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Old 15-05-2021, 09:57 PM
Greggles (Gregory)
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Is this vignetting normal?

Hi all,

I photograph with a Nikon D5500 connected to a 10" F5 dobsonian on a DIY EQ platform. Recently i changed the bolts to move my primary mirror up the tube in order to achieve focus with my DSLR with out using a 1.5 barlow.

After doing this i feel like the vignetting has been a lot worse when stretching the image but i'm unable to compare to my old images as they are on a HDD in storage at the moment.

Can moving the mirror up cause more vignetting? or does the 1.5 barlow crop out some of the vignetting?

below is a link to an unedited stack (sequator) and a a single light frame. Just wondering if this seems nomral or excessive after the stack is stretched?

https://drive.google.com/drive/folde...IH?usp=sharing

Thanks Every one,

Greg
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Old 15-05-2021, 10:54 PM
Greggles (Gregory)
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thanks for the reply Glen. ill probably just have to live with it for now which sucks.

Really struggling to get a final image with the stacked image below. If any one wants to have a go at it, feel free.
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Old 16-05-2021, 09:52 AM
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Nikolas (Nik)
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I had a play with it in photoshop, the vignetting is normal but if you take flats that can be calibrated out
I used Gradient exterminator in photoshop which did a great job on the vignetting. The rest was just a quick process, you need a coma corrector which may help
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Old 16-05-2021, 10:25 AM
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+1. Flats are your friend
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Old 16-05-2021, 11:35 AM
Greggles (Gregory)
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Wow, Quick process? this looks great. I guess I need a lot of improvement on my post processing with photoshop!

Flats, Noted.. Might run out today and grab and artists tracing light board to take flats. seems like one of the easiest methods.

Regards,

Greg


Quote:
Originally Posted by Nikolas View Post
I had a play with it in photoshop, the vignetting is normal but if you take flats that can be calibrated out
I used Gradient exterminator in photoshop which did a great job on the vignetting. The rest was just a quick process, you need a coma corrector which may help
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Old 16-05-2021, 04:43 PM
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Nikolas (Nik)
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Quote:
Originally Posted by Greggles View Post
Wow, Quick process? this looks great. I guess I need a lot of improvement on my post processing with photoshop!

Flats, Noted.. Might run out today and grab and artists tracing light board to take flats. seems like one of the easiest methods.

Regards,

Greg
Quick process ie colour balance and chroma noise reduction after some stretching
you had some good data there
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Old 16-05-2021, 10:14 PM
Greggles (Gregory)
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Thanks Mate,

Although i feel like an idiot... I just used flats for the first time... why on earth did I wait so long to use flats! the results where awesome and editing is so much easier when not having to deal with the gradient! :O

Quote:
Originally Posted by Nikolas View Post
Quick process ie colour balance and chroma noise reduction after some stretching
you had some good data there
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