Whirlpool Galaxy M5...
 
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The problem with the data upload limit for attachments has been fixed. I have restored it to 30MegaBytes. A recent forum software upgrade was responsible for the changed limit. Please accept my apologies for missing this when upgrading the forum sofware, Mabula.

Whirlpool Galaxy M51  

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(@kijja)
Red Giant Customer
Joined: 2 years ago
Posts: 67
05/02/2019 5:32 am  

Hi all,

The image of M51 was taken during 3 nights with QHY10 on William-Optics GT71. The total integration time is 14400 seconds. Image processing was performed in the default setting of APP 1069. Adobe Photoshop cc was used for post-processing (noise reduction, curve and clipping). Hoping you will enjoy this as I do. Comments are welcome.

M51 14400


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(@oopfan)
Main Sequence Star Customer
Joined: 7 months ago
Posts: 35
06/02/2019 10:32 pm  

Hi,

Great image! You were up late acquiring that one this time of year.

I looked up the specs on your camera: 45,000 electrons full well depth -- very nice.

May I ask what exposure you used? I have the same telescope but a different camera.

Thanks.


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(@kijja)
Red Giant Customer
Joined: 2 years ago
Posts: 67
07/02/2019 12:20 pm  

Thank you @oopfan. My exposure for this image is 600 seconds at gain of 0.5 for each sub. I used SGP pro for acquiring these subs while I was sleeping 😉. It still need some more nights for details and clean background, or re-do with a mono ccd in LRGB (if I could afford one 😊 .

Clear skies,

Kijja


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(@oopfan)
Main Sequence Star Customer
Joined: 7 months ago
Posts: 35
07/02/2019 1:01 pm  

Hi Kijja,

Instead of a mono CCD you might want to purchase a quality 2x focal extender. I ran the specs of your telescope and camera through a "CCD Suitability Calculator". The result is that you are under-sampling. This would explain why your image contains green stars.

Your telescope produces a diffraction disc that does not cover the entire Bayer matrix, so sometimes the disc falls almost entirely on the green filter. A 2x focal extender will solve it at the expense of reducing your field-of-view. You could also experiment with defocusing slightly.

 


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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 2111
11/02/2019 5:46 pm  
Posted by: Kijja

Hi all,

The image of M51 was taken during 3 nights with QHY10 on William-Optics GT71. The total integration time is 14400 seconds. Image processing was performed in the default setting of APP 1069. Adobe Photoshop cc was used for post-processing (noise reduction, curve and clipping). Hoping you will enjoy this as I do. Comments are welcome.

M51 14400

Great result @kijja 😉 Thanks for sharing !

 

Main developer of Astro Pixel Processor and owner of Aries Productions


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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 2111
11/02/2019 5:55 pm  
Posted by: oopfan

Hi Kijja,

Instead of a mono CCD you might want to purchase a quality 2x focal extender. I ran the specs of your telescope and camera through a "CCD Suitability Calculator". The result is that you are under-sampling. This would explain why your image contains green stars.

Your telescope produces a diffraction disc that does not cover the entire Bayer matrix, so sometimes the disc falls almost entirely on the green filter. A 2x focal extender will solve it at the expense of reducing your field-of-view. You could also experiment with defocusing slightly.

 

Hi @oopfan and @kijja,

Yes, undersampling could be an issue here.

But I think using a 2.0 focal reducer is not a solution , because the F-Ratio will be twice as big, so ligth collection will be 4 times slower.

Probably best is to combine the GT71 with a camera with smaller pixels.

@kijja, did you debayer the data with AAD or did you use either drizzle or Bayer Drizzle integration here? Perhaps another integration method can reduce the artefacts on the stars 😉

Finally, another problem could be that the GT71 slighly has some Chromatic Aberration. If so, this can be solved with the Align Channels option in 2)

Kind regards,

Mabula

Main developer of Astro Pixel Processor and owner of Aries Productions


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(@kijja)
Red Giant Customer
Joined: 2 years ago
Posts: 67
12/02/2019 4:08 am  

Hi @oopfan and @Mabula,

Thank you for good advices on my image. I use AAD for this image but not bayer drizzle. It would be fun to redo this image again.  😘 

Cheers,

Kijja


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(@kijja)
Red Giant Customer
Joined: 2 years ago
Posts: 67
12/02/2019 5:19 am  

Hi guys,

This is my quick re-do of the image with bayer drizzle integration. 

 

St avg 24600.0s SC 1 3.0 none  x 1.0 3.0 bdr hat full qua add sc BWMV nor NI RL noMBB mod St Edit Edit

This post was modified 6 months ago by Kijja

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(@oopfan)
Main Sequence Star Customer
Joined: 7 months ago
Posts: 35
13/02/2019 3:21 pm  

Very nice @kijja

I am glad it worked! My first reaction is to solve problems at the telescope instead of applying image processing techniques. It's a lot of "voodoo" -- just kidding but it shows I need to learn more.

 


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