Dark smudge on DBE image

[John_Gill]

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    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

[ngc1535]

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

[pscammp]

John,
    Did you take Flats ?

Could be a dust bunny which Flats should take out completely

Paul

[John_Gill]

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

[ngc1535]

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

[jkmorse]

Adam,

Where is Godzilla when you need him?   

Jim

[John_Gill]

erm, I know there is a Butterfly cluster but this is crazy.... hahahahaha