Dithering in RA Only - Forums

Topic starter

Jul 31, 2023

Hi all,

I imaged the Running Chicken Nebula last night and my stack is plagued with walking noise. Due to this (and previous occasions of walking noise), I have been thinking about dithering, but as I own a Sky-Watcher Star Adventurer I can only dither in RA.

Are there any benefits of dithering in only RA? I did read that it actually causes issues instead of helping to reduce walking noise unlike dithering in both axies. I am almost ready to get a new mount which will be able to dither in both axies instead of my Sky-Watcher Star Adventurer.

If it is worth it to dither in RA, how would I go about it? I know I can use my ASIAIR Pro to setup dithering, but I use a remote shutter for my Canon 6Da. I do temporarily connect it to my ASIAIR Pro when I polar align, but after that I disconnect it and then switch over to using my remote shutter. Would I need to keep my 6Da connected to the ASIAIR Pro to be able to utilize dithering, or is it possible to dither it without my 6Da being connected to my ASIAIR Pro?

Zak

Engaging

Boyan Stiliyanov

Jul 31, 2023

I've had the same problem with walking noise.
I'm more of a practical guy and on the field, so I do it the old-fashioned way and just move a tiny bit my composition in both axes.
I do this manually atleast 4 times during my whole session, so it averages out later in stacking and it works atleast for me.

Of course there is a better way to do it with automated features of ASIAIR, but that's the way I do it

Wim van Berlo

Jul 31, 2023 · Edited: Jul 31, 2023

Unless your polar alignment is spot on, you will always have a natural drift in DEC. So, if you dither in RA only, you should be fine.
Consider this scenario; suppose you could dither in both directions, and you had zero polar error. Dithering would get rid of walking noise. When you stack, you could put your subs in order of increasing DEC. this would simulate a polar misalignment, and a random RA dither. But you would still have no walking noise. In other words, if you have some DEC drift, then dithering in RA should work. Just make sure that you dither enough in RA. And of course, your polar misalignment shouldn't be so large that you get elongated stars.
The problem you have is that you don't have any automation. If you want to dither, you would have to stop your sequence and your guiding, move RA, and start guiding and the sequence again. My advice, try to connect your camera to the asiair, and let the software do the job.

cs,

Wim

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