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  #41  
Old 09-05-2018, 07:12 AM
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gregbradley
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Gee whiz I think this discussion has gone off the rails a bit. Sombrero is a small galaxy, the elliptical is large but the spiral is 1/3rd the size of the Milky Way. So your image is not "soft". You've gotten depth, great colour with very low noise and a nicely detailed image.

There are techniques like multi layered Decon that can help but as you know and many have commented, heavy sharpening techniques don't come free. There is usually some damage. I think the best processing choice is to keep it looking natural, do some sharpening/contrast improvement just before it becomes noticeable and then that's the limit.

So don't falsely conclude you should only do faint objects as this is a stand out image. As you say longer focal length scopes are heavily affected by seeing. I just did some more time on the Sombrero myself over the weekend to add to mine. It was softer than the original data which was taken on better seeing nights. Seeing wasn't bad just not as good.

On my CDK17 I have had seeing affect it so much that when the seeing was bad I could not even focus the scope as it would go in and out of "focus" even when I had not changed the focus at all.

Greg.
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  #42  
Old 09-05-2018, 09:45 AM
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Ryderscope (Rodney)
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This is a stunning image MnT. The original version has my vote as it presents the data and the image “as it is” resulting in a beautiful galaxy that looks to be floating in space (which it is of course).
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  #43  
Old 09-05-2018, 11:02 AM
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Quote:
Originally Posted by Placidus View Post
In the attached, we bravely compare with seven other utterly superb images by leaders in the field using excellent (but widely differing) technology under similar circumstances.
Thanks for the analysis and explanation, Mike! I just happen to have some data on the Sombrero myself and it will be interesting to compare when I finally get around to processing it.

FYI, Martin Pugh is using an AOX on his CDK17 at Yass and getting remarkably small FWHMs on good nights.

Cheers,
Rick.
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  #44  
Old 09-05-2018, 05:03 PM
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PKay (Peter)
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Now my monthly background image.

As an aside, I have kept an image taken by that telescope that orbits our planet. You have matched that, and more...

Thank You MnT.
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  #45  
Old 09-05-2018, 06:14 PM
Placidus (Mike and Trish)
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Thanks muchly, colleagues. We've been out shopping for treated pine, yoghurt starter, and other goodly things.

Quote:
Originally Posted by Gnat View Post
I just projected your photo on the big screen TV. Had a ball finding the galaxies captured in your photo and zooming in on the dust lanes and the stars on the right in the spiral arms. Great capture.
Cheers, Natalie, that's kind. Love the nickname.

Quote:
Originally Posted by PRejto View Post
Mike,

With your brains I think you could "easily" build your own AO along the lines of the SX-AO. It's just a thick clear window with 4 motors controlling tilt. It can be placed just about anywhere in the system...even quite far away from the CCD and it can use any guide camera.

Peter
Spent much of the day thinking about that. We control the RA and Dec motors at 2250 Hz, so 10 Hz sounds easy! Ahem. How hard can it be, as they say on Top Gear.

Quote:
Originally Posted by topheart View Post
Hi Mike,
Interesting discussion and comparison. I think you are doing great as you are and it is so much work and expense to swap everything out....so assessing the benefit would need to be done very carefully....maybe I can formally assess the difference with and without the AO-X for you on a few typical nights, perhaps when the full moon is interfering with serious imaging....let's see if I can setup a scientific comparison. Also, I forgot to mention I have a 0.6 reducer in the light path to the off axis guider, so the FOV of the guider is a bit bigger and the stars a bit brighter....so the OAG sees 0.6 of the 4.7M focal length of the main scope.

Cheers,
Tim
Thanks for a very thoughtful comment, Tim. It would be truly wonderful, as a thing in its own right, to make use of a full moon evening and do a set of say 10 alternating subs with and without AO. Many would love to see the result.

Quote:
Originally Posted by gregbradley View Post
Gee whiz I think this discussion has gone off the rails a bit. Sombrero is a small galaxy, the elliptical is large but the spiral is 1/3rd the size of the Milky Way. So your image is not "soft". You've gotten depth, great colour with very low noise and a nicely detailed image.

There are techniques like multi layered Decon that can help but as you know and many have commented, heavy sharpening techniques don't come free. There is usually some damage. I think the best processing choice is to keep it looking natural, do some sharpening/contrast improvement just before it becomes noticeable and then that's the limit.

So don't falsely conclude you should only do faint objects as this is a stand out image. As you say longer focal length scopes are heavily affected by seeing. I just did some more time on the Sombrero myself over the weekend to add to mine. It was softer than the original data which was taken on better seeing nights. Seeing wasn't bad just not as good.

On my CDK17 I have had seeing affect it so much that when the seeing was bad I could not even focus the scope as it would go in and out of "focus" even when I had not changed the focus at all.

Greg.
Thanks very much for that, Greg. You've steadied the horses a bit.

Quote:
Originally Posted by Ryderscope View Post
This is a stunning image MnT. The original version has my vote as it presents the data and the image “as it is” resulting in a beautiful galaxy that looks to be floating in space (which it is of course).
Hi, Rodney! Thanks for the cheery vote of confidence in the gentle approach.

Quote:
Originally Posted by RickS View Post
Thanks for the analysis and explanation, Mike! I just happen to have some data on the Sombrero myself and it will be interesting to compare when I finally get around to processing it.

FYI, Martin Pugh is using an AOX on his CDK17 at Yass and getting remarkably small FWHMs on good nights.

Cheers,
Rick.
Ta, Rick. I should write to Martin and ask about his set-up.

Quote:
Originally Posted by PKay View Post
Now my monthly background image.

As an aside, I have kept an image taken by that telescope that orbits our planet. You have matched that, and more...

Thank You MnT.
Thanks, Peter. That's very encouraging.

Very best,
Mike and Trish
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  #46  
Old 09-05-2018, 07:36 PM
topheart
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Quote:
Originally Posted by Placidus View Post

Thanks for a very thoughtful comment, Tim. It would be truly wonderful, as a thing in its own right, to make use of a full moon evening and do a set of say 10 alternating subs with and without AO. Many would love to see the result.


Mike and Trish
No worries....as long as I have a bit of free time around the full moon, then I will give it a go.
Cheers,
Tim
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