Telescope Reviews: Convince me I need Photoshop

I posted this before in a different thread, but I'll put it here as well with some recent modifications.

My normal processing flow is something like this...

In Photoshop..

Use the Color sample tool to tag 4 points around the image in the darkest emptiest areas. Now you can watch your RGB values across your image when adjusting levels/curves.

3-4 Curves to bring the skybackground to levels around 80-100. These curves are almost always 1 point @ Output 190, Input 128 on the 'curve line'.

Levels to set black point so sky background is around 30-40.
(adjust left slider towards data on histogram)

Levels to adjust the middle slider to color balance the RGB values. (each color separate and watch your point values you set in step 1)

Star Reduction to about 75-80% (using http://astroanarchy.blogspot.com/search/label/PS-actions)

Curves, set a point at the sky background and stretch the higher end to a desired level. If you are worried about blowing out a galaxy core or other bright area then deselect the core with a high 'feather value' to help supress the 'blowout'.

If you end up having to stretch far enough that you can't get you background levels down to 30-40 without clipping data from your object then what I do is this.. Select a small area of background that contains little to no stars. Copy and paste as new image, then gaussian blur to create a smooth color. Select this color with the eyedropper, then go back to your original image and duplicate it. Now select all and delete the image(in the duplicate), then use the paint bucket to fill the entire image with the color you selected. Now go back to your original image and 'apply image' using your solid color image and 'subtract' mode. This will darken your sky background once again without destroying any nebulosity. This can also be an effective tool for removing a light pollution 'glow'. Now you can also run another set of curves if needed to being out even more faint stuff.

One thing I strive for is to get a smooth transition from the object to the background so nothing looks 'clipped'. I never use eyedroppers in the levels tool to set black/white/grey points as I find this almost always clips data. I'd much rather use the above method to eliminate as much background lightening as I wish after stretching.. The more subs in an image the easier this goal is to obtain I find. 30+ subs I find is very nice at creating a background that's easy to work with, at least with my 450D.

Possible Gradient Removal using GradientXterminator. (http://www.rc-astro.com/resources/GradientXTerminator/)

High Pass Filter using a Layer mask to bring out the dust lanes to a desired level. Careful not to halo the stars near and in dust lanes. (use eraser tool if necessary)

Possibly increase color saturation depending on the DSO imaged. This is done using the LAB mode method and which allows for a gaussian blur on the color data only to help with noise reduction.

I also sharpen the lumenance in LAB mode with a unsharp mask or smart sharpen.

Select Background and run a Deep Space Noise Reduction. (http://actions.home.att.net/Astronomy_Tools.html)

Run a light pass of Noise Ninja to remove any overall noise.

Then usually just a small unsharp mask over the entire image.

Of course, this isn't set in stone and sometimes these steps are mixed up a bit. Or perhaps there is more masking or selective curves based on bright or dark area's.

With the above image I increased just the blue channel with a curve in order to get a desired look as I thought the original color balance was too green. I also did one other thing that I don't normally do or like to do, and that was I changed the hue on the magenta color in order to get the yellowish glow from the center of the galaxy. I really don't like changing color hues but for some reason I ended up with a weird magenta tone throughout the center of this galaxy. I also selected the reddish area's through the galaxy with a slight feather value and increased the red coloration through the saturation adjustment tool. In order to help pop them out from the spiral arms.

I think that's about it... lol

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Celestron CPC 1100 XLT, Sky-Watcher Equinox 80ED
TV 31T5-Nagler, 8&13mm-Ethos
EarthWin Binoviewers w/ 24mm Panoptics
Elusive Photons.com