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Old 11-12-2020, 06:32 PM
Saturn488 (Chrys)
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Exclamation SGP HFR Issues

I was out imaging last night, very clear and nice as well!

Using an ASI178MM-Cool on an ES102 with an EFW LRGB ZWO filters using Sequence Generator Pro. My auto focus works perfectly but having issues getting really sharp focus. I was able to get it down to 2.5-2.8 on the red filter but on the blue it went up to 3.8 and looked blown out. Also the images came out brighter as well.

I made a list on what it could be.

- Seeing conditions (it was pretty consitent all night, it can't be that)
- Telescope tube (doubt it)
- Filters (very possible, maybe the wrong way around?)
- Camera (probably not)
- EAF (I did check focus)
- Guiding (no as the guding curve is nice and flat and the object remains in the FOV).

Red looks ok, Blue way out of focus and very bright, Green a bit out of focus and bright too.

Also to note my HFR varies. While taking 6 second subs when framing and focus m HFR value will go from 1.08 to 1.35 to 1.14 to 1.10 and to 1.28. There will be sudden jumps (not guiding).

Any idea where my issue may lie?? I am going to check the orientation of the filters now.
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Old 11-12-2020, 07:00 PM
sunslayr (David)
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Kind of sounds like its smoke or ash in the air, got any burnoffs in the area?
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Old 11-12-2020, 07:30 PM
Saturn488 (Chrys)
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Quote:
Originally Posted by sunslayr View Post
Kind of sounds like its smoke or ash in the air, got any burnoffs in the area?
Not that I know off.

I forgot to upload the photos.

First one is Red Filter, Second Green Filter, Third Blue Filter.
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Old 11-12-2020, 07:38 PM
sunslayr (David)
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Are you using filter focuser offsets with your filter wheel? As far as I know the ZWO filters are not parfocal.
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Old 11-12-2020, 08:11 PM
Saturn488 (Chrys)
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Quote:
Originally Posted by sunslayr View Post
Are you using filter focuser offsets with your filter wheel? As far as I know the ZWO filters are not parfocal.
Not offsets no, I might have ato look into that tonight.
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Old 11-12-2020, 11:39 PM
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Atmos (Colin)
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I believe there may have been some high level cloud around last night, at least that is what was showing up on the cloud forecast! Not that I really trust it haha
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Old 11-12-2020, 11:59 PM
Saturn488 (Chrys)
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I believe there may have been some high level cloud around last night, at least that is what was showing up on the cloud forecast! Not that I really trust it haha
Hard to tell sometimes isnt it!
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Old 12-12-2020, 12:27 PM
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The_bluester (Paul)
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The other bit if the filters are not parfocal, you might be better to autofocus on filter change, through the actual filter in use. For RGB the expsoure times would probably not need to be too excessive.
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Old 12-12-2020, 01:32 PM
Saturn488 (Chrys)
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I swapped the blue filter around and looks like I am getting really similar results now to the other ones which is good news. I got a feeling it was the wrong way around.

I think the HFR values im getting now is due to light pollution/seeing conditions and quality of filters being used.
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Old 13-12-2020, 09:49 AM
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Another thing to bear in mind is that just because the seeing is consistent, doesn’t mean it’s consistently good...it can be consistently poor too

I’ve often compared subs between subsequent nights (on extended runs of the same object) and the FWHM/HFR can vary quite noticeably.
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Old 13-12-2020, 10:48 AM
Saturn488 (Chrys)
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Originally Posted by Camelopardalis View Post
Another thing to bear in mind is that just because the seeing is consistent, doesnít mean itís consistently good...it can be consistently poor too

Iíve often compared subs between subsequent nights (on extended runs of the same object) and the FWHM/HFR can vary quite noticeably.
Amazing to think that you can have a thousand dollar setup or a 20k setup and you will always be limited by the weather.
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Old 13-12-2020, 12:50 PM
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The sky is the limit
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