Dithering without autoguiding

lionel

Hello

With the last cmos camera we can use short exposure and so often we don't need to do autoguiding but dispite this it is always necessary to do dithering.

With asiair pro can you tell me if it is possible to do dithering without autoguiding

Thanks

PMTeam@ZWO

Lionel wrote:

Hello

With the last cmos camera we can use short exposure and so often we don't need to do autoguiding but dispite this it is always necessary to do dithering.

With asiair pro can you tell me if it is possible to do dithering without autoguiding

Thanks

Hello Linel,

Added to the todo. Could you explain to us more about your usage on Dither w/o Guiding?

lionel

Hello,

I see two situation where it is useful.

If you use a very accurate mount (10 micron, Ioptron with encoder, EQ8 RH ...) you don't need to use autoguiding but if you want to increase the SNR you must regularly shift the image on the sensor so you need dithering.

If you use a more comon mount (azeq6 ...) without autoguiding the periodic error causes the image to move on the sensor but this movement is slow and not random so it's not good and it is better to use dithering.

Lionel

PMTeam@ZWO

Lionel wrote:

Hello,

I see two situation where it is useful.

If you use a very accurate mount (10 micron, Ioptron with encoder, EQ8 RH ...) you don't need to use autoguiding but if you want to increase the SNR you must regularly shift the image on the sensor so you need dithering.

If you use a more comon mount (azeq6 ...) without autoguiding the periodic error causes the image to move on the sensor but this movement is slow and not random so it's not good and it is better to use dithering.

Lionel

Thank you, got it.

nickastro

I'll add to this myself: Pure software dithering without autoguiding would improve the stacked images for EAA sessions for sure.

I was processing a .ser video on Autostackert yesterday, for solar imaging (ASI178 used) and I tried the same stacking with and without software dithering available in Autostackert. The difference in noise was very significant!

It could be added as a simple tickbox on the live stacking options menu 😀
Nicos

comete83

Hello everyone,
As a future user of an ASI294MC Pro camera (ordered but that I'm expecting) I would like to add my 2 cents to this discussion. The choice of short exposures could also arise from the moving of the target, a very common situation when imaging comets with the small pixel sampling induced by CMOS pixel size.
For such situations guiding is not possible on the comet using an OAG !
As a result, short exposures in AutoRun session is required and being able to image with dithering would be a really a great feature.
Can we hope to see this feature coded in the near future ?
This would be a nice good resolution for 2021 😃
Thank you very much for your answer !

guitarmaker

Yes, I would also like to try dithering without auto-guiding on my ASIAIR Pro! I have a very good tracking mount - an iOptron CEM60-EC and it's RA encoder seems to be fighting the settle time after each dither. My settle time is only about 1 second in DEC because there is no encoder on the DEC which is super fast. But the RA settling takes about 30 seconds on average! With my f2 Hyperstar 11" Edge scope that is wasting a whole bunch of imaging time. I could just not guide at all but proper dithering is super important to a stacked image! The ASIAIR would need to dither and wait say 5 to 10 seconds then start another image (without guiding) it might work until iOptron fixes the issue with firmware?
I realize it isn't exactly ZWO's problem... Thanks!

735z4pr0

Software dithering without guiding is one of very good features of the latest years for enthusiasts of assisted sky observation... very strange ZWO didn't implemented yet.
I hope this will come in quickly... instead I'll look forward to change Asiair with other hardware/software that give me more satisfaction with less effort and less money :-)

BIGguiX

software dither please ! dont worry, i'll still buy a guide scope <3

nils

I’d like to contribute an example of why dithering without autoguiding would be really useful.

Recently, I imaged the Great Orion Nebula using a ZWO ASI585 (fantastic little camera!) with 10-second subs. I collected about 450 unguided frames -- at that short exposure time, guiding isn’t really necessary. With my setup, anything longer than 10 seconds blows out the core, so short subs were the only option. I’ve included the processed result below the over-stretched image, which highlights the artifacts: The image turned out nicely overall, but you can clearly see that the lack of dithering introduced a lot of fixed-pattern noise. :-(

That’s why I think it would be fantastic to have an option in the guiding setup like a simple checkbox:
"Enable dithering even when autoguiding is off."

This would make a huge difference for people shooting short, unguided exposures. Thanks for considering it! Also, as many people said in several forum posts, unguided dithering is standard amongst many other software for astro photography.

Astrop

Such a simple thing to implement, you'd have to include various movement range options probably best in sub arc seconds so the user can adjust based on imaging focal length, as there won't be a guide camera to measure in pixels (so direct override on the mounts tracking).

This feature is useful for camera body shooters whom want better accuracy than a star tracker or when using telephoto lenses, also helps people whom use cameras which aren't supported by the asiair. Id take a odd few images which are poor during a dither rather than not having the option to dither at all.

Also less equipment needed so again beneficial to those whom travel with their light camera body setups but want to use a proper equatorial goto mount so finding targets is also easier.