7 replies to this topic

[acrh2]

Hi.

 

My ZWO EFW has developed a problem, which may or may not be new. 

I have LRGBSHO filters loaded, in that order. I have unidirectional setting turned ON in the ASCOM properties. I know this setting works because I can see that it takes a short amount of time to go one filter down the list, but a much longer time to go one filter up the list. 

 

Here's the problem. I have a sequence where I take a bunch of G subs, then a bunch of R subs. The beginning of R subs all have misaligned dust motes, until an autofocus kicks in which is set to work with L filter and filter offsets. After the autofocus is completed, all of the dust motes become aligned. 

It seems to me that there's a difference in position when switching from G->R and L->R, even though G->R does go through L position. 

 

Questions:

1)  Have you seen anything like this before? 

2) What is the fix?

3) If I run Recalibrate option from ASCOM properties, will I have to take new flats?

 

Thanks.

 

[DeepSky Di]

I dont understand - why are any subs being taken before the autofocus?

 

However with ASIAIR, I don't have filter offsets so I do have an autofocus before each filter. I can turn it off if the filters are parfocal.

[acrh2]

I dont understand - why are any subs being taken before the autofocus?

 

However with ASIAIR, I don't have filter offsets so I do have an autofocus before each filter. I can turn it off if the filters are parfocal.

Because my thinking is that with filter offsets, you don't have to refocus on filter change. In 2 years that I've had this filter wheel, it's never been a problem. However, I'm not sure if I ever had G->R in my sequence before, so I'm not sure about that anymore.

[JohnPancoast]

"I dont understand - why are any subs being taken before the autofocus?"

 

I think this would be my question as well. Autofocus before using each filter...

[pyrasanth]

If you recalibrate your filter wheel you will need new flats as they will no longer match your existing flats as they will rotate into different positions. I suggest you also put a small delay between filter changes- this will allow any bounce of the wheel to settle out. Also confirm that everthing is set to unidirectional in the ASCOM driver and nothing is over riding this setting & making the whell go bi-directional.

[sn2006gy]

If autofocus corrects this, then it isn't misalignment. Perhaps with slightly lower temps in northern hemisphere you need to calculate some minor offsets or focus on filter change (which is what i do)

[hyiger]

The whole point of the filter offsets is you have a reference filter, example 'L' that you auto-focus on first then other filter changes are just offsets from that number. Allows doing 'fast' sequences of 1 sub each of LRGB or SHO then loop. That way you can get all the channels in if your session time is limited,  clouds get in the way etc without having to pause for autofocus between the filter changes. Then set autofocus to kick in on 'L' once an hour, meridian flip and/or every 2C temp change. 

Edited by hyiger, 09 September 2024 - 10:17 AM.

[acrh2]

Maybe recalibration from ASCOM properties will fix it. 

Meanwhile, to avoid taking new flats, I'll just stick a filter change to L in between switching filters in a sequence, and make sure that I always switch to L then to the filter in question when taking flats.