About the Blog

This blog contains recent projects, activities, and musings about astrophotography and space, to view my main webpage with prints for sale, final images, and Annie's Astro Actions, please visit: www.eprisephoto.com


Thursday, November 19, 2009

Processing Comparison of M42

I very quickly learned a few months ago when I started astrophotography that processing made all the difference in shots. Yes, it takes some skill to set up a shot and different equipment can make quite a difference, but where the real photos are set apart from the rest are in the processing. I am by no means an expert. In fact, quite the opposite. As I said, I just started this a few months ago, but I am hoping to continue to improve and share some techniques I am learning along the way.

M42, the Orion Nebula, is a fairly bright object in the sky. In fact, even just looking at Orion's belt with the naked eye you can see the fuzziness caused by this nebula. There are alot of subtleties in the nebula, both with bright and dark nebulosity that are brought out with longer subexposures and processing. I am limited to an alt-az mount right now, so my exposures are 30 seconds at the most. So, I thought I would do a comparison of a few different types of processing of my latest data of M42.

The general data for this shot is as follows:
Taken with Meade DSI II Pro camera (monochrome) taking L,R,G,B channels
Orion EON 80ED scope piggybacked on my CPC 800 XLT
30 sec subexposures: 120xL, 40xR, 40xG, 40xB, total of 2 hours of data
I stacked the subs into channel files using Nebulosity

The three different types of processing I am going to describe and show the results from are:
1) Carboni's Astro Tools
-using ONLY the Photoshop Astrotools plugin (except for 1 rendition of levels to balance background and set the gamma level). This includes creating the RGB and processing

2) Photoshop processing of stacked, unprocessed LRGB channel files (ie stack the files first into an LRGB image THEN process it).
-I used Nebulosity to stack into an LRGB file and threw everything, including some of the AstroTools at it

3) Photoshop processing individual files first, then combining into LRGB, minimal additional processing
-stretched and processed L,R,G,B channel files, then combined using photoshop and added a few more steps to that outcome

Here are the steps for each type of processing I took, and its result.
1) Carboni's AstroTools
-Construct RGB image from Channel Files
-Enhance DSO & Reduce Stars
-Local Contrast Enhancement
-Fade Sharpen to Mostly Lighten
-LEVELS: balanced background color using color sampler, adjusted gamma (middle slider) just to right of histogram
-Enhance DSO & Reduce Stars
-Make Stars Smaller
-Local Contrast Enhancement
-Deep Sky Noise Reduction

2) Photoshop processing of stacked, unprocessed LRGB channel files
-Stack individual channel files in Nebulosity
-Duplicate Image
--Actions (AstroTools): Make Stars Smaller
--Curves (3 iterations)
--Levels - balance background, adjust gamma
--Curves (2 iterations)
--Levels - balance background, adjust gamma
--Actions (Astrotools): Local Contrast Enhancement
--Gradient XTerminator plugin (medium-medium)
-Original Image
--Image->Apply Image (apply copy): Overlay - 50%
--Image->Apply Image (apply copy): Add - 50%
--Image->Apply Image (apply copy): Lighten - 50%
-Increase Saturation 25%

3) Photoshop processing individual channel files and combine in PS
-Open all individual channel files (L,R,G,B)
For each channel:
--Levels - adjust gamma slider just to right of histogram
--Curves (2-3 iterations)
-Add RGB channel files to blank rgb image
-Paste L as new layer, blending: Luminosity
-Levels - balance background using color sampler
-Curves (2 iterations)
-Actions (AstroTools): Local Contrast Enhancement
-Layer Mask of unprocessed stack onto above process (Opacity - 53%)
-Actions (AstroTools): Make Stars Smaller

Unprocessed Nebulosity Stack (LRGB):

Side-by-side Comparison:

From these 3 types of processing (I know there are many more), while all 3 work and do show some nebulosity detail, in my opinion, processing individual channel files prior to stacking resulted in more detail in nebulosity and better color than processing the collective stack or just using Carboni's AstroTools.

1 comment:

  1. This is indeed very good work, shows great dedication. Sharing various post-processing techniques... I am impressed.


Monitor Calibration

Monitor Calibration
The grayscale above presents 24 shades of gray from pure white to solid black. If you cannot see all 24, your monitor needs calibration to view the astrophotos correctly: I recommend the site linked in the image