Abell 1656 - The coma cluster of galaxies - 9h with OSC

[ONIKKINEN]

Abell 1656 is a rich cluster of galaxies with a mean distance of 336 million light years from us here on Earth and contains as many as a thousand galaxies. In this image i can confidently say that at least a few hundred individual galaxies can be seen, some better than other of course. The cluster contains mostly photographically uninteresting elliptical galaxies which lack star formation and so have a uniform warm white colour to them due to the lack of young hot blue stars. There are some spiral galaxies and irregular galaxies too of course, but none have cleared the noise level yet to be well resolved with their features (perhaps with the exception of NGC4921). Everywhere i look in the image i see a faint background galaxy, its really mind boggling to be honest at just how many stars could be in this image and how many of those could have rocky planets and how many of those have someone pointing their version of a newtonian reflector towards us at this moment? I dont think its unreasonable to say that the number is not 0. I could daydream about stuff like this forever, which is why i wanted to shoot this target that, lets be honest, is not the most photographically interesting one.

And the (silly) annotated version:

Shot with my stuff which is the VX8, RisingCam IMX571 OSC camera and the AZ-EQ6.

Shot over 4 nights in total, of which the last one i unfortunately scrapped completely due to seeing, so 3 nights and 9h stacked for this shot. Was aiming for a much longer integration and i dont think its quite "there" yet but the season has ended, so this will have to do for now. I shot from a bortle 4 zone using only 60s exposures, just to prove to myself that the process of taking short subs and getting faint stuff out of them works, and i can say that it does since the subs themselves only had as few as 30 electrons of median background signal! Also, it was windy as hell so not much sense taking longer subs from that sense too.

Processing tools used: SiriL, GraXpert and photoshop.

After calibration i split the subs to their individual colour filter channels without debayering and vetted those with the plot drawing function in siril. I used simple measurements to make the calls, like: FWHM, roundness, background level etc to remove outliers. In the end i stacked somewhere around 500 red and 550 blue subs and more than 1000 green subs to recomposite back into a colour image, but now with improved SNR and a more reasonable sampling rate of 1.84'' per pixel compared to not bothering with splitting. The red channel ended up lacking since i had a bit of an oopsie with an uncovered rear of my scope and a red LED on the mount blasting light directly inside the tube for a while on my first night, but since i split the data i was left with working blue and green channels for that, so not a huge loss.

Comments and feedback welcome!

[Mr Spock]

Mind boggling indeed. There are so many galaxies in there! Lovely image of them though 👍

[Lee_P]

Oh wow, that's quite something.

[callisto]

Jaw dropping indeed 😲

[vlaiv]

Beautiful image!

[Ratlet]

Incredible.

[JeremyS]

Amazing 

[barbulo]

Wow! What a bunch of galaxies!

 

[ONIKKINEN]

5 hours ago, vlaiv said:

Beautiful image!

Thank you Vlaiv, i have learned much from your expertise!

Actually not just much, perhaps most of what i know today 😅. I think i would still be drizzling DSLR images with 7'' FWHM stars if i had not found this place and the experts in it...