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Astrophotography and Sketching >> DSLR & Digital Camera Astro Imaging & Processing

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amdizack
member


Reged: 08/23/12

Loc: Goodyear, AZ
What is causing this light circle? new
      #5520015 - 11/14/12 07:19 PM Attachment (47 downloads)

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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mmalik
Postmaster
*****

Reged: 01/13/12

Loc: USA
Re: What is causing this light circle? new [Re: amdizack]
      #5520054 - 11/14/12 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.

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HeyJP
professor emeritus


Reged: 12/11/10

Loc: Boulder, CO
Re: What is causing this light circle? new [Re: mmalik]
      #5520061 - 11/14/12 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


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Charlie B
scholastic sledgehammer


Reged: 03/22/08

Loc: Sterling, Virginia
Re: What is causing this light circle? [Re: HeyJP]
      #5520068 - 11/14/12 08:01 PM

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

Charlie B


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guyroch
Vendor (BackyardEOS)
*****

Reged: 01/22/08

Loc: Under the clouds!
Re: What is causing this light circle? new [Re: Charlie B]
      #5520439 - 11/15/12 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


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TxStars
Pooh-Bah
*****

Reged: 10/01/05

Loc: Lost In Space
Re: What is causing this light circle? new [Re: amdizack]
      #5520630 - 11/15/12 06:42 AM

That is from the 1 1/4" T-adapter.
Instead you should be using this:
http://www.celestron.com/astronomy/celestron-t-adapter-c5-6-8-9-1-4-11-14.html


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Jmel
member


Reged: 01/24/12

Loc: Eastern North Carolina
Re: What is causing this light circle? new [Re: TxStars]
      #5520820 - 11/15/12 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.

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nebultick
member
*****

Reged: 10/09/12

Re: What is causing this light circle? new [Re: Jmel]
      #5521757 - 11/15/12 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?

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Jmel
member


Reged: 01/24/12

Loc: Eastern North Carolina
Re: What is causing this light circle? new [Re: nebultick]
      #5522627 - 11/16/12 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.

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TxStars
Pooh-Bah
*****

Reged: 10/01/05

Loc: Lost In Space
Re: What is causing this light circle? new [Re: Jmel]
      #5522776 - 11/16/12 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.


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amdizack
member


Reged: 08/23/12

Loc: Goodyear, AZ
Re: What is causing this light circle? new [Re: nebultick]
      #5525963 - 11/18/12 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.


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ToxMan
Carpal Tunnel
*****

Reged: 01/23/11

Loc: Tucson, Arizona, USA
Re: What is causing this light circle? new [Re: amdizack]
      #5528673 - 11/19/12 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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