Author Topic: Dark smudge on DBE image  (Read 1037 times)

Offline John_Gill

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Dark smudge on DBE image
« on: 2017 November 29 04:34:24 »
Hi,

I got some "great" images of the Flame Nebula last night with my DSLR at ISO 100 for 900 seconds.  I was using a focal reducer on an 8" EdgeHD scope.  After pre-processing I now find a dirty black mark in the middle of the Flame  :yell:  I guess I had some muck on the focal-reducer.  When I zoom in on the lights I can see the flaw very faintly.  So do I try and clone-stamp the lights or try and fix the issue during the post-processing?

Look up (and clean the focal-reducer),
John
APM 107/700 apo on CGX mount
ZWO Optics - Autoguiding
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Offline ngc1535

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Re: Dark smudge on DBE image
« Reply #1 on: 2017 December 01 12:37:17 »
Hi John,

If your data is dithered (well) and the smudge is not present in all frames in the same place (and you have enough images)- you can use my Selective Rejection technique.

https://pixinsight.com/forum/index.php?topic=11609.msg71757#msg71757

No, you shouldn't need to clone anything. In fact... if you cannot use the technique above with the data you have in hand, all you need to do is take more images of the object. This will not only get you better S/N but also permit you to use your first set of data without penalty (and cloning).

-adam
« Last Edit: 2017 December 01 12:53:01 by ngc1535 »

Offline pscammp

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Re: Dark smudge on DBE image
« Reply #2 on: 2017 December 03 04:15:25 »
John,
    Did you take Flats ?

Could be a dust bunny which Flats should take out completely

Paul

Offline John_Gill

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Re: Dark smudge on DBE image
« Reply #3 on: 2017 December 06 22:38:46 »
Hi,

Sadly all the images were assigned to the rubbish bin and filed under the heading "make sure optics are clean before use"  I had used flats but they were unable to fix the smudge.  The problem was that there was some mildew on the focal reducer. 

So here is my astrophotography tip # 35.  If you live in a tropical area and dampness is an issue, then every couple of months place optics in direct sunlight.  Any mildew will be killed off by sunlight.

Look up
John
APM 107/700 apo on CGX mount
ZWO Optics - Autoguiding
ZWO1600mm and filters
... when there are no clouds ...

Offline ngc1535

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Re: Dark smudge on DBE image
« Reply #4 on: 2017 December 08 15:07:58 »
John,

Whining about Mildew eh? Be glad Mothra doesn't show up in your images:



I hope to demonstrate how to use this otherwise perfectly good image and *not* throw away in the "rubbish bin."

-adam

Offline jkmorse

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Re: Dark smudge on DBE image
« Reply #5 on: 2017 December 08 15:35:29 »
Adam,

Where is Godzilla when you need him?   :)

Jim
Really, are clear skies, low wind and no moon that much to ask for? 

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Offline John_Gill

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Re: Dark smudge on DBE image
« Reply #6 on: 2017 December 12 02:55:05 »
erm, I know there is a Butterfly cluster but this is crazy.... hahahahaha
APM 107/700 apo on CGX mount
ZWO Optics - Autoguiding
ZWO1600mm and filters
... when there are no clouds ...