13 replies to this topic

[nirvanix]

I'm posting this as there's always lots of discussion and wonder on the CN reflector forum as to whether or not a person's dob is performing as it should. I thought I'd share what I see so other's might get a better idea about their own scope.

The picture below is an accurate representation of what Jupiter looks like in my 10" reflector when it's ABOVE 30 degrees elevation and the seeing is very good (P 8 -10).

 

Things to notice are the blue festoons in the EZ, detail in the cloud bands and the GRS, and some barely discernable white ovals in the far north and south regions.

 

I would say my scope is at least diffraction limited from the testing I have done, and I always keep it precisely collimated and cooled to ambient before use. Needless to say, I'm looking forward to Jupiter climbing up above 30 degrees elevation from my locale. It's been a long time.

 

[Barlowbill]

Very nice pic.  I wish I could see that in my 8".  Thanks

[Pokemoncrusher1]

What magnification is this at? also im jealous of your seeing, I haven't had above poor seeing for almost 4 months now! 

[DAG792]

The image and the detail visible is very accurate, however for better representation of what you see, you might wanna shrink Jupiter by an order of magnitude.

[Echolight]

Interesting. I guess because of the great seeing that diffraction spikes have nothing to reflect on. I think this may be true with my achromat also, as there are times when the halo from CA seems invisible while other times it is more prevalent.

[ngc7319_20]

That looks like a good representation of what is visible in better than average seeing conditions, and better than average optics.  That said, there is still an enormous amount of additional detail that can be seen with Jupiter overhead in perfect seeing, and excellent optics.  I think these sorts of tests are strongly affected by the seeing, which will limit their usefulness.

 

This is what I suggest would be visible in an 11" Dob with Jupiter near zenith, near perfect seeing, very stable temperatures, excellent optics, and smallish diagonal mirror.

 

Edited by ngc7319_20, 28 February 2021 - 01:43 AM.

[JKowtko]

Is this really what you see through the eyepiece?  If so, can you take a pic through the eyepiece with your phone and post it?  

 

What equipment are you using (ep, barlow, filter)?

 

If I could get anywhere remotely close to your photo with my Dob I would be ecstatic ... the best of what I have seen so far was in Dec during the Conjunction, granted much lower on the horizon for me ... but looked more like this:

 

 

Thanks.  John

[DAG792]

Is this really what you see through the eyepiece?  If so, can you take a pic through the eyepiece with your phone and post it?  

 

What equipment are you using (ep, barlow, filter)?

 

If I could get anywhere remotely close to your photo with my Dob I would be ecstatic ... the best of what I have seen so far was in Dec during the Conjunction, granted much lower on the horizon for me ... but looked more like this:

 

Screen Shot 2021-02-28 at 6.18.06 AM.png

 

Thanks.  John

Most probably the issue you're having is poor seeing. Besides, a one-off pic wouldn't be able to capture all the detail you can see at the eyepiece. I can assure you, an 8 inch Dobsonian can reveal far more than your photo. I can see more detail with a 4 inch scope than the detail in your photo. It's not a problem with the scope, but rather its a problem with the atmosphere. Jupiter is very low, and atmospheric dispersion plays havoc on the low contrast detail.

When everything is perfect... Your scope is collimated, cooled, the seeing is great, Jupiter is at opposition and so on, I can assure you, the view through even a modest scope is awe-inspiring.

[Spikey131]

With a 12.5” f/7 Newtonian and binoviewers, on a night of good seeing here in the northeast USA, I can get views similar to post #1.  Granted, visual observation and stacked video frames are two different things.  Planetary observation requires time at the eyepiece, watching crisp views of details coming and going with fluctuations of atmospheric interference.  But I think the photo in post #1 is a fair representation.  
 

So if you are only ever getting views like post #7, there is room for improvement.  Maybe your scope needs collimation or proper cooling.  Of course, if the seeing is poor or the planet is low in the sky, that may be all you get.  But even though 2020 wasn’t the best apparition of the gas giants, I got some pretty good nights, with views more like post #1.

 

I have never seen Jupiter look like post #6, although some of the details depicted in the photo might be seen intermittently with prolonged viewing.  But I have never observed the planets with large aperture from the tropics, so maybe such images are possible at the eyepiece.

[ngc7319_20]

I have never seen Jupiter look like post #6, although some of the details depicted in the photo might be seen intermittently with prolonged viewing.  But I have never observed the planets with large aperture from the tropics, so maybe such images are possible at the eyepiece.

Yes, post #6 is my impression of eyepiece view from Florida Keys (Winter Star Party) couple years back on superb night w 11" F/5.4 Zambuto equipped Dob.  Little disk of Io was visible w/ details transiting across details in Jupiter cloud bands.  It was just amazing view.  Optics were pre-cooled to night time temperature. It was dramatic and revealing how much seeing, atmosphere, thermal stuff, etc., get in the way the rest of the time.  So when someone asks "does the view in my scope look right?" I think the seeing / atmosphere is the big elephant in the room.

[stargazer193857]

I bet those are time averaged photos. Maybe stacks of the best. Photography can see so much that the eye misses.

[SteveG]

I'm posting this as there's always lots of discussion and wonder on the CN reflector forum as to whether or not a person's dob is performing as it should. I thought I'd share what I see so other's might get a better idea about their own scope.

The picture below is an accurate representation of what Jupiter looks like in my 10" reflector when it's ABOVE 30 degrees elevation and the seeing is very good (P 8 -10).

 

Things to notice are the blue festoons in the EZ, detail in the cloud bands and the GRS, and some barely discernable white ovals in the far north and south regions.

 

I would say my scope is at least diffraction limited from the testing I have done, and I always keep it precisely collimated and cooled to ambient before use. Needless to say, I'm looking forward to Jupiter climbing up above 30 degrees elevation from my locale. It's been a long time.

 

jupiter.jpg

That is a good representation of what I see with my 10" dob on a very good night. I agree that you are at least at "diffraction limited".

[niallk]

I've seen views like the OP's Post in my SW 10" dob, on very very good nights - everything cooled to equilibrium and collimation. I've seen views somewhat approaching the pic in post #6 in my 15" on an excellent night.
I've had many many nights where I see mush. Ireland is often under the jetstream, and Jupiter hasn't been at decent altitudes from here for a while!!! Takes patience to get everything to come together, but when it does, the views get burned into memory

[nirvanix]

What magnification is this at? also im jealous of your seeing, I haven't had above poor seeing for almost 4 months now! 

Thanks for your question. On very good nights of seeing I'll use between 250 - 400x magnification. Sadly, those nights don't come around too often where I am. Typical seeing is about P 4, so mediocre. That's when I have to keep mag down to 100 - 150x.