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Question about Wanderer ETA and multi-night registration

Aries Productions Astro Pixel Processor (APP) Flattener Registration Tilt
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jpsc01 avatar
jpsc01 avatar

Hi everyone,

I don’t have the WandererAstro ETA (Electronic Tilt Adjuster) yet, but I’m seriously considering it and I’ve been thinking about a possible side effect.

As far as I understand, the ETA adjusts each corner of the sensor independently. This of course helps reduce tilt, but at the same time it also means the effective backfocus seen by the field flattener may change slightly (since some corners are pushed/pulled more than others).

👉 My concern is:

  • If the ETA converges to slightly different positions on different nights, wouldn’t that effectively present APP (or any registration software) with a slightly different optical system each time?

  • APP assumes the optical train is stable. But if the backfocus varies by a fraction of a millimeter, the flattener’s correction is not exactly the same, which could mean residual distortions in the corners differ from night to night.

  • This could make multi-night registration (and especially mosaics) trickier, since APP would need to reconcile images from “not-quite-identical” optical setups.

My current thought is that maybe the best workflow would be to:

  • find an “optimal” solution with the ETA,

  • lock it down, and only re-run the automatic tilt correction if there’s a real change (e.g. after a mechanical adjustment or a problematic meridian flip),

  • rather than recalibrating tilt every single night.

Since I don’t yet own the ETA, I’d love to hear from people who already use it:

  • Have you noticed this effect when stacking across multiple nights?

  • Does APP (or PixInsight) handle it gracefully, or can you actually see differences in star shapes across sessions?

Thanks a lot for sharing your ideas

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Alex Nicholas avatar
Alex Nicholas avatar

You wouldn’t adjust your tilt every night. Like, set and forget.

You would use it in place of the tilt plate on the camera. Get it flat, and do it again in maybe 6 months.

Alfonso Caschili avatar
Alfonso Caschili avatar

Tilt calibration with the ETA is still a partly manual process and requires some care and time. Also I don’t see much reason to recalibrate once you have found a valid solution for your system.

I have some rotation induced tilt and what I have done is to store two presets for 90 degree rotated fields and use the most appropriate one for the targets.

Still there’s not (AFAIK, unless it has been introduced in the past few weeks) a way to apply the presets from NINA in a sequence, so I have to setup the system before the night.

Regarding your backfocus question: if you have enough travel left after your tilt adjustments you can move the whole setup back and forth and this helps fine-tuning your BF. If you have a known distance you want to respect you can adjust your corrections so that the center of the field is at that specific distance.

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Tony Gondola avatar
Tony Gondola avatar

If you are having to correct for different degrees of tilt every session then you have larger problems that need to be addressed first. Tilt correction should mostly be a one and done process, like collimation. Unless your system is really bad, the magnitude of most tilt adjustments are going to be so small that I doubt that it will effect your back focus to a significant degree.

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jpsc01 avatar
jpsc01 avatar

I agree with the previous comments – I know I’m really looking at a bit of a corner case here.

That said, I do think there are situations where re-running a tilt removal in a NINA sequence makes sense, such as after a meridian flip (since the optics always shift a little), or when moving to a new target with a different rotation angle – especially with a refractor that isn’t perfectly collimated.

I also assume it shouldn’t be too hard (if it isn’t already the case) for the ETA software to weight the corner offsets so that the average backfocus relative to the field flattener stays stable, instead of effectively changing the spacing while removing tilt.

And I expect that the developer of Hocus Focus will likely collaborate with the ETA team to make this process more seamless and eventually fully automatic within a NINA sequence.

Overall, it’s really exciting to see the progress being made in this area, especially with the advent of Hocus Focus, which is clearly pushing the field forward.

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Tony Gondola avatar
Tony Gondola avatar

I think it was Cuiv, the lazy geek that was able to hack the device so that all three tilt adjusters could be made to work in unison, effectively using the unit as a focuser. Maybe that opens up a few possibilities you haven’t thought of?

That said, I still think that if things are changing that much after a flip then that needs to e addressed first.

jpsc01 avatar
jpsc01 avatar

Tony Gondola · Aug 31, 2025 at 04:01 PM

I think it was Cuiv, the lazy geek that was able to hack the device so that all three tilt adjusters could be made to work in unison, effectively using the unit as a focuser. Maybe that opens up a few possibilities you haven’t thought of?

That said, I still think that if things are changing that much after a flip then that needs to e addressed first.

yep, I agree. the fact is I’ve not been able to solve a random lens swift on a DSLR like objective (again a corner case :))
anyway, I think I’m going to play with this ETA in a near future, what I like the most is to be able to swap the same imaging train for different optics on an easy way

Lynn K avatar
Lynn K avatar

I think you are considerng possible problematic outcomes that are not the result of chip tilt.

It is when the chip has tilt that the corners will all be at different focus. When tilt is corrected or orthogonal with the focus plane all corners are equal distance to the focal plane. Yes, back focus may then need readjusting. But that should be once and done process.

If tilt occures after meridian flip, then there is a problem with focuser flexing, not the camera chip flexing. If your camera chip flexes after a meridian flip, you need to return the camera to the manufacture. The above is also applicable to slewing to a new object. If the whole camera is flexing, then that problem needs to be corrected.

Tilt correction should be viewed as a once and done process. However the tilt adjuster needs to remain in place. If removed, it will need to be readjusted.

Tilt is most often a result of poor chip adjustment by the manufacture, but can be caused by any part of the imaging train and more likely apoor focuser. Adjusting tilt further down the imaging train is more difficult, because each tilt adjustment results in a larger result of angle adjustment. This can cause the focal plan to be off center.

Tilt is a mechanical issue and needs to be corrected mechanically. The only software solution I'm aware of is BlurXTerminator. It seems you are trying to correct flexing in your camera/focuser train system with an automated tilt corrector. Good luck. Yes, that approach will more likely result in incorrect back focus.

Lynn K.

jpsc01 avatar
jpsc01 avatar

That s a valid point Lynn

Especially what you said about focal plan to be off centered where the ETA can give only orthogonality and certainty not centering