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NGC 6960 Veil Nebula.

MikeWilson

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MikeWilson

MikeWilson

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Hi all,

Here's my image of the Veil Nebula. It's beset with a terrible gradient, in my opinion caused by the moon (far off frame and in the direction of gradient).

post-18683-133877495884_thumb.jpg

I took flats, darks, bias and stacked 5 x 10 minute subs and 8 x 5 minute subs (took 10, discarded 2).

I am processing using Photoshop CS5 and Noels Actions. I have tried following this guidance for gradient removal but I find that this clips the dark colours and doesn't give me a neat uniform gradient removal at all :*(

Gradient Subtraction

Any ideas on where I should look or what I should do next to improve this image?

Many thanks for your time!

Mike

Stacked data:

http://dl.dropbox.com/u/3717210/NGC%206960%20-%20Western%20Veil%20Nebula%20%2824-10-2010%29%208x5min%2B5x10min%20-%20Copy.TIF

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dlp

dlp

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Mike - I've been a photoshop user since version 2.5 (albeit using terrestrial photos), and I couldn't get anything remotely as good as your efforts from your tif file. I did have moderate success with the gradient, and I'm sure it would work with more fiddling - sample colour on left to foreground col, colour on R to bg col, new layer, draw standard gradient from left to middle, then set layer to screen mode, merge layers and adust levels.

Had a look for Noels actions with no success!

David

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MikeWilson

MikeWilson

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Thanks David. I'm guessing this means that even with your expertise there's a severe issue with the gradients that is going to be quite difficult to fix. I'm guessing that since the gradient is uniform and straight that it can be resolved but perhaps this is data to return to at a later date as I've spent ages on it and just can't get better than the sample I've uploaded here.

Thanks again :)

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dlp

dlp

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Oops - No I didn't mean that at all! Rather, with my photographic skills at photoshop I couldn't get your tif download to be anywhere near as good as what you have done! A compliment to your skills :). I've little or no experience with astro image processing yet. However, using the simple method outlined in my previous post I think you could remedy the gradient quite easily.

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MikeWilson

MikeWilson

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I see :)

Well, I wouldn't say my skills are anything more than a triumph of tutorial following. I did a series of steps similar to those you describe, except I sampled two colours at each extreme and made a trackage across the entire image. I then set the trackage layer to 'subtract' and opacity to 50% or so.

It took a dozen or so attempts to not get such a harsh overcorrection, however I can't see what I'm doing wrong as what needs to be done shoul be (to my mind) a straightforward and rather common task.

More Googling required, I think. If Keiran is still around, I'd be interested to see if he can conquer the gradient.my next step is to try PixInsight LE and try to extract the background using the background sampling tool therein.

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Tim

Tim

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Your PS skillz are coming on a treat Mike :)

Really, faint DSO's like this are best left for moonless nights, you just end up getting frustrated and wasting time on a target you cant make the best of.

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MikeWilson

MikeWilson

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Your PS skillz are coming on a treat Mike :)

Really, faint DSO's like this are best left for moonless nights, you just end up getting frustrated and wasting time on a target you cant make the best of.

Thanks TJ, but I do feel like I could use some lessons.

As for the choice of target - I wanted a nebula that wasn't totally washed out by the moon that I could get from my back garden. The Veil just came to mind. I was getting a bit carried away with guiding :mad:

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