Quote:
Originally Posted by pjphilli
Hi Rob
What is dithering and how does it improve stacking?
Cheers Peter
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Hi Peter,
I'm sure many could explain it better but here goes...
According to Stark-labs, 'dithering' is to slightly offset the guide position (say 0.5 pixels) from frame to frame. What is the advantage?
Say you have a dim star that unevenly illuminates only a few pixels. Even when several frames are stacked the star may appear out-of round. Now, if we 'dither' several frames by a random amount, the star will create a slightly different pattern of pixels for every frame.
When these frames are aligned (they must be aligned) and stacked, the uneven illumination should average out and the star should appear rounder.
It's worth mentioning that poor seeing, soft focus and inaccurate guiding can result in rough 'dithering' as well! I usually achieve dithering by these very methods.
However as my guiding accuracy and focus improves I am noting dim stars that illuminate only 3 pixels, so I'll be using PHD's dither feature soon enough.
Cheers,
Rob