CAA Questions: Page 5 - ZWO User Forum

CAA Questions

Moontanner

[unknown] Because I'm using a 2600Duo with a long focal length (4m) which often makes difficult to find guide stars. As a consequence meridian flip often leads too to a zero guide star field.
So, one I've found an acceptable guide star at the beginning of the session I'd like to find it back after meridian flip.

To do i've chosen "CCAA Return to Initial" (+360° rotation allowed) in Autorun menu. When meridian comes CAA rotates well to the initial angle BUT my new field suffers from a significant X+Y shift. Before CAA I used to have a perfect realignment after the meridian flip (with a 180° rotated image, so).

4m FL. Wow! That's getting up there. What scope are you using?

If you want the CAA to stay put during a meridian flip you need to limit the range of motion to 180 Deg. Given that every stacking program I've ever used accounts for the 180 Deg flip after meridian, I can't see any reason for the 360 option to be included as the default option in ASIAIR.

There are a few other quirks with the ASIAIR and the CAA that depend on the initial setup and type of mount you're using. I'm only using mine on a Esprit 120 @862mm FL and haven't had enough good weather tune up my 10" SCT @ 2500mm, so I can't help much with your question about the image staying on target. Maybe try hitting up Luxo for some advice on longer focal length scopes, although I'm pretty sure he gave up and ditched the CAA all together some time ago.

For the record, my CAA has been behaving itself for sometime now. The esprit 120 and 2600MM work well with the ASIAIR/CAA and stay fairly well centred on a target over various sessions.

All the best. Clear skies.

serge.llorente

Thank you very much for your reply. I'm using a C14 indeed... And yes I read here and there that limiting the range to 180° was preventing the CAA from movingbut when I tried it didn't. Well, maybe I was tired so I'll try again if it works every time with you :-) Yet this 360/180 option is a bit weird to me as at the end of the day there's no angle you can't reach a 180° limited move ? Happy to hear Luxo's advice too ! In the meantime i spoke with two other guys who eventually ditched the CAA too :-( Thanks again

Moontanner

serge.llorente

I see why you'd be having fun finding a suitable guide star at times with that scope and camera combo. 4000mm FL at F11 must be making the Duo work for It's supper.
My setup seems like a fast wide angle affair when compared to your beast.

Having tested the 360 deg limit option that keeps the image from flipping, it's simply too risky for my liking. It works except that the danger of cords getting ripped out is too great with the current software release.

I also found that my ASIAIR's centring routine can end up a fair way off at times which I imagine gets annoying at FL 4000mm.
My last two sessions had really good seeing for my area and I lost around 35 to 70 pixels in the x and y after the flip. A great result compared to some sessions.

I hope you get it figured out.
Clear skies.

serge.llorente

Thank you for your feedback. I fully agree with the risk of cable management with 360° option. It happened to me once and I barely tried the device a few times ! ZWO should manage this by "keeping in memory" the previous moves and never exceed 360° move whatever the angle requested. More importantly is the fact the centering routine reacts sort of randomly with CAA activated and this is definitively something I can't stand. So I guess I will only switch the CAA each time I'll need to rotate the camera and then switch it off. But considering the device has been released nearly 1 year ago I think we shouldn't be still facing such severe issues... Cheers

Moontanner

serge.llorente
My pleasure. I had a really frustrating start to my CAA adventure and can relate to your confusion/frustration.
I couldn't agree more with ZWO needing to get their act together on the CAA's occasional erratic behaviour. The outcome of the CAA over-rotating is almost always catastrophic.

If you haven't seen Luxo's evolving manual yet it's definitely worth a read. Find it here:
ASIAIR & Smart Camera
ASIAir: The Missing Manual
https://bbs.zwoastro.com/d/25890-asiair-the-missing-manual

Or over on Cloudy nights for a more robust discussion.

More importantly is the fact the centring routine reacts sort of randomly with CAA activated and this is definitively something I can't stand.
I'd love to know the specifics of how the ASIAIR decides an object is centred. Surely that's the parameter that's throwing things off at longer focal lengths? (The CAA just adds the possibility of a little more deviation from true centre IME).
I was looking at my guide logs from the last couple of sessions and the minor shift in centring lines up very well with my RA needing a little bit of work. All the persistently bad weather gave me time to do a complete rebuild on my mount, so I'm pretty close to as good as it gets in that regard.
The main shift in centring is definitely introduced after a flip or starting a new session. It's bad enough at 862 FL when combining multiple nights of Mono data and losing multiple galaxies due to necessary cropping of the final image.

All that being said, I really like having the ability to frame multiple targets during one evening while I'm tucked up in bed. It would be very hard to go back to manual framing.

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