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20th March 2020 - APP 1.078 has been released !

2019 November: Complete LRGB Tutorial of NGC292, The Small Magellanic Cloud by Christian Sasse, Astronomer in Charge of iTelescope.net

2019 September: Astro Pixel Processor and iTelescope.net celebrate a new Partnership!

M31  

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(@vjagannathan)
Molecular Cloud Customer
Joined: 2 months ago
Posts: 5
February 18, 2020 06:19  

Here are two pics of M31 processed with APP. They were taken with WO's 51mm f/4.9 Petzval space cat refractor mounted on an Ioptron sky guider and using a modified Canon T7i further containing an Astronomik filter to counter light pollution issues when shooting from a city. 

One of them is at 31 x 90sec at ISO 1600. Only light frames. No darks and no flats.

The other one is at 28 x 180sec at ISO 1600 i.e. doubling the exposure. Again, only light frames.

I see a bit of an improvement in the latter. 

I think that the TOOLS tab #9 in APP is a real gem although it does take a lot of experimentation to get it do what I want it to do. If I can get a grip on it I think my images will also improve.
 
I have a concern in that I did not apply cold pixel and hot pixel type of corrections to avoid "losing" some stars but is so doing my images are a little dirty. I also did not take any dark frames to further reduce noise. I also did not shoot different parts of M31 at different exposure parameters and combine them into an overall mosaic. Now, I am wondering how much these would have affected the final image. My question is how far can one continue this experiment to get better results?
 
Any critiques, constructive advice/suggestions would be appreciated.
 
Andromeda 02142020 v2 St avg 5054.0s SC 1 3.0 none x 1.0 LZ3 NS full qua add sc BWMV nor AAD RE noMBB lpc cbg cbg csc mod St
Andromeda 01292020 v4 St avg 2795.0s NR x 1.0 LZ3 NS full qua add sc BWMV nor AAD RE noMBB mod St

 

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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1451
February 18, 2020 12:36  

Great first results and good that you're open to suggestions! Having proper bias and darks will definitely improve the result. A nice long dark and (when you have cold pixels at least) a good flat will make it possible to create a BPM (Bad Pixel Map) which you can use for quite a long time to correct for all the hot pixels and such. Don't worry about the stars, this shouldn't be a real issue. Dithering will further help you in reducing noise (for instance it might lower the vertical stripes in your background).

Flats, always a difficult topic and tricky to make proper ones, definitely is a good thing to learn. It will enhance the overall quality as well by a lot. You have some dust on your frames (the darker spots) and these can then be removed and the overall background can be corrected much nicer. When you have all this in place, you can go and experiment with longer exposures or at the very least, more frames. I would keep the best frames of these attempts and add more later, aim for 100 or so in total and see the improvement.


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(@vjagannathan)
Molecular Cloud Customer
Joined: 2 months ago
Posts: 5
February 18, 2020 15:16  

Thank you @vincent-mod. I really appreciate your careful response. Thank you for clearing up my fears about "losing" some stars by applying corrections without understanding how they work. I especially like the idea of saving good frames and to bank them for future processing. This means that no session is ever completely wasted. For the flats, I thought that because of the Petzval design that I didn't need to fight that battle this early. Again, my appreciation to you for taking the time to help me improve.


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1451
February 18, 2020 15:21  

No problem at all Vasu, always nice to help if someone wants to learn more! If you have any further questions or run into trouble, don't hesitate to ask more.


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