Figure 14.13. The Orion Nebula (M42) in exquisite detail - a combination of 29 5-minute, five 1-minute, and five 10-second exposures at ISO 800 using a Canon XT (350D) and an Orion ED80 8-cm telescope with a focal reducer giving f /4.7. Wire crosshairs in front of the telescope produced diffraction. Processing included layer masking, Richardson-Lucy deconvolution, and noise removal with Neat Image. (Hap Griffin.)
This or almost any other image alteration can be "faded" by choosing Edit, Fade. What this does is mix the altered image with the previous, unaltered version of the same image, thus reducing the effect.
A large number of astronomically useful Photoshop operations, including quite complex ones, have been scripted as macros in Noel Carboni's Astronomy Tools Action Set (http://actions.home.att.net). These include unobvious procedures such as "make stars smaller" and "add diffraction spikes." They come highly recommended.
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