Did I see it (jupiter) right?

[starhopper13]

Last night I went stargazing and saw Jupiter in all its glory. Though I have a confusion..

I use Celestron's astromaster 130 eq. First I pointed at Jupiter using my 20mm (correct) eyepiece, then switched to the 10mm (not correct) eyepiece to see it better. The belts were obvious, and the lighter belt seemed to have a dark "spot" near it, on the top left corner of the disk, which I assumed to be the GRS. I looked several times and it seemed to stay so I guess it really was there. 

However, after an hour of trying to point at fainter stars with my RDF, my eyes had become somewhat fatigued. When I tried to look at Jupiter afterwards, the spot seemed to have moved to the upper right. What struck me was, does the spot really move that fast or was it my tired eyes seeing wrong things? 

Edited June 12, 2019 by starhopper13

[Geoff Barnes]

Hi starhopper13, It takes the spot about 4 hours to transit across the face of Jupiter, I think it does a complete orbit in about 9 hours.

It may well have been a shadow transit of one of Jupiter's moons which would cross in an hour or two, especially if it was nearer the top corners when you saw it, the Great Red Spot sits nearer the equator of the planet.

Edited June 11, 2019 by Geoff Barnes

[Stu]

@starhopper13 what time were you observing? I see you are in Bangladesh but we can check to see what it was you are likely to have seen.

[starhopper13]

16 minutes ago, Geoff Barnes said:

Hi starhopper13, It takes the spot about 4 hours to transit across the face of Jupiter, I think it does a complete orbit in about 9 hours.

It may well have been a shadow transit of one of Jupiter's moons which would cross in an hour or two, especially if it was nearer the top corners when you saw it, the Great Red Spot sits nearer the equator of the planet.

Thanks for the reply, Barnes! I doubt it was a shadow because the moons were quite far off to be casting shadows. The spot was just above the lighter band (inverted view), where I saw it to be in pictures. Also I checked using the tool of sky and telescope that the moons were not casting shadows on the planet at that time. 

Perhaps it really was my eyes playing tricks? 

[starhopper13]

14 minutes ago, Stu said:

@starhopper13 what time were you observing? I see you are in Bangladesh but we can check to see what it was you are likely to have seen.

The first observation was at 10:00pm local time. I think that's 16:00 UT. The second observation was done after 11:00pm local time. 

Is there any tool to see when the GRS is visible? That would be helpful 😁

[Geoff Barnes]

3 minutes ago, starhopper13 said:

Is there any tool to see when the GRS is visible? That would be helpful

Have a play with this one starhopper13.....https://shallowsky.com/jupiter/

[starhopper13]

10 minutes ago, Geoff Barnes said:

Have a play with this one starhopper13.....https://shallowsky.com/jupiter/

Seems like the first spotting of the GRS might've been correct. What I saw later was probably wrong. Thanks a lot for the tool, Barnes. It's really helpful. 

[Stu]

I think these two are correct for 10pm and 11pm local time in Dhaka.

GRS certainly visible in the first instance, likely to have been difficult on the second  and not where you described it so perhaps there was another feature such as a festoon visible?

[starhopper13]

Oh boy!

Excuse my ignorance but this is the first time I've heard of festoons on Jupiter! I'm not sure if I saw one of those, but that's definitely something to look for next time. Thank you so much, Stu!

[Stu]

These two images may help you to understand the different features visible on Jupiter. You won't see detail as vividly as this, but with a good scope and good conditions can certainly pick out these features.

The last image is a pretty bad quality image taken with a smartphone through a very good quality 4" scope when Jupiter was higher in the sky. The actual view through the eyepiece was much sharper and showed more fine detail. You can, however, see a shadow transit and quite a bit of detail in the belts. If you look closely you can see a moon just appearing from behind Jupiter too.

 

[starhopper13]

I guess I'm not done looking at Jupiter just yet 😄

[Stu]

1 hour ago, starhopper13 said:

I guess I'm not done looking at Jupiter just yet 😄

That's what I love about it, it is always changing and there is often something interesting to see.

[Marvin Jenkins]

If your done looking at Jupiter.... Your done, full stop.