M81 - DSLR

[Tzetze]

Hi folks. After having a bad run of attempts at imaging galaxies, I realised that my ASI120 camera just wasn't up to the job of guiding through an OAG. I was getting too much random noise along with low SNR on even the brightest of stars. This was causing very erratic guiding with the star 'lock' jumping from star to noise. Not to mention the fact that it was very difficult to locate a guide star and keep the intended target in frame.

So, I decided to go for the Lodestar x2 guidecam. Wow, what a difference! Fantastic SNR, even through the OAG, and always a guidestar in frame when I get onto the target. Highly recommended as a guidecam.

Got onto M81 last week and got some super smooth guiding with 0.46 arcsec average error.  8)

After many poor attempts at processing, I'm finally happy with the results (although there is still an LP gradient in the image). I had to create new bias and dark libraries, the old ones were up to 6 years old and the nosie signature on the old DSLR has surely changed in that time.

Here's M81 with 5hr 10m integration, made up of 31x 600s subs.
(Click on the image to see more technical data)

Any pointers towards improvement would be more than welcome.  =]

[MarsG76]

Excellent image....

No pointers to give.. I should take a few from you.

 

[tooth_dr]

No pointers, damn fine image 

[Tzetze]

Thanks MarsG76 and tooth_dr. I'll have to criticise it myself then.

I combined a star/galaxy core mask with an inverted luminance mask to make a mask that would protect the background and cores while pulling luminance and saturation curves. My machine crashed before I'd finished the saturation pulling and rather than go through the process of making a new mask, I cheated and made one final saturation boost without one. Now, I can see a blue tinge through the entire background (as well as the LP gradient). I'll have to work it out from an earlier save.

[alan potts]

Lovely image there with nice detail and colour, I have just bought the Lodestar, superstar for a guide camera but I was not able to find focus first time out with it and since weather had been poor, now we have 18 inch of snow and it's still at it.

Alan

[Demonperformer]

That is a very nice M81. 5 hours well-spent, I would say.

Plus, of course, all the extra hours at the computer afterwards ...

[Tzetze]

Thankyou both, Alan and Demonperformer.   =]

[Jannis]

That's a really nice image you have there!

You could try these 4 steps in Photoshop that i think improved it a bit. It's usually noisier in the red channel, and in the full res image you can see red spots here and there.
1) after duplicating the image as a new layer, reduce the noise. I tried these settings:

2) Filter -> Blur -> Gaussian Blur. I tried 3 pixel radius in this case. Just to smooth out the colors a bit, but not enough to loose too much of the smaller color details.
3) Image -> Adjustments -> Hue/Saturation. Increase saturation with +10 or so, just to compensate a bit for the faded colors due to the previous steps.
4) Set layer as "Color", and you will have the original sharpness, but with a more smooth color.

Note i did not take the star colors and background into account here and it's often good to protect them a bit, as well as the previous steps can also be tweaked a bit, but give it a quick 30 sec reprocess with the galaxy color in mind and see what it does.

[SteveBz]

5 hours? How did you get that amount of clear sky? The last time we had a clear sky was at full moon!

Anyhow, great image. M81 was horrible.

Steve.