Uranus and it's moo...
 
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Uranus and it's moons

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Paul Walker
(@pwalker)
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Last night 11-20-2022, I tracked down and viewed Neptune and Uranus. Neptune is 7.8 magnitude and appears ~2" across, barely bigger than Jupiter's largest moon Ganymede (1.7"). It take high magnification to discern it as a disk. Though 200x is enough in good seeing, maybe less for an experienced observer, 300x or more is better, if your telescope is big enough. It has a moon, Triton, that is bright enough at 13.5 magnitude to see in medium sized telescopes (10" or larger is best but on a good night an 8" might be big enough. Last night using my 10" f/5.6 with the binoviewers at 282x I was not able to detect it even though it was well placed away from the Neptune. At ~4" across Uranus is much easier to discern as a disk. If the seeing had been better I might have been able to see one or more of it's moons but they are faint and never get far from their parent planet.

I did not try imaging Neptune but I did image Uranus. May got a little bit of cloud detail. I also took several 10 sec exposures to try to get some of the moons. We are currently looking a "down" on the north pole or "up" on the south pole so the moons appear to be doing circles around Uranus. Based on their movement in Starry Night Pro planetarium software, it is the south pole.

Paul

From video clip:
10" f/5.6 Newtonian, Canon T7i camera, eyepiece projection using a 15mm eyepiece, 3x digital zoom, stack of 1000 frames from a 5,414 frame (3 minute) video clip, 1/30 sec @ ISO 6400.
Converted from MPG4 to AVI format using PIPP, stacked using Stakkert!3, post processed in Registax 6 (wavelets, histrogram stretch, RGB align).
We are looking at the south pole of Uranus. There is definitely some distortion which may at least in part be from the diffraction spikes from the spider vanes holding the secondary mirror.
The image field of view (side to side) is same you would see if observing at about 1200x using an eyepiece with a 60 degree apparent field of view.

 
Detail or just noise? Can't really say without a confirming image. Maybe a dark area or areas centered on the pole and a bright cloud at the 4:30 position?
 
From still shots:
10" f/5.6 Newtonian, Canon T7i camera, eyepiece projection using a 15mm eyepiece, stack of 11 shots, 10 sec @ ISO 6400 with a 1/6 sec @ ISO 6400 cloned in to replace the overexposed image of Uranus.

Magnitude of Uranus's moons:
Oberon 14.05
Umbriel 14.95
Titania 13.84
Ariel 14.28
Miranda 16.42 not visible, to faint and too close to Uranus

See next image for identifying the moons.

 
Moon locations and magnitude of field stars.
This topic was modified 5 days ago 3 times by Paul Walker

   
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Terri Zittritsch
(@terri)
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Joined: 3 years ago
Posts: 165
 

Paul, cool capture with the moons.      I've not pointed the scope that direction very much this year.  I think I've looked at her once just visually.     Maybe while waiting for Mars I can get a glimpse tonight.     Can you see any of the moons visually or are they just too dim?


   
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Greg Erianne
(@greg-erianne)
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Joined: 1 year ago
Posts: 94
 

Sorry, I missed these!  Nice capture of this tiny target, Paul!  I'm amazed you can get this much, to be honest.  Do you think the digital zoom on the camera may be distorting the image a little bit?  The only camera digital zoom I've ever used was on the iPhone and I know it distorts things slightly.  Wasn't sure if that was the case with your T7i, especially with all the other magnification in the imaging train, although I'm aware that the digital zoom on the T7i is very good and much better than a mobile phone's digital zoom.

I'm also amazed you were able to image with all the wind we've had.  That's quite something.

Excellent captures, Paul!

Greg


   
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Paul Walker
(@pwalker)
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Joined: 10 years ago
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Thanks. The last time (the only other time) I imaged them was in November 2008.  I took about 100 still shots (used about 70 each planet) at that time and used the afocal method with a point & shoot camera on the same 10" f/5.6 scope.

Yes, it was windy on the 20th, but this scope is not much bothered by wind.  I was more bothered by the wind than the scope.  But I did reduce the wind by putting up one of my wind & light blocking tarps plus used the shed doors to block the spaces between the roll-off sheds.

The digital zoom on the T7i doesn't seem to cause distortion.  In video mode the camera normally shoots a 1x only, but you can put it in zoom mode where you get 3x to 10x digital zoom range.  Based on experimenting during the daytime it appears that at 3x zoom the camera is doing an "area of interest" which means one is not losing resolution but actually using the full or close to full resolution of the middle of the sensor.  The sensor is 6000x3000 pixels.  I don't know if at 3x zoom is it taking 2000 of middle 6000 pixels and resizing them to the 1920 px resolution of the HD video or is taking only 1920 pixels resulting in 3.125x.


   
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Greg Erianne
(@greg-erianne)
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Joined: 1 year ago
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Posted by: @pwalker

Thanks. The last time (the only other time) I imaged them was in November 2008.  I took about 100 still shots (used about 70 each planet) at that time and used the afocal method with a point & shoot camera on the same 10" f/5.6 scope.

Yes, it was windy on the 20th, but this scope is not much bothered by wind.  I was more bothered by the wind than the scope.  But I did reduce the wind by putting up one of my wind & light blocking tarps plus used the shed doors to block the spaces between the roll-off sheds.

The digital zoom on the T7i doesn't seem to cause distortion.  In video mode the camera normally shoots a 1x only, but you can put it in zoom mode where you get 3x to 10x digital zoom range.  Based on experimenting during the daytime it appears that at 3x zoom the camera is doing an "area of interest" which means one is not losing resolution but actually using the full or close to full resolution of the middle of the sensor.  The sensor is 6000x3000 pixels.  I don't know if at 3x zoom is it taking 2000 of middle 6000 pixels and resizing them to the 1920 px resolution of the HD video or is taking only 1920 pixels resulting in 3.125x.

I have 3-10x zoom on my SL3 in video mode as well -- which I didn't even know until I got curious after your post!  I'll have to give it a try next time I'm imaging a planet or the moon!  Of course, the SL3 is not as good a camera as your T7i, but I'll give it a 'shot'.  😀 

Greg

 

 


   
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