Whirlpool Galaxy M51

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.

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

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.

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.

Great result @kijja 😉 Thanks for sharing !

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

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

Hi guys,

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

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.