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What is causing this light circle?

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#1 amdizack

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Posted 14 November 2012 - 07:19 PM

This might be a dumb question, but can anyone tell me what is causing my data to have a circle of light? This is a stacked image of 32 subs and I know is isn't a processing error. I think it's a capturing error but I can't seem to figure out what I'm doing wrong.
I am using a Celestron 8SE and Nikon with 1.25" t-ring adaptor.

Thanks!

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#2 mmalik

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Posted 14 November 2012 - 07:53 PM

Have you seen this before or is it the first time you have encountered it? Trying to see if some recent change may have caused it.

#3 HeyJP

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Posted 14 November 2012 - 07:59 PM

It looks like vignetting to me. The light coverage is falling off outside of the "circle of light" and only a few very bright stars are making it through. The light cone from your scope is a circle. And your Nikon CCD is a rectangle and for your configuration, the rectangle is bigger than the cone. Virtually no light hitting outside the circular area.

Jim

#4 Charlie B

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Posted 14 November 2012 - 08:01 PM

I'll second vignetting. You may want to go to a 2 inch adapter.

Charlie B

#5 guyroch

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Posted 15 November 2012 - 01:06 AM

Yep, vignetting.

If you take flats and use them in your processing you should be able to reduce it quite a bit.

Guylain

#6 TxStars

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Posted 15 November 2012 - 06:42 AM

That is from the 1 1/4" T-adapter.
Instead you should be using this:
http://www.celestron...-1-4-11-14.html

#7 Jmel

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Posted 15 November 2012 - 09:42 AM

Quite honestly, I use an SCT adapter and I still get vignetting like that. I get it worse with the 1.25 inch adapter when using a star diagonal.

#8 nebultick

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Posted 15 November 2012 - 07:16 PM

what camera is it? the sensor is too big for the size hole the light is going through so you get vignetting. Get a bigger camera adapter or a camera with a smaller sensor. do you happen to have a full frame nikon camera?

#9 Jmel

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Posted 16 November 2012 - 10:43 AM

I am using a Canon EOS Rebel XS 1000D. I am using the celestron sct to dslr adapter, on a celestron 5se.

#10 TxStars

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Posted 16 November 2012 - 11:54 AM

Jmel,
The 5" you have does not have as large of a light cone as the 8" of the original poster and thus will have more of a problem.

#11 amdizack

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Posted 18 November 2012 - 11:54 AM

I'm using a Nikon D5000 with the 1.25" t adapter, no diagonal.

I just ordered the Celestron 2" adapter and hoping that helps.

#12 ToxMan

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Posted 19 November 2012 - 07:47 PM

To make the light cone large enough to cover the sensor, do you have to move the sensor further "out"? Like use an extension tube? I have the same vignetting problem when I attach my micro-Four Thirds camera to my 90mm mak-cass. So, I was trying to decide which direction to go.






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