Grus Quartet

[andyc (Andy)]

My DSLR scene of the Grus quartet, 3hr 10min of frames. I'm struggling a little with background noise that's probably mainly because it's a DSLR, but there's a decent few background galaxies, including cluster AS1111 and a few more. 200mm f/5 Newtonian, more details at the links. It's the first picture where I've tried a little deconvolution too, but I couldn't be very bold with it, lots to learn! Comments on improving smoothing or background colour/noise level with DSLR images (or anything else) are welcome, the main background noise reduction is a masked MLT.

A larger view of the wider scene here
A full resolution view of the trio

[RickS (Rick)]

That's very nice, Andy! Good detail in the galaxies and all the faint stuff is visible.

You could have tamed the background by stretching a bit less but where's the fun in that I was guilty of pushing a little hard in my Astrofest image of the same region.

There's a slight gradient that DBE would take care of and you could clean up the background if you wish (perhaps a RangeSelection mask to protect all but the background and another MLT noise reduction or perhaps just delete the first couple of layers in MLT or MMT.)

I also identified Abel 1111 from a couple of annotated images but someone pointed out that this cluster was in the wrong place. After digging a little I'm pretty sure it is actually ACO 3998.

Cheers,
Rick.

[strongmanmike (Michael)]

Good result Andy, the framing that shows all four is beaut

Mike

[Atmos (Colin)]

T'is really nice Andy, you have picked up quite a lot of background galaxies which is excellent. I also don't tend to darken my background a hell of a lot, I sometimes find a good way is to play around with the lower part of the curves and bringing that down. I'll put half a dozen points along the curve line to keep it straight and then play solely with the lower end. As all you're trying to do is darken the background it doesn't damage the rest of the data a great deal.

[p1taylor]

That is really good Andy.

peter

[Retrograde (Pete)]

Hi Andy,

that looks really great - especially for a DLSR image.

Regarding the background noise I was wondering if you are already using dithering? (apologies if this is a stupid question)

[andyc (Andy)]

Thanks everyone for the nice comments!

Rick, great suggestions on the noise and processing. I always want to push hard on the stretching to get at the faint stuff, and invariably fall foul of the noise limitations of the DSLR. Looks like a CCD is in my future I used DBE, but you're right about the residual gradient. I should pay better attention to the results and residuals at that point!

Interesting about Abell 1111/ACO3998 - I'll look into that a bit more when I get back to my computer. Not easy to identify these clusters!

Colin, funny you should mention that method, it was exactly what I did between v3 and v4 of this image, the current version is plenty dark on phone and tablet screens, but still not all that dark on my laptop. It's hard with the noise to darken it enough without losing the fainter parts of galaxies.

Pete, it's a good question, answer is: not consciously, but this image had frames from three nights, sort of pseudo-dithering . But may not be enough to get around the coloured pattern noise you can get with the dslr.