M51 LRGB

[jeffweiss9]

I haven't posted here in a while (few images this past winter) but conditions are now better and here is a recent 7.6 hr LRGB of M51:

http://www.astrophotogallery.org/showphoto.php?photo=9549&title=m51-lrgb-reprocessed&cat=500

Processed entirely in PI (except for making the jpg and printing locally), it took a couple of processings to (mostly) overcome some difficulties with hot pixels (sworn to always dither from now on) and color retention in certain PI steps, but feedback is appreciated.

Thanks,
-Jeff

[chris_todd]

It's hard to be critical of an image like this that is so much better than anything I can produce!  Very nice image!  I have to admit my initial impression was that the arms are very blue.  Perhaps you could try tweaking with the ColorSaturation tool to knock down the blues some and bring up the reds a bit?

[Josh Lake]

The link's not working for me at this point, but I'd love to see it.

For the hot pixels, have you given Cosmetic Correction a try? It's worked wonders for me (once I learned how to use it via Harry's video). Kill the buggers before you even get to Image Integration and you're a happy man.

[jeffweiss9]

Thanks, Chris, JLake-
   The link should be working again (although evidently not fully functional due to an 'upgrade'). The Kool blue is definitely off-standard. I did try manually adding red and knocking down the blue saturation but decided, at least for the moment, to stick with what came out from PI's ColorCalibration and the saturation curve I had applied, peaked in blue since I just liked it better (but probably wouldn't enter it in any contest).  I'm planning to collect Ha data which should strengthen the reds, as well as bring out the H2 regions.  Got some last night but it's probably not usable due to being shot basically from inside a giant thin cloud covering my hilltop field site (Montebello CA).  But I did see that H2 from this galaxy is coming from fairly limited regions, so we'll see if eventually the reds get pulled up.
  I did use the new CosmeticCorrection Module as standalone (actually several different times) but it gave me bad results with lots of residual hot pixels, so I went back to the CosmeticCorrection Script which did better but also resulted in lots of residual hot pixels I had to clone out manually (hundreds, in fact).  I don't really understand why so much trouble with this image, as I never had that much issue with residual hot pixels after CosmeticCorrection (Script) was applied.  I regret I did not dither and plan to do that going forward to make sure this doesn't happen again, but I would sure like to understand what happened in this image.  It was taken from a very dark site with long total exposure so the best I can come up with is that I was just more sensitive to artifacts coming from my ST2000XM camera.
  Your feedback is noted and appreciated.
Clear skies,
-Jeff

[Lex]

Jeff;

I do absolutely like your M51; really nice!!

So the used scope was an Triplet Apo?

Congrats!!

[Lex]

BTW;

do you think it could be possible to show us a non-cropped version? I tried to image M51 with a 90mm f/6 triplet also but the galaxy turned out as a flea 

[jeffweiss9]

Thanks very much, Lex-
  Yes, the APM 130/780 is a triplet APO at f/6.0 with the LZOS TMB lens set.
There wasn't too much cropping but the full frame is at

http://www.flickr.com/photos/9906726@N08/7179306270/in/photostream/lightbox/

Clear skies,
-Jeff

[Lex]

Okay,

Thanks for the info!

I had to crop about 4/6 of the surrounding background to see M51 closer, perhaps due to the pixelsize or the binning factor differencies...

[jeffweiss9]

This is an HaLRGB version with 3.6 hrs of Ha added for 11.1 hrs total but it is really only Ha-enhanced due to high sky background in the Ha data (need longer subs, I believe):

http://www.astrophotogallery.org/showphoto.php?photo=9572&cat=500&title=m51-halrgb

The galaxy still tends toward the cyan but looking at a number of PI processed image of this (and other galaxies), it appears to me that the cyan is predominantly from the PI ColorCalibration process that uses the myriad stars and star types in the galaxy to set the white rather than pretending deep space objects would have a color balance with white set by a G2V star like the sun.

-Jeff