Dither if you can

For a better, smoother background sky…. Dither if you can.

So midway through last year, I stumbled on several YouTube videos touting the benefits of Dithering. I’d been living in my little world, just doing my AP, struggling with the usual demons (weather, wind, guiding, focus, etc.) and getting the usual results. I had no clue what dithering was or what the advantage is. Hmmmm.

So I checked the acquisition software I usually use (SGpro & SkyX) and holy smokes, dithering routines were built in and ready to configure and run. So with just a few clicks I had it pretty well set up. So the next decent sky, I enabled dithering and after getting over a few little “gotchas”. it started running smoothly. The next morning I did the initial processing and well… I was floored. The usual struggle with background noise just gone! What a pleasure to process when the background noise was so quiet and uniform.

There is lots of information on the web about how dithering works and what are reasonable settings. Much of the information gets technical quick and you might lose sight of the basics of how dithering does its thing, and how it helps.

How is dithering done? The basic method is that during the imaging session, the scope is randomly moved off your set target by a few arc-seconds between image frames. This is done typically by your guide software but I suppose it could also be done with a great mount (optical encoders et al). The result is that when you stack the set of images, stacking software aligns frames by the stars in the image field (i.e., your target) and in doing so the background sky shifts slightly between frames. The effect is the “noise” of the background becomes blurred and averaged out. I you haven’t tried it, DO.

Here’s a couple from last year:

NGC-891
ASI533 clr camera, Taken Oct 30,2021 from Badger Observ.

Horsehead +
ASI-533 clr camera, 11-13-2021, Taken from the Badger Observatory

I think using dither really works to smooth and clean up my images.

al

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