ZWO CAA – Small rotational play affecting long exposures? - Forums

Hi everyone,

I recently installed the ZWO Camera Angle Adjuster (CAA) in my imaging train and noticed that even when fully tightened, there's a small but clear rotational play — I can gently rotate the camera a tiny amount by hand.

I contacted ZWO and was told “this is normal and won’t affect performance”.
But in my experience — especially with narrowband imaging, long exposures (300–600s) and focal lengths of 600–1000mm — this introduces real risks:

Micro-movement during exposure

Focal plane drift

Wind-induced motion

I’ve already removed the CAA from my setup and switched to a fully rigid configuration (M54 Tilter + backfocus adjuster), but I’m very curious:

➡️ Have you noticed this rotational play in your CAA unit?
➡️ Has it had any impact on your frames (even subtle)?
➡️ Do you still use it in your imaging train, or replaced it?

Feel free to share your thoughts or setups — I’d love to compare experiences.
Clear skies,
Cosmin

Hi Cosmin,

all the ZWO CAAs have the rotational play.
I have two units and use them up to 2500mm FL with full frame Camera. No issues on sharpness or star deformation caused by the CAA.

The drivers are still pretty shit risking clashes and cable snags especially when used with Filter wheel.
Until this is fixed, proceed with caution. This is true with ASCOM and ASIAIR.

ZWO had years to refine the software but feels like pre alpha stage. Yay, it moves is all it can at the moment. But these movements are pretty unpredictable.

The mechanics are quite good, except for the rotational play. Which at least in my three setups doesn´t have any noticeable impact.

Best regards,

Stephan

Stephan Linhart:
Hi Cosmin,

all the ZWO CAAs have the rotational play.
I have two units and use them up to 2500mm FL with full frame Camera. No issues on sharpness or star deformation caused by the CAA.

The drivers are still pretty shit risking clashes and cable snags especially when used with Filter wheel.
Until this is fixed, proceed with caution. This is true with ASCOM and ASIAIR.

ZWO had years to refine the software but feels like pre alpha stage. Yay, it moves is all it can at the moment. But these movements are pretty unpredictable.

The mechanics are quite good, except for the rotational play. Which at least in my three setups doesn´t have any noticeable impact.

Best regards,

Stephan

Hi Stephan,

Thanks so much for the detailed feedback — much appreciated.

You're confirming exactly what I suspected:
✅ The rotational play is a general characteristic across all units
✅ It might not impact everyone — depending on setup rigidity, focal length, camera weight, etc.
But also that the motorized control is risky, especially with ASIAIR or ASCOM.

In my case, I have a rigid train with a M54 tilter, and I mainly shoot narrowband with long exposures (600s) at around 900–1000mm.
That’s why even the slightest unintended rotation or focal plane drift becomes a risk I’m not willing to take — especially since I’ve seen minor star distortion in test frames.

I agree: the CAA has potential, but until ZWO improves both the mechanics (to remove the play) and the driver/software behavior, it's hard to trust it fully in a precision workflow.

Thanks again for sharing your experience — it really helps to know how it behaves in real-world imaging at higher focal lengths!

Clear skies,
Cosmin

I own two Optec 2" Pysix rotators. I also own a Pegasus Falcon v1 and the v2. There is "O" rotation slack in all. Any rotational slack/backlash error would be unexceptible to me. That would force me to improvise some sort of weight system to alway pull the rotater to one side. I can only conclude that when bringing a product in at a low price point, the perfromace will be compromised and for the manufacture to state such performance is normal.

The software is excellent in both the Optec and Pegasus. The repeatability is very accurate.

However, the Falcon V1 introduces extream tilt on my FSQ85ED. According to ASTAP tilt went from 4% at 0 angle to in the 40s% at 180 angle. I resorted to using the Tak manual CAA on the FSQ85ED. I have not tested the Falcon V2 yet.

Lynn K.

Lynn K:
I own two Optec 2" Pysix rotators. I also own a Pegasus Falcon v1 and the v2. There is "O" rotation slack in all. Any rotational slack/backlash error would be unexceptible to me. That would force me to improvise some sort of weight system to alway pull the rotater to one side. I can only conclude that when bringing a product in at a low price point, the perfromace will be compromised and for the manufacture to state such performance is normal.

The software is excellent in both the Optec and Pegasus. The repeatability is very accurate.

However, the Falcon V1 introduces extream tilt on my FSQ85ED. According to ASTAP tilt went from 4% at 0 angle to in the 40s% at 180 angle. I resorted to using the Tak manual CAA on the FSQ85ED. I have not tested the Falcon V2 yet.

Lynn K.

Thanks Lynn — incredibly helpful feedback.

You're 100% right: any backlash or slack in a rotator should be treated as a design flaw, not a "feature" explained away by the manufacturer. Your approach — zero tolerance for movement — is exactly the standard I wish ZWO had applied.

It's frustrating to see a product introduced with obvious mechanical compromise, and instead of addressing it properly, they just say it's normal and hope users won't question it too much.

The software point is also very relevant. It's not just about the hardware — predictable, accurate movement and repeatability matter just as much.

Interesting to hear about the Falcon V1 tilt on the FSQ85ED — wow, that’s a serious shift. Would love to hear how the Falcon V2 compares once you test it.

Thanks again for chiming in — the contrast between solid rotators and the CAA becomes clearer with every reply.

Glad my post was helpful. My Pegasus Falco V1 is well made and rotates very smothly and seems to be very accurate. By "seems to" I mean I did not not use it after the tilt problem. I never did mutible rotations to different targets over different nights.

My unit seems to have an orthogonality issue in the rotatiom mechanics to the moumting plate. Other units may not. But, I'm not going to buy several units to test and re-sale on Astromart. I also us a counter weight to off set the weight of a filter wheel. However , when testing the falcon V1 I was using a OSC.

Counter weight: You could use this to keep the slack in you rotater to one side.
astrohutech.store/product-category/d-imaging-accessories/counterweight-for-cfw/

I will be giving the Falcon V2 testing when the weather warms up. Rotaters are necessary to me, because I'm trying to totally automate my system. My Obseratory is onlt a short distance from the house. But I'm nearing 78 and working to be albe to do multible targets through the night while I sleep.

Lynn K.

Thanks again, Lynn — your insights are truly appreciated.

The orthogonality issue you mentioned on the Falcon V1 is a great reminder that even with good mechanical parts, alignment and consistency are critical. That 40% tilt you observed must have been quite a surprise — especially on an FSQ!

You're absolutely right about the slack compensation idea. I’ve seen the AstroHutech counterweight before — clever solution. But as you said, it’s a workaround. Ideally, the rotator should just be solid to begin with.

I totally relate to your goal — I'm also aiming for a fully automated setup where I can run multiple targets unattended. But for that, I need zero movement or unpredictability in the train. Until ZWO redesigns their CAA or improves tolerances, I’m keeping it out of my system.

Looking forward to hearing how your Falcon V2 performs once you get to test it. I hope it solves the issues from the first version!

Clear skies and thank you again,
Cosmin

I can vouch that the Falcon Rotator v2 is pretty solid. No slop or play that I can detect. And my tilt is consistent (and near zero) regardless of rotation position.

Only issue is that it does not play nice with NINA's rotation range limit – it has its own internal logic to prevent cable snags (it will not cross the 220 degree line, but will go on either side of that). This was confusing and worrying until I emailed their support and they explained it to me.

I have the Falcon V2 as well - no rotational play at all and no problems at all. Tilt is almost zero at all rotational positions. I just today got the ZWO CAA delivered - will be interesting to see how it performs. My Falcon V2 is mounted on the 12"Truss at 2500mm focal length - and as I said before - zero play, zero tolerance and 100% performance.

Georg N. Nyman:
I have the Falcon V2 as well - no rotational play at all and no problems at all. Tilt is almost zero at all rotational positions. I just today got the ZWO CAA delivered - will be interesting to see how it performs. My Falcon V2 is mounted on the 12"Truss at 2500mm focal length - and as I said before - zero play, zero tolerance and 100% performance.

Looking forward to hearing your thoughts on the CAA once you try it!

Since you’re already working with the Falcon V2 on a 2500mm setup, I think you’ll notice immediately how the mechanical tolerance differs. The play is subtle, but if your system is perfectly collimated and balanced, you may detect it with a filter wheel in place.

Please share your impressions after some testing — especially during long exposures. It would be great to have another direct comparison from someone with experience at longer focal lengths.

Cosmin Batica:
Georg N. Nyman:
I have the Falcon V2 as well - no rotational play at all and no problems at all. Tilt is almost zero at all rotational positions. I just today got the ZWO CAA delivered - will be interesting to see how it performs. My Falcon V2 is mounted on the 12"Truss at 2500mm focal length - and as I said before - zero play, zero tolerance and 100% performance.

Looking forward to hearing your thoughts on the CAA once you try it!

Since you’re already working with the Falcon V2 on a 2500mm setup, I think you’ll notice immediately how the mechanical tolerance differs. The play is subtle, but if your system is perfectly collimated and balanced, you may detect it with a filter wheel in place.

Please share your impressions after some testing — especially during long exposures. It would be great to have another direct comparison from someone with experience at longer focal lengths.

Hi again,
I have installed both CAA´s today on two of my systems - one on the Hypergraph6 (fl=420mm) and the other on my RASA11 (fl=600mm). I noticed that that small play exists on both new systems. It is very small, but if you touch the camera, you can feel it.
I am planning to examine the outcome first on those two systems at exposure times between 180 and 300seconds. I´ll get back once I have results...
CS
Georg

I have the CAA in my image train now for 2 nights. No problems at all at 2350 mm FL. I also noticed the play but as long as it doesn't affect the exposures I'm fine with it. I was thinking about a rotator for quite a while already but they were too expensive for me. So when I learned about the CAA I almost immediately bought it.

I'm using it with ASCOM and the driver is pretty bad. I was hoping for some max/min values since I'm using it with a filter wheel and I can only rotate it by 180°. So I wrote down the angles to which I can rotate without a crash and I made sure it rotates smoothly between these without any cable issue.

Georg N. Nyman:
Cosmin Batica:
Georg N. Nyman:
I have the Falcon V2 as well - no rotational play at all and no problems at all. Tilt is almost zero at all rotational positions. I just today got the ZWO CAA delivered - will be interesting to see how it performs. My Falcon V2 is mounted on the 12"Truss at 2500mm focal length - and as I said before - zero play, zero tolerance and 100% performance.

Looking forward to hearing your thoughts on the CAA once you try it!

Since you’re already working with the Falcon V2 on a 2500mm setup, I think you’ll notice immediately how the mechanical tolerance differs. The play is subtle, but if your system is perfectly collimated and balanced, you may detect it with a filter wheel in place.

Please share your impressions after some testing — especially during long exposures. It would be great to have another direct comparison from someone with experience at longer focal lengths.

Hi again,
I have installed both CAA´s today on two of my systems - one on the Hypergraph6 (fl=420mm) and the other on my RASA11 (fl=600mm). I noticed that that small play exists on both new systems. It is very small, but if you touch the camera, you can feel it.
I am planning to examine the outcome first on those two systems at exposure times between 180 and 300seconds. I´ll get back once I have results...
CS
Georg

Thanks for feedback Georg, can't wait to see your longer time exposures test, maybe even with a 600sec exptime?

Christoph Paulus:
I have the CAA in my image train now for 2 nights. No problems at all at 2350 mm FL. I also noticed the play but as long as it doesn't affect the exposures I'm fine with it. I was thinking about a rotator for quite a while already but they were too expensive for me. So when I learned about the CAA I almost immediately bought it.

I'm using it with ASCOM and the driver is pretty bad. I was hoping for some max/min values since I'm using it with a filter wheel and I can only rotate it by 180°. So I wrote down the angles to which I can rotate without a crash and I made sure it rotates smoothly between these without any cable issue.

How long the exposures are in your tests? Btw, the rotation limit option of 180 degrees is already in the beta version of AsiAir.

Cosmin Batica:
How long the exposures are in your tests?

300 seconds

Quick update after a few more months: With my Newtonian I can see the play in the spikes of very bright stars. I first shot the tulip nebula and didn't notice anything. Now I shot the veil nebula including 52 Cyg, which has very long thin spikes. After stacking I saw 2 different spikes on that star when zoomed in and I went into the subs and noticed that the spikes rotate a little bit after meridian flip. While it's not nice, it's not the end of the world since it only happens on my Newtonian with very bright stars. And the image looks nice anyway.

Mine too has play, but in exposures up to 300sec I have not noticed any issues. This is on a smaller refractor , SQA85 with a 294mm. My one bit of advice to anyone using it for the first time is to spend time rotating it and looking for interferences. I thought I had clearance when I first hooked it up, but ended up with subtle collisions. Also, allow for lots of extra cable to allow for winding. But it is superb for framing so far.

After some time I decided to use the ZWO CAA in my setup. I didn't notice any rotational impact in images, so far. I think that rotation play is normal and doesn't seems to affect the image.

Here's 52 Cyg where you can clearly see it. Like I said, only visible with a Newtonian on very (very) bright stars. And it's not a big deal in my view.
It only rotated during the meridian flip as the weight shifted. Of course it also depends on the weight, orientation, etc. It does not move when taking subs. So the weight/balance of the imaging train usually pulls it to one side.