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Old 16-04-2018, 03:06 PM
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Whirlpool with 80 mm

Following Peters advice I considered stacking only 30 frames but as I had 129 I thought no I will stack 95% of them which is approximately 30

So the sky was better than perfect so I moved closer than usual to the stars probably 20 feet from the house and captured 129 30 second frames thru my 80 mm Skywhatcher triplet scope riding upon a HEQ 5 Equatorial mount that despite hours of attention did not seem to become correctly polar aligned.

I suspect the mount may be slowly sinking upon the cement pavers I placed to prevent such an event.

The polar align is still out and I cant figure it out and looking at the individual frames they show longish stars but the stack seems to have fixed it a little..how that works I do not know.

Put them in Deep Sky Stacker ( a free software that allows combination of multiple frames into one image) together with 12 dark frames (photos taken with the lens cap on to reveal any non performing pixels) and 18 flat frames (short exposures with a white sheet over the front of the scope designed to show up any unwanted objects in the optical path such as dust on the lens) and 13 bias frames ( taken at a fast shutter speed with the lens cap on to do what I am not entirely sure).

After many hours a final image was worked upon using gimp (a free program to further process an image).

The bottom of the first short was cropped away because it had major problems probably as a result of my large baffeled dew tube moving to obstruct the light coming to the lens at some point during capture...maybe..

The second image is a major crop to see what detail I could get in the galaxy.

Alex
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Old 16-04-2018, 03:14 PM
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Very nice, Alex
There is almost no noise (thanks for 129 frames) but I can see some astigmatism (stars are sort of sligtly rectangular).
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Old 16-04-2018, 03:35 PM
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Quote:
Originally Posted by bojan View Post
Very nice, Alex
There is almost no noise (thanks for 129 frames) but I can see some astigmatism (stars are sort of sligtly rectangular).
Thanks Bojan.
You refer to the stars in the second image no doubt?
That comes from trying to make the stars smaller in gimp using "errode" which I guess is a poor mans deconvolution...still to get pixinsite but as I was not getting any captures I have put it off...I had a trial version but have yet to pay up for a licience.
Been busy so its down the to do list.
Alex
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Old 16-04-2018, 03:37 PM
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Aaaa, that's what it is..

Do you use Canon camera?
DPP can do a good postprocessing job.. you can use 16-bit TIFF file (after saving from DSS) to do curves, stretching etc.
See here.
I wrote about the method long time ago in this forum.. will look for the post later....

EDIT:
here it is:
http://www.iceinspace.com.au/forum/a...se.php?a=62092
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Old 16-04-2018, 04:00 PM
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Hi Bojan
I switched camps and went to nikon.
Thinking more about the star shape and looking at various frames I feel it may come down more to polar alignment.
I could not get phd to work yet so resorted to the 30 second cop out.
Alex
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Old 16-04-2018, 04:05 PM
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I dont use goto so I was happy to find it...which you can do under dark sky..I spotted it first with 80 mm binos (and what a excellent view of everything they provided) and then in the finder scope.
Same with hamburger which I have yet to process...but been told to get off the computer...and when all go to bed forget the computer I will be back outside.
Alex
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Old 16-04-2018, 06:48 PM
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Quote:
Originally Posted by xelasnave View Post
Thanks Bojan.
You refer to the stars in the second image no doubt?
That comes from trying to make the stars smaller in gimp using "errode" which I guess is a poor mans deconvolution...still to get pixinsite but as I was not getting any captures I have put it off...I had a trial version but have yet to pay up for a licience.
Been busy so its down the to do list.
Alex
You get the same effect using a noise radius of 2 in ImageMagick.
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Old 17-04-2018, 09:56 AM
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You get the same effect using a noise radius of 2 in ImageMagick.
Thanks for the tip.
Alex
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Old 18-04-2018, 02:19 PM
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Hay Alex, missed this one!

Unreal mate
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Old 18-04-2018, 04:55 PM
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Thanks Peter.
Poor PA, 30 second exposure and a mug at the wheel ...just shows the importance of a dark location☺...but the little 80 mm has surprised me ...I love it.
Alex
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