M51 LRGB

[discardedastro]

Well, I figured I'd stick with a target for the two flawless nights of clear skies I got Thursday and Friday, and picked on M51.

Setup: Skywatcher 200PDS on EQ6-R, Baader LRGB in EFW Mini, ASI183MM-PRO at -10c, HitecAstro DC focus, guided with ASI120MC through a Primaluce Lab 60mm guidescope.

Capture: Post ditching the crap frames, 51xL, 25xR, 27xG, 27xB, all 120s exposures.

Processing: Stacked and processed entirely in PixInsight. General workflow was cal, hot pixel correction, registration, linear fit stacking, order a 32G RAM upgrade for next time, deconvolution on L, DBE on all, channel combination and photometric colour correction for RGB, multiscale linear transform noise reduction, histograms, LRGBCombination, final masked MLT and global TGVDenoise, a gentle ABE mixed in with PixelMath, local histogram equalization, a bit of gentle masked saturation tweaking, unsharpmask and curves.

Quite happy with the result overall, though there's still some calibration issues - I have no way to make flats and my darks are out of date and not at 120s so PI's optimisation didn't quite null out all the amp glow from the 183. Deconv is still slightly unsatisfying, even with careful masking.

[andy fearn]

WOW. Fantastic image. Does it take longer to process than to collect data ?  I can't get my head around this stacking business.

[Craney]

Great image.   On the strength of this, I'm getting my 200pds out again,  my C6 SCT is just not getting the light.

In answer to  @andy fearn.           This is a world class image from relatively modest equipment, all of which seem to be singing in perfect harmony. 

If everything goes right then the answer is 'no',  processing should be a few hours..'ish....., but you do have to know what you are doing and how to spot when you are over-cooking the image etc....

Obviously,     @discardedastro   holds the answer to that one.

 It's when the data is of variable quality, or the need to 'stretch' or process using the dark arts of astro-processing is when you fall into a black hole of time ....    I'm not a user of Pixinsight so I don't know how difficult those work-flow steps are.  They sound like they are from the Haynes manual of the Tardis...!!     I suppose the hard yards are done over the images preceding this one.

 

[Allinthehead]

This looks great despite the lack of proper calibration. Very natural looking too.

[discardedastro]

1 hour ago, andy fearn said:

WOW. Fantastic image. Does it take longer to process than to collect data ?  I can't get my head around this stacking business.

Thank you! So capture on this was two full evenings from about 6pm to 1am in terms of my time, about 8-9pm to midnight in terms of imaging. Got about 2 hours of luminance, and an hour for each RGB channel. I also captured an hour and a bit of Ha but haven't really worked out how to fold that in just yet, and didn't feel this needed it in the end.

Processing this took a bit longer than it should have, because my machine was running out of memory fairly often which PI dislikes so I had to throttle back the parallel processing side of things; my PC is actually now old enough that DDR3 1600MHz sticks are now cheap, so I've bought myself an upgrade to 32G to fix that for next time. I spent most of a day working on the image actively, in the end. I like to have control over each stage so I don't make use of the scripts like BatchPreProcessing in PI, and I worked through the whole workflow fairly (though not entirely) carefully, repeating a few steps over to adjust settings and so on. Takes a bit more time, but I can understand what it is I'm actually doing to the light a bit better - I don't want to end up creating something wholly artificial. So probably about twice as long to process as capture, but that's with perfect nights when I more or less hit "go" in Ekos and walked away...

I've attached a single luminance frame, quickly stretched, and the final luminance stack, cropped and again stretched for a quick demo. Need to sort the focuser out; my guiding was <~0.7" RMS all night so that's I think now mostly limited by the mount. Also need to get some proper collimation tools - all I have right now is a laser collimator. Flat generator wouldn't hurt either!

Thanks all for the very generous and kind comments.

[andy fearn]

Thank's for reply. I have managed to image M51 and having seen you'r single luminance i am actually very pleased with my result.

thanks again and clear skies.

[DougM43]

That’s a gorgeous image,,

I’m not an expert by any means and certainly no pixel peeper but that is as good as any M51 I’ve ever seen.

 

[mikemabel]

Again wow brilliant image , inspiring 

Looks like i will be pointing my ASI 183mm Pro at this one again in the hope of getting some RGB subs this time

[Trevor N]

Excellent. Great image

[peter shah]

beautiful image