Measuring Backlash

[Entropy]

Hey Guys,

I recently purchased an EQ8 mount and when I used it for the first time noticed something which I think may be backlash (Not 100% sure, because I've never seen or had it before). What was happening was that it was taking a while, when autoguiding, for the mount to actually be moved even though there was guiding commands being sent to the mount).

I spoke to the store where I bought it from, they were very helpful, but said that I should update to 2.10 of the motor controller drivers before worrying about sending it in to them for adjustments. I only had 2.09 when I initially tested the mount and have now upgraded (3.35 on the hand controller). I was just wondering if there was any way, without taking the scope out and pointing it at a star, to test to see if my backlash has been reduced to a reasonable level? I do not have access to a car for a while, and live in the middle of Sydney so I can't test with actual stars.

This does not have to be quantifiable testing (although that would be good) just a yes or no to 'reasonable' backlash (I'm not even sure I know what that means though)

Thanks

[billdan (Bill)]

Hi,

I don't have an EQ8 but with my EQ6 if I have problems guiding it usually caused by either poor polar alignment or not enough steps set in calibration of the PHD software.

Backlash should not be any concern to you if you have the mount slightly weights heavy and slightly camera heavy so the RA and DEC spur gears are leaning on the motor gears.

If you are using PHD and set it to calibrate ( PHD should do this automatically on first switch on) you should be able to see star movement in your monitor, if not increase the step size, I have mine set on 1750mSec.

Hope this helps.

Bill

[jakob]

To check backlash, turn off tracking and point it to a terrestrial point, then use the manual controls to move the scope to the same point approaching from left and then from the opposing side while reading the encoder position on the hand controller.

The difference between the two readings is the backlash.
You should use reticule ep for this.

I wold be interested what the reading is. I checked my heq5 this way.

Regards, Jakob