M13 DSLR

[26Left]

For a big bright target, I find M13 quite difficult to image and process. It's difficult to bring out the outer stars without burning out the core and, at the same time, trying to keep some of the colour.

This was my first time using Nebulosity. I've given up on DSS. It just seems to blow out the colours.

This image is the result of 26 x 3 minute guided exposures through a Meade 5" on to a Nikon D90.

Cheers,

Tom.

[AndyUK]

Very nice Tom! Not only have you got some great resolution, contrast and nice star colour, but you've also managed to keep the noise down as well... Like it a lot!

[26Left]

Thank you

Not sure what the protocol is here for uploading images. The original is 2464px and I reduced it to 800px wide to make it more manageable.

My mission for the next few pics is to try and retain star colours. I have had a habit of clippling off the top end and burning out the brighter stars.

[hayju01]

nice one! I'll second the well done on keeping the noise down on that!

[26Left]

Thanks. As I said, it's more first shot with Nebulosity. For the last year, I have used DeepSkyStacker. It's always confused me that DSS creates grey images. Average or median stacking should end up with an image of about the same brightness, but less noise.

So, I stacked manually in PhotoShop and realised what you really gain with stacking. That is, you don't immediately get more detail, but you get less noise and the opportunity to pull out detail from the depths.

Nebulosity gave me a very similar result as manually stacking, but quicker. I don't know - maybe I have been using DSS wrong.

[AndyUK]

If you're happy with Nebulosity then that's great. However, I had issues getting colour data out of DSS until "Deneb" gave me some assistance and told me part of his workflow, which seemed (seems) to work very well for me also.

For DSLR images, aside from the subs (obviously!), I now use flats and bias frames to begin with, generally using Median Kappa Sigma clipping for all (as I usually have more than 20 subs). After alignment and stacking and the image draws, I now perform some additional processing in DSS:

1. Align and adjust RGB/K levels so that the 3 channels are aligned at the same point which is at the lowest part of maximum incline on the curve

2. Luminance - [starting settings] - Darkness 2nd slider 90.1, Midtone 1st slider 9, 2nd slider tweak to ensure that the maximum incline starts at lowest point on the curve

3. Saturation - Move to c. 21

I then save this as embedded (as a negative) and also applied, which is the one I then open in PS.

If the result appears to have hot pixels, then you can either try the same process but using the DSS cosmetic tab prior to stacking (check "remove hot pixels"), or you can replace the bias frames with darks...

It's a bit rough and ready and I'm sure others will have different variants (or maybe even disagree), but this seems to give a much better starting point for me when PS processing a DSLR image.

[26Left]

Thanks. I'll give it another shot using that workflow. I went as for as adjusting the RGB curves as you describe in point 1. Then, I exported to PS.

[AndyUK]

No worries - Please do let me know how you get on. I struggled with lack of colour in my DSLR shots for months before Nadeem told me how he did it...

[Coco]

wonderful star separation. I think with a few tweaks you have the makings of a fine M13..

How about a better crop up closer?

[26Left]

Getting closer shows up the imperfections. But here goes...

[AndyUK]

It still looks very good to me... (but please do try a reprocess in DSS and increase the saturation - Hoepfully you'll find some more star colour in there... )