Wednesday, January 18, 2017

Problems Stacking Canon T3i Raw Images With DSS

Figure 1)  Latest Image-M46 and M47

Figure 1 shows the latest image after processing with a work-around.  This post describes problems with stacking raw exposures I have with DeepSkyStacker.

DeepSkyStacker (DSS) is a wonderful stacking program especially when you factor in the price. Many astrophotographers start with DSS since it is free and many stick with it.  When I first began to use it a few years back with my raw exposures, it would only show a partial image on the view screen and not stack, however, when I put in jpeg exposures it would work.  After an internet search I discovered the Canon EOS Rebel T3i (600D) wasn't supported by DSS (3.3.2) and someone recommended converting the exposures to tiff format.  I did this using Digital Photo Professional and then stacked the exposures and everything was fine.

Last year I downloaded the latest version of DSS (3.3.4) as it supported the T3i/600D.  Note: In order to download the new version you have to download WinRAR file compressor and unzip the program to install it.  I stacked my raw exposures using the latest DSS and it seemed to work.  Figure 2 shows the autosave file generated by stacking the raw exposures.

Figure 2) raw exposures stacked in DSS 3.3.4

Upon closer examination the smaller stars look like pimples.  I tried re-stacking the exposures but the result was the same.

I converted the raw exposures to tiff format and stacked them using DSS.  The results were much better.  Figure 3 shows the autosave file generated by stacking the tiff exposures.

Figure 3) tiff exposures stacked in DSS 3.3.4

The results speak for themselves.  All of the stars appear as relatively sharp points as opposed to the diffuse splotches generated from the raw exposures.  

The conclusion is the new version of DSS still does not stack raw exposures from a T3i/600D and I will continue to convert raw images to tiff format.  At some point I may try another stacking program like Nebulosity, DSS still works pretty well although it does add a extra little time to stack.

I plan to do another test with my next image so I may have an addendum to this post.

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