Ngc55

[DiscoDuck]

An attempt at NGC 55. Trying to get some more detail with my new ASI1600MM-C compared to my old QHY8, so selected the best 184 out of 241 60 second Luminance subs - those with less than 3" FWHM average. A bit of an arbitrary bound on the sharpness I guess -- comments welcome??

Couldn't get a decent non-windy night to get some reasonable RGB data so used some old QHY8 data for the colour.

Minimal overlap of the two images means I was forced to crop just the galaxy!

Full res on Astrobin (http://www.astrobin.com/full/316648).

Still struggling with some noise in the fainter areas (edges) of the galaxy, with only 3 hours of L in the 'burbs so found it hard to process. Tips appreciated, e.g. blending that galaxy edge in more smoothly with the background somehow??

Thanks for looking.

Paul

[glend]

Can you post just the 1600 luminance? And what ADU value were you getting in the dark section of your subs? Thus will inform sub sky glow. What scooe was used?

[DJT]

Nice one Paul. Just picked up one of these ASIs to play around with the RC so good to see what you have been able to do with that combination.

Did you do any star morphology with this?

[multiweb]

That's pretty good. Great details and colors. :thumbsup:

[Placidus]

Very sharp and crisp. Some nice background galaxies too.

[strongmanmike]

Not bad Paul, at only 7 Million light years and over 1/2 deg in apparent size (bigger than NGC 253) this is a great galaxy for getting some good detail out of and you have managed to do just that here.

The background is a bit blotchy but I like the delineation of the HII regions and all the dusty detail, overall a good galaxy image mate :thumbsup:

Mike

[DiscoDuck]

Glen, the luminance is here (http://astrob.in/317240/0/). It's nowhere near as heavily processed as the final colour image - it is still quite rough.

For the subs, the background (gain 139) was at the lowest (near the meridian) about 570 ADU over bias, so quite well shot noise limited (60 sec exposures). Noise on each frame was about 7electrons - so most of that from light pollution, with a smidge dark noise. At the faint ends of the galaxy, the signal in 60 seconds was about 2-3 electrons. Once stacked, noise was down to about 0.5 electrons, but those faint areas are then only 4-6x above the noise at best.

The scope was an RC8.



Thanks David. No morphology. Just a tad deconvolution.



Thanks Marc.



Thanks Mike and Trish.



Thanks Mike. If there's anything to fix that faint blotchiness, I'm all ears. I suspect though it's simply from the bit of noise reduction applied (and that wasn't much) and I just need longer total exposure time than the 3 hours used there??

[alpal]

Nice picture Paul.
Photoshop can clean up that noise by using a blurred layer mask -
reducing the colour selectively in each channel, and adding noise.

see here but use a mask so you don't add noise to the galaxy:
http://bf-astro.com/backgndrepair.htm

Note: you can do better than the link by selectively doing it to each color channel.

cheers
Allan

[DiscoDuck]

Thanks Allan. Will try that. Much appreciated.

[RickS]

Looks good, Paul! What software are you using for NR? In PI you can build a mask for the background and just remove a few layers with one of the multiscale tools like MMT. That will clean up a messy background quite well.

Cheers,
Rick.

[DiscoDuck]

Thanks Rick. Re NR I used PI's MLT with a mask, plus a bit of TGV I think. It's just that transition from the galaxy to the background I'm not fully happy with.

[RickS]

That's tricky, Paul. Sometimes Convolution to soften a mask will help with the transition zone.

[DiscoDuck]

OK. Thanks.