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Hi

The other night I managed to get 22 subs on the horsehead nebula. In my excitement i used DSS and the processed them using gimp. However when the final picture came through there where 2 light streaks quite close to Alnitak.  Is there away of getting rid of those marks using gimp? 

No other streaks appear on other sub pic i have taken  :confused1:

Iam using a 450d canon camera and a astronomik cls filter. With a celestron 8" SCT on a avx mount 

Thanks

Dean

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As above, difficult to say without an image to look at. A steady hand with the clone tool if there is one in Gimp.

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Looks like an internal reflection in the imaging OTA somewhere, Alnitak is very bright!

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I'd go with John as a reflection somewhere. Alnitak is an awfully bright star..... I bet its caused no end of issues, it certainly has me.... With reflections :)

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Seems odd that you're getting a diffraction spike on the brighter star to the right too - yet you're using an SCT which should be devoid of any spikes. I suggest checking your optics for obstructions or any bits on the lenses.

ChrisH

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Thanks for the feedback everyone. It does seem strange. I took a picture of M35 earlier that night but no streaks that i can see. I have only used compressed air to blow over the corrector plate. I havent cleaned it at all. I got the scope in march

post-46757-0-59103500-1452455875_thumb.p

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Thanks for the feedback everyone. It does seem strange. I took a picture of M35 earlier that night but no streaks that i can see. I have only used compressed air to blow over the corrector plate. I havent cleaned it at all. I got the scope in march

Stars are not bright enough in that image, likely you wouldn't get diffraction spikes on that even with a Newt :-)

ChrisH

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I don't think there is anything odd going on here. Alnitak is a bright devil. I've imaged this area in all sorts of scopes from 66mm to 355mm. Most optical systems will throw up optical challenges when Alnitak is in view. I wouldn't bust a gut trying to work out just what is happening. Your best bet is to try recentering the target to see if you can catch it without those artefacts. You then use layers to see if you can patch the bad bits. In my experiece the antidote to Alnitak comes in the form of the TEC140, which seems to be impervious to it! (An expensive solution!)

Olly

Edited by ollypenrice
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Need to buy  a lotto ticket  :laugh:  :laugh:  :laugh: Will try again with the Horsehead nebula buy reentering the target. 

Olly  mentioned about layers, is it possible to give me a quick overview how to do this, or point me to a good link? 

Thanks

Dean

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Need to buy  a lotto ticket  :laugh:  :laugh:  :laugh: Will try again with the Horsehead nebula buy reentering the target. 

Olly  mentioned about layers, is it possible to give me a quick overview how to do this, or point me to a good link? 

Thanks

Dean

I can't say it will work but flares and reflections are often worse off axis. If you can find a framing which doesn't produce them then you do a shoot, process it and save it as a layer. (It needs to be co-registered to the original. I use Registar.) You can then put the clean image as a bottom layer and erase the top one where it has artefacts. You don't need the same strength of signal on the 'fix' layer because you'll only be using a tiny part of it.

Olly

Edited by ollypenrice
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Are you using a reducer? I ask because the Celestron .63 reducer causes exactly this type of horrible reflection all around the edges on even average brightness point sources.

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Yes i am using a reducer. Do you use yours without a reducer. However never noticed it before not even with the orion nebula. 

Olly will give the layers ago. However i think with all these things  may take a while to get my head round it!

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I have a similar image of The Horsehead taken a few nights ago.


8" F6.3 (native not reducer) Meade SCT, modified Canon EOS 450D.


My camera was rotated 90 degrees with the short side north, with Alnitak right on the edge of the short side, as in gonzo's image.


The stacked and the stretched result has multiple faint spikes (about 30) out to about 5 diameters of Alnitak , as can faintly be seen in gonzo's image, and on all my other stars to a much lesser degree.


But no devil's horns, or the two pronounced spikes on the star to right of frame.


Maybe one of the small sticky-out bits at top-left in the Canon throat, which would normally be a bit vignetted and not highly illuminated?


My image train is Meade microfocuser and 450D only.


Michael

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