A quick M51 luminance process

[JamesF]

I thought I'd give last night's data from the ED80 a quick look over, so I stacked the luminance, stretched it and gave it a teeny sharpen.  Possibly I've stretched it a little too far, but other than that I don't think I'm unhappy...  It's two hours ten minutes as five minute subs, ED80 and 314L+.  I've reduced the size by 50% just for speed for the time being.

Pleased to see the tiny edge-on galaxy just to the left of the smaller of the pair, though it is very faint.  I'm fairly happy with the framing, too.  I wouldn't mind losing the bright star at the bottom of the frame, but I want to keep the edge-on galaxy at the top right.

Probably worth a revisit with ten minute subs I think, though given the amount of clear sky we've had in the last ten days it'll be Christmas before we get another clear night   Perhaps a quick peek to see if there's any Ha worth having, too.

Now I just need to work out how to align my binned colour subs with it.  I don't think DSS can handle that.

James

[geoflewis]

Looking good James, hope you can work out how to combine the binned colour so that we can see the finished image. I don't use DSS and anyway to avoid that problem I always shoot all my subs for any target at the same binning, bin 2x2 with my C14, or bin 1x1 with my 4" APO.

A tweak with a high pass filter might sharpen the spiral arms structure a tad, but you need to be careful to mask the stars.

[JamesF]

53 minutes ago, geoflewis said:

Looking good James, hope you can work out how to combine the binned colour so that we can see the finished image. I don't use DSS and anyway to avoid that problem I always shoot all my subs for any target at the same binning, bin 2x2 with my C14, or bin 1x1 with my 4" APO.

A tweak with a high pass filter might sharpen the spiral arms structure a tad, but you need to be careful to mask the stars.

Binning the colour data was mainly an attempt to reduce the capture time required because of the lack of clear sky.  I have so much "unfinished" data that I've captured over the last few months because there's not been time to get everything.

I'll have to see what I can do about masking stars.  It something I've been meaning to get my head around for some time.

James

[JamesF]

Hmmm.  Not really sure I've quite done this justice yet.  It looks better on my laptop screen than it does on my desktop, too -- the colours are more vibrant.

It was a bit of an experiment to start with mind.  I don't have any software that will align and stack binned images against unbinned ones, so I fudged it in DSS.  I registered and stacked the luminance data (with darks) in DSS against a reference frame and then stacked the RGB data with their own darks.  After that I resized the RGB frames to the same as the luminance and registered and restacked just those three frames against the reference luminance frame in the hope that I would end up with LRGB frames all with the same orientation.  I can't imagine I'm the first one to try it.

Processing was nothing incredibly clever in PS -- mostly levels, curves and sharpening.  I feel that I've lost some of the luminosity around the smaller galaxy which I'm not happy about so I might have to look at that again.  On my laptop there's also a bit more of a blue bias I think, giving M51 a slightly more violet colour, though it looked a lot worse until I remembered I have the night-time colour adjustment running on my desktop monitor   Looks as though there's a bit of a blue/red gradient in the background, too.  Then again, I was capturing this data with a fairly bright Moon in the sky.  I think star colour and alignment may have suffered a little from the messing about with stacking.  That bright star at the bottom is looking a touch green on one side to me, for a start.  Still, I'm very much at the beginning of my DSO processing journey so I'm not going to get myself too distressed about it, though I may have another pop at it when I've processed some of my other data.

My "occupational" glasses aren't quite ideal for processing either.  They give stars odd shapes unless they're centred my in view.  I'm going to have to find a better way to do this.

For the record, 2 hours 10 minutes luminance as five min subs, 54 minutes each of RGB as three min subs, so a smidge under five hours in total.  80ED and 314L+.

James

[MarkAR]

Looking good, maybe just a little on the dark side.

Peter Zelinka just released a vid on Youtube about LRGB. 

IIRC he stacked the individual channels separately using the same reference image (not included in the stack), them mashed them all together in PS.

[geoflewis]

Looks good, but as Mark says maybe a bit dark, something that a tweak with curves can probably fix....