Strange noise on images... Could this be dew?

Harry KaramitsosD. Jung
25 replies646 views
Harry Karamitsos avatar
I took some images last night and woke up to some strange noise. My brother thinks it may be dew.  Any ideas?

This is a close up view of the Sii



and the Oiii but less magnified.

D. Jung avatar
This looks like walking noise. Are you dithering in between images?
Well Written
Harry Karamitsos avatar
yes. every frame 10 pixels.
Harry Karamitsos avatar
Anyway to fix it?
D. Jung avatar
Is this the integrated or single sub image? If it's the integrated, can you show how it looks in a single sub?
Well Written Engaging
Harry Karamitsos avatar
Here is an integrated frame and a single sub of ~ the same field. 



andrea tasselli avatar
You are doing something very (too) agressive against noise. So do tell us what is the processing pipeline.
Dan Brown avatar
Were you dithering both axes? What program did you use to stack the images? Looks like the brightest pixel was used for the final result instead of the average.
Dan
Insightful Concise
Harry Karamitsos avatar
I stack with weighed batch processing script in pixinsight. I use flats and darks. Drizzle x2 is checked. I tried with and without linear defects correction with no difference...

Harry Karamitsos avatar
Dan Brown:
Were you dithering both axes? What program did you use to stack the images? Looks like the brightest pixel was used for the final result instead of the average.
Dan

I use NINA with direct guiding and a dither of 10 pixels.
D. Jung avatar
Can you disable drizzle for now and set the exposure tolerance to 1 to avoid integrating different exposure times?
Well Written Insightful Concise
andrea tasselli avatar
Ah well, WBPP is no-man's land to me. But definitely isn't dew.
Harry Karamitsos avatar
D. Jung:
Can you disable drizzle for now and set the exposure tolerance to 1 to avoid integrating different exposure times?

I'll do that now.
Oskari Nikkinen avatar
Have you checked that your dithers actually happen? This looks like a textbook example of walking noise due to insufficient dithering.

Blink your frames before registration and see if the data is actually dithered. Would bet some money on dithers not actually taking place here.
Well Written Helpful Insightful Concise
Brian Puhl avatar
That's definitely walking noise.   Your dithering isn't working properly.
Well Written
Harry Karamitsos avatar
Thank you. I will stop the dithering ad see what I get tomorrow.
D. Jung avatar
Harry Karamitsos:
Thank you. I will stop the dithering ad see what I get tomorrow.

https://youtu.be/txATxNaNeMQ?si=Uup8LhE3dm6h6lge

Blink your images before registration and check if they are actually dithered.
Michele Rainville avatar
Why are you using direct guider instead phd2?
Harry Karamitsos avatar
My set up is remote and the guider isnt working. My planewave has really good tracking but I figured I could ditther with the direct guider.
Michele Rainville avatar
I see I tried direct guider with my setup instead of phd and all it did was move my mount  and my guider would correct the error lol. I didn’t experience the same amount of noise but I’m sure there is some
Brian Puhl avatar
If the guider is correcting, you can try add stop guiding command, then your dither, then start guiding.    This may fix the error.
Stjepan Prugovečki avatar
What do you use as a guiding routine ( PHD2 ?) ? If so do use PHD2 to do dithering. I think (could be wrong of course) , tha thr Direct Guiding in NINA is not made and is not replacement for guiding (to replace PHD2) . It is more to be able to initiate dithering if you do not do active guiding (either short exposures or mount with encoders). I am using direct guiding to dither my mount that has encoders and I do not guide at all. Dithering there works perfectly and no walking noise  whatsoever.
Harry Karamitsos avatar
I'm not guiding. I started using direct guiding so i can try dithering…
Bob Lockwood avatar
Harry Karamitsos:
I'm not guiding. I started using direct guiding so i can try dithering...

Are you in the US ?  sounds like you need to make a trip to the remote site and get the guider up and running again. If not, maybe you can have someone at site take a look.
Better to fix the issue then try and bandage the problem.
Harry Karamitsos avatar
I am, remote site is in New Mexico at a place with bottle 1 skies. I live in New York… going in a week.
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