Craig Stocks
Well-known member
There are a number of approaches for astrophotographers.
For deep sky images from a telescope most use either Deep Sky Stacker or PixInsight. Both can process RAW files along with dark, flat and bias frames. They can also automatically align the frames as there is frequently some drift over time, even with a good tracking mount.
For widefield astro-landscape photos Starry Landscape Stacker (Mac only) or Sequitor (Windows only) are common. Again they can read RAW files, align based on star patterns and handle additional files to help manage noise and vignetting. They can also separate the sky portion from the foreground and process it separately (the stars move and need to be aligned, the foreground doesn’t move).
The various dedicated astro-stacking tools offer the advantage of stacking RAW files rather than demosiaced photos. They generally offer quite a few processing and averaging options that I’m not even smart enough to list, much less describe.
And of course you can use Photoshop but it only works on files after they’re processed from RAW. The old school way is by adjusting layer opacity once the frames are loaded into the layer stack. The bottom layer is at 100%, layer 2 is at 50%, three at 33%, 4 at 25% and so on. The result is the average of all layers. The modern approach is lo load the layers into a smart object and then choose a smart object stacking mode of Mean or Median. Mathematically the Mean stack mode is identical to adjusting layer opacity.
For noise reduction I’ve found comparable results frame averaging in camera versus processing in C1 and then stacking “finished” frames in PS. Stacking in PS is more hassle but does offer some flexibility advantages. If you’re using averaging in lieu of ND filters then doing it in camera can provide the advantage of continuous capture whereas individual frames will always have a time gap.
For star trails I simply load the frames into the layer stack and change all of their blending modes to Lighten, no smart object needed.
For deep sky images from a telescope most use either Deep Sky Stacker or PixInsight. Both can process RAW files along with dark, flat and bias frames. They can also automatically align the frames as there is frequently some drift over time, even with a good tracking mount.
For widefield astro-landscape photos Starry Landscape Stacker (Mac only) or Sequitor (Windows only) are common. Again they can read RAW files, align based on star patterns and handle additional files to help manage noise and vignetting. They can also separate the sky portion from the foreground and process it separately (the stars move and need to be aligned, the foreground doesn’t move).
The various dedicated astro-stacking tools offer the advantage of stacking RAW files rather than demosiaced photos. They generally offer quite a few processing and averaging options that I’m not even smart enough to list, much less describe.
And of course you can use Photoshop but it only works on files after they’re processed from RAW. The old school way is by adjusting layer opacity once the frames are loaded into the layer stack. The bottom layer is at 100%, layer 2 is at 50%, three at 33%, 4 at 25% and so on. The result is the average of all layers. The modern approach is lo load the layers into a smart object and then choose a smart object stacking mode of Mean or Median. Mathematically the Mean stack mode is identical to adjusting layer opacity.
For noise reduction I’ve found comparable results frame averaging in camera versus processing in C1 and then stacking “finished” frames in PS. Stacking in PS is more hassle but does offer some flexibility advantages. If you’re using averaging in lieu of ND filters then doing it in camera can provide the advantage of continuous capture whereas individual frames will always have a time gap.
For star trails I simply load the frames into the layer stack and change all of their blending modes to Lighten, no smart object needed.