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setting the backlash (HEQ5 pro)

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I'm going through the options of the EqMod driver and I see that you can set the backlash, now how does one set this up and what exactly would I gain from it please?

4 years 7 months ago #42321
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Eh, what do you gain from backlash correction? A corrected backlash I'd say ;^>
It's similar to the correction you can do in PHD2, just that there it is in ms, here it is in steps of the motor...
And similar to there, it's mainly useful for DEC
4 years 7 months ago #42330

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Backlash correction is very useful. I have one mount (not on Eqmod, but OnStep (which uses different units)) where I made the DEC worm wheel, and unfortunately, due to how I mounted it (great learning experience, btw) it's got severe backlash that PHD2 doesn't handle. If I set the similar OnStep setting (and turn off ignore backlash while guiding) then the mount can guide pretty well. Otherwise PHD2 refuses to calibrate. (That's an extreme example) On other mounts (again, OnStep) it is useful to deal with most of it, and to have gotos be very accurate.

It's one of the things that Meade ETXes like to do. (Though I don't use them with a computer.) When you slew it one way or the other, it's calculating and storing the backlash.

Quite possibly, a useful feature to add to standard properties/capabilities is a backlash setup, possibly with something to train it. I actually have something similar with my (DIY) focuser, where it takes about 72 (micro) steps to get moving. I would assume that other interfaces can expose it.

Hope that helps you or anyone else coming across the topic, good luck!
4 years 7 months ago #42352

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Typically backlash correction will make a quick motion to take up any gear slack when you change slewing direction. The value can be determined by setting the slew speed to the slowest setting and watching a star as you reverse the direction of your last commanded movement. Gradually increasing the backlash value until you notice the star jumps, then bring it back down until you find a value that gives a stable, delay free motion.
Bare in mind some mount's backlash settings to not play nicely with autoguiders, so every attempt should be made to minimize backlash mechanically first.
The following user(s) said Thank You: Jasem Mutlaq
4 years 7 months ago #42360

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Agreed, mechanical adjustment first. I recently made the error of letting the meridian flip checkbox cleared in Ekos (I suspect it is its default state but need to confirm).
As a result, the scope did rattle against the tripod for a few hours, and that friction caused the RA axis to develop a backlash of half a degree. With no change to its settings, PHD2 is not able to manage that new characteristic of the mount and fails calibration.
The backlash on HEQ5-Pro appears mostly because the adjustment screws around the axis erode or move. It is relatively easy to reduce it to acceptable levels after such an event occurs. I will need to check the inner gears at some point for sure, or send it for service, or review again PR #612. So many things and so little time...

-Eric
4 years 7 months ago #42573

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