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NGC 7023 The Iris Nebula

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#1 KungFood

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Posted 18 June 2021 - 06:43 PM

Second light for my ASI2600MC. Shot this last weekend in SE Oklahoma, bortle 3 skies. Seeing was pretty darn good. Started off cloudy, but I made the drive anyway. My ritual sacrifices must have worked because the sky cleared right around dusk and stayed lovely all night, then clouded up again just as the sun came up. Guiding was good at .6 - .7", perfectly good at my .97 pixel scale. I'm not happy with the star shapes (or the bit of bloat), but this was the first good night in more than a month and I couldn't bring myself to mess with tilt and backspacing. So crop crop crop and this is the result. I'll get the tilt and spacing worked out, then re-shoot this with more data, 15+ hours would be tasty.
 
Can't tell ya how happy I am with this camera. The raw stack from DSS was really nice with just an autostretch in PI. Not much processing was needed on this. Coming from a DSLR, this camera is a red cylinder of magic!

 

Pixinsight Workflow: 
Color Calib
BG Neut
Slight SCNR
Gentle Deconvolution
MLT Noise reduction (this is where I'm still very unhappy with my results)
----- Histogram Stretch----- ( I experimented with ArcSinStretch but wasn't pleased with the result)
Gentle MLT Sharpen
Curves saturation.
Profit!
 
56x300s RGB
36xdarks
25xdarkflats
25xflats
 
AstroTech AT115EDT
AstroTech .0x flattener
ASI2600MC
Skywatcher EQ6R-Pro
N.I.N.A.
 

 
Iris


Link to Hi-res
https://www.astrobin.../full/o8o8mg/C/

 

 

Clear skies all!

 

 


Edited by KungFood, 18 June 2021 - 06:48 PM.

  • Jim Waters, elmiko, terry59 and 13 others like this

#2 ChrisWhite

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Posted 19 June 2021 - 08:10 AM

Processing and data looks very nice.  Good job!  There seems to be a severe tilt from top to bottom.  It looks like The top is tilted in and the bottom is tilted out.  Curious how your image train looks.  Are you using compression clamps or is it all threaded?  Could the focuser be sagging?



#3 KungFood

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Posted 19 June 2021 - 08:00 PM

Yup, there is significant tilt. I cropped out the worst of the aberration, but no crop will remove it all. I took a stab at sorting it out, the 2600mc does have a tilt adjuster, but i only really made it worse and ended up just leveling the adjuster plate with plans to give it another try another night. Then the sky clouded over for more than a month. I got the demo of CCD Inspector, but it's now run out and I just can't justify it's price for the one function. I''l need to find another way to view tilt issues. I do plan on re-shooting this with for more data (15+ hrs would be nice) after I get the tilt sorted out.

 

Unfortunately, my flattener is not threaded, its currently held in with three screws. I do take care to make sure its all flush on the shoulders before I tighten it down, and then tighten in stages to keep the screws relatively even. I purchased the Astrotech .8x reducer/flattener made for this scope maybe 8 months ago, but still haven't seen it. I'm guessing its only a myth and I was a fool to believe it existed. It does have screw threads on the shoulder, which I'd prefer. I doubt the focuser is sagging, It's quite robust, but don't know how I could check that.


Edited by KungFood, 19 June 2021 - 08:09 PM.


#4 ChrisWhite

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Posted 20 June 2021 - 06:20 AM

You dont need to CCDI to test tilt.  Star testing is by far the most effective way to discover tilt and is the only definitive test. 

 

Regarding focuser sag.  Point to a spot above the horizon to the East and take a 30 second capture.  Then slew to the West and do the same.  Compare images.  Does the tilt remain the same on the image?  If so... the focuser is not sagging.  if the tilt moves to the opposite side of the image, you have focuser sag. 

 

Regarding the compression clamps.  This is likely to be the source of your tilt.  Using the tilt plate to address this is futile if this is the case as every time you move your camera orientation, or re-clamp in place you will nullify any adjustment you have made for tilt.  The tilt is so severe that this really jumps out to me as being the source of your problem.  You can test this by loosening and reclamping a few times and take some images.  Does it change the tilt?  One way to "help" ensure you get a flush mating is to only attach your image train when your scope is pointing at the zenith, or straight down (tough to do with a tripod in the way so maybe when not mounted).  Make sure there is either firm even pressure on the camera and clamp in place.   This is not a fix for the problem though... threaded connections are the gold standard. 

 

I would not fool around with the tilt plate until you resolve these other two potential sources. 



#5 elmiko

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Posted 20 June 2021 - 11:49 AM

Nice image my friend!!



#6 Mert

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Posted 21 June 2021 - 01:01 PM

Very inpressed by the smooth looking dark areas.
That camera really shines!
Good processing.

Edited by Mert, 21 June 2021 - 01:01 PM.



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