Sculptor galaxy, NGC 253, two nights ago from Taupo New Zealand. This is my first successful autoguided image, and the first astronomy image I have posted online in any public forum. I started my astronomy hobby about 6 months ago. Comments welcomed.
Taken through my Celestron C8-SGT XLT (C8 XLT OTA on CG-5GT goto eq mount), with f6.3 reducer, Canon 60D DSLR (unmodified) at ISO 1600, guided by Orion 50mm mini guidescope and SSAG, using PHD guiding software on a netbook.
10 x 3 minute subs,
5 darks, 5 flats (two layers of white tee shirt cloth stretched over aperture and led flashlight shone on it), and biases.
Canon Raw images stacked etc in Deep Sky Stacker and resulting tif image then processed in Photoshop Elements 9.
I also have a question. If I use DSS to wind up the saturation after stacking, the galaxy gets a strong green tone (but stars don't), whereas if I use Photoshop Elements to turn up the saturation I get a much more "balanced" colour in the galaxy. Any ideas why DSS saturation is giving the galaxy a green cast? I had exactly the same thing happen with an unguided image of the Sombrero galaxy taken some months ago.
I think I have finally figured out how to use the stretching in the output pic once its stacked in DSS.
What I do is adjust the black point slider on each RGB channel and bring it to the right until the channel widens and then "clips" where a SPIKE appears on the left of that channel. THEN, I slide it left one notch to remove the clip spike. This leaves the channel WIDE and stretched out. Repeat for the other two channels, trying to make EACH channel the same shape. Then I adjust the middle slider (grey point) so they three channels line up with each other.
Moving to the luminance page, I adjust the midtone sliders so the curve matches my attached pic and is placed over the three channels as shown.
Then I adjust the saturation to say 15-20% depending on taste.
Hit apply and whammo, a fairly nicely stretched image ready to slot into nebulosity or photoshop ready to be touched up.
Give this a go and see if it helps. It has seemed to work on my Atik photos as well as my DSLR shots (like the one attached), so I might be on to something.....
Thanks for those DSS stretching hints screwdriver. I'll try your approach next time and see if that helps get rid of the green cast when I up the saturation.
Thanks for your comment scagman. I was pretty happy with what was only my second ever attempt at autoguiding. I might try a slightly more challenging galaxy next time, perhaps NGC 1365 in Fornax.
Great shot Chris,
Good detail with lots of data. Guiding looks good, nice round stars. Focus could be a little sharper and play around with the colours a little more, looks a little blue to me.
That's a like from me.
I have a bahtinov mask for my C8 and must remember to use it for final focusing to get it spot on. I used the live view zoom mode of my dslr to do final focusing on this occasion but the bahtinov mask would I imagine be more accurate, assuming the spikes will be bright enough to see through the camera.
I went through various colour balancing attempts that were too green by far, too red, and then that one which I agree is a little too blue, but by then I'd tried so many combos of colour balancing in both DSS and Photoshop Elements that I eventually decided to stop at that stage.
