Question UPAS - backlash?

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05 Jul 2025 04:16 #1399 by dunk
UPAS - backlash? was created by dunk
Hi,

I'm having a lot of difficulty getting the UPAS to align (using NINA/3PPA). The Altitude seems to work perfectly, however the Azimuth seems to jump around a lot.

If I nudge +1 at a time slowly, then I see no real updates in alignment. If I nudge +1 rapidly it overshoots. It's almost like there is backlash in the device - could this be the case?

I'm completely unable to use the automated NINA plugin as it times out before alignment is reached (because of the above issue - I assume the plugin nudges very slowly).

I'm using Gear Ratio 2, Speed 1000 as recommended in the manual/guide. My mount is a Rainbow Astro RST 135E.

I noticed someone else on these forums complaining of a similar issue.

As I say, Altitude works perfectly - its only Azimuth.

Any help or suggestions very greatfully received.

Cheers,

Duncan

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07 Jul 2025 15:29 #1401 by Stefano82
Replied by Stefano82 on topic UPAS - backlash?
How much is the backlash noticed?

Due to the mount setup weight, on the Altitude axis the backlash is basically null. On the Azimuth the backlash doesn't depend on the load but on the gears mechanic assembling. A minimum amount is required to allow the movement. The Backlash compensation can be calculated and easily compensated via software.A rough alignment within +/- 6° from the Polaris is suggested, being out of this range would prevent the alignment.

Stefano
Avalon Instruments Team

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11 Jul 2025 23:05 #1402 by dunk
Replied by dunk on topic UPAS - backlash?
I'm not saying it is backlash - just the behaviour I am observing where moving small amounts seems to do nothing, but then larger amounts overshoots. Specifically if I tap +1 for example 10 times quickly it will overshoot. If I tap +1 slowly waiting for the movement to finish each time it will not move enough. This makes the "automated" part useless in NINA because it of course taps slowly...

Could it be the gear ratio and speed? I am using the recommended values (ratio 2, speed 1000) and I have tried changing these without any noticeable difference.

Again this is Azimuth only - Altitude works perfectly as-expected.

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15 Jul 2025 09:27 #1404 by Stefano82
Replied by Stefano82 on topic UPAS - backlash?
It may be the Azimuth axis fixing a bit too stiff. You can try to ease a little bit this axis, this adjustment can be done or by releasing the Azimuth adjustment screw (see attachment) or releasing a little bit the three bolts on the UPAS bottom.
Please note that if you are planning to release the Azimuth adjusting screw, proceed by performing very little screw turn.
Best regards

Stefano
Avalon Instruments Team

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15 Jul 2025 23:46 #1406 by dunk
Replied by dunk on topic UPAS - backlash?
thx Stefano,

I don't see the attachment you mention.

Regards,

Duncan

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16 Jul 2025 08:44 - 16 Jul 2025 08:46 #1407 by Stefano82
Replied by Stefano82 on topic UPAS - backlash?
Hi Duncan
Sorry, it may have gone missed while posting.
Here it is
Best regards
 

Stefano
Avalon Instruments Team
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Last edit: 16 Jul 2025 08:46 by Stefano82.

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