the passage of the GRS yourself for a more accurate  future transits.

 

Jupiter 2, written for a few languages.  http://www.astrosurf...exprincipal.htm

.

 

This is the only one I found so far.


Edited by SabiaJD, 27 June 2019 - 10:47 AM.


#24 GoFish

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Posted 27 June 2019 - 10:30 AM

 There is a software that allows the user to input  the current observed Longitude. From observation from the WinJupOS website, or manually by the user.

 

Of course you would have to time the Central Meridian the passage of the GRS yourself for a more accurate  future transits.

 

Jupiter 2, written for a few languages.  http://www.acquerra....re/jupiter.html.

 

This is the only one I found so far.

Thanks, John. 

 

The link in your post shows up in my browser as a simple transit calculator (9:02 pm MDT for my hypothetical test on June 24 — see OP). I did not see a way to adjust the results to reflect updates to the GRS longitude?


Edited by GoFish, 27 June 2019 - 10:31 AM.


#25 SabiaJD

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Posted 27 June 2019 - 10:46 AM

Wow, I got it wrong twice!  Thanks for point this out. This is the correct page, select English and scroll to the bottom of the page.

 

http://www.astrosurf...exprincipal.htm


Edited by SabiaJD, 27 June 2019 - 10:46 AM.



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