ZWO 7X2 Filter Wheel Issue

The other night I was imaging remotely and when I awoke in the morning to inspect the subs, many subs were totally out of focus. The seeing wasn't good that night, but not that bad! I thought I may have a problem with the Sesto Senso 2 focuser.

Tonight the same thing happened, only the seeing is good. When the filter wheel changed to the green filter, all of the green subs were out of focus, whereas the Luminance and Red subs are fine. I manually changed the filter wheel to the green filter (even though it was supposedly already there) and suddenly I could achieve focus both manually and automatically.

When I installed the 7 filters at home I was very careful to make sure they were snugly screwed into their respective slots. I am now almost sure there's some kind of issue with the filter wheel, but not sure if it's an installation issue or a defect in the filter wheel itself.

Anyone have any experience like this?

Thanks,
Jerry

thats happen to me because the filters i use are from different brands and they are not parfocal , every filter have a different focus point

Is this a sudden change? Is it working ok if you do an autofocus after each filter change?

I use the same filter brand for all 7 filters. The problem might be resolved (I'll know tonight) by switching the filter wheel driver to UNIDIRECTIONAL only. This means the filter wheel always travels in the same direction when changing filters. Using OMNIDIRECTIONAL could introduce some slight errors alignment, I guess sort of like backlash. That may be the source of the problem.

Do you use filter offsets? Perhaps redo your filter offsets.

Jerry Gerber:
I use the same filter brand for all 7 filters. The problem might be resolved (I'll know tonight) by switching the filter wheel driver to UNIDIRECTIONAL only. This means the filter wheel always travels in the same direction when changing filters. Using OMNIDIRECTIONAL could introduce some slight errors alignment, I guess sort of like backlash. That may be the source of the problem.

Bad alignment would cause vignetting but not bad focus. Even though your filters are the same brand don't expect them to be parafocal. Even filters that claim they are won't be exact. A lot depends on the optical system as well. The best solution would be to determine focus off sets for all of your filters. If you are using something like NINA it's very easy to do this. Once you've set it up it will be automatic and transparent.

Tony Gondola:
Jerry Gerber:
I use the same filter brand for all 7 filters. The problem might be resolved (I'll know tonight) by switching the filter wheel driver to UNIDIRECTIONAL only. This means the filter wheel always travels in the same direction when changing filters. Using OMNIDIRECTIONAL could introduce some slight errors alignment, I guess sort of like backlash. That may be the source of the problem.

Bad alignment would cause vignetting but not bad focus. Even though your filters are the same brand don't expect them to be parafocal. Even filters that claim they are won't be exact. A lot depends on the optical system as well. The best solution would be to determine focus off sets for all of your filters. If you are using something like NINA it's very easy to do this. Once you've set it up it will be automatic and transparent.

I do autofocus immediately after every filter change. That works best for me.

Certainly an option, it just eats up more imaging time if you have a lot of filter changes.

Tony Gondola:
Certainly an option, it just eats up more imaging time if you have a lot of filter changes.

True, but it ensures good focus for each filter. Also, sky conditions are continually changing, a 2nd reason to focus after a filter change.

When I first got mine and temporarily had screw in filters (Chroma) if screwed in all the way, they would literally drag sometimes when rotating. I had to actually loosen them to make them fit. Chroma's are a bit thick, but… make sure your filter wheel, say at some angle(s) of operation, are not failing to turn properly.

Linwood Ferguson:
When I first got mine and temporarily had screw in filters (Chroma) if screwed in all the way, they would literally drag sometimes when rotating. I had to actually loosen them to make them fit. Chroma's are a bit thick, but... make sure your filter wheel, say at some angle(s) of operation, are not failing to turn properly.

When I installed the filters they seemed to fit perfectly, I tightened them snugly but not too tight. I recalibrated the EFW and switched to Unidirectional--I am hoping this resolves it.

Everything seems good now. I switched the filter wheel driver to UNIDIRECTIONAL and re-calibrated as well, EFW behaved as expected last night.

Jerry Gerber:
I use the same filter brand for all 7 filters. The problem might be resolved (I'll know tonight) by switching the filter wheel driver to UNIDIRECTIONAL only. This means the filter wheel always travels in the same direction when changing filters. Using OMNIDIRECTIONAL could introduce some slight errors alignment, I guess sort of like backlash. That may be the source of the problem.

I had that problem of using omindirectional wheel drive, but it rather creates donut shapes in your flats that play out badly on the image - not so much defocussing

Arny

Arny:
Jerry Gerber:
I use the same filter brand for all 7 filters. The problem might be resolved (I'll know tonight) by switching the filter wheel driver to UNIDIRECTIONAL only. This means the filter wheel always travels in the same direction when changing filters. Using OMNIDIRECTIONAL could introduce some slight errors alignment, I guess sort of like backlash. That may be the source of the problem.

I had that problem of using omindirectional wheel drive, but it rather creates donut shapes in your flats that play out badly on the image - not so much defocussing

Arny

Yeah, I'm really not sure why the stars would get defocused if the filter wasn't precisely lined up but the problem seems to be gone now. If it returns I'll have to hunt for other causes...

Related discussions