Measuring tracking errors on an Equatorial Platform

[DIYman]

Hello all

I have an EP driven by a stepper motor that allows adjustments for small variations in speed and also for setting the solar and moon rate. The EP varies its speed throughout the start to finish cycle (about one hour). (I have taken into account possible issues with drop in voltage supply to the EP and ambient temperture differences.)

Rather than waste a good viewing night I would like to map the tracking speed of the EP on the work bench. I need to determine if the variation might be due to the curve of the the sectors driven by the drive rollers. Can anyone sugest how I might be able to map the tracking speed of the EP incrementally from start to finish?
Cheers, Doug.

[longly]

Hi Doug, I can,t directly help with your tracking error question, but I can point you in the right direction, having made my own platform.Join the EQ Platforms Yahoo Group, there,s all the help you need there if you post this question.Specifically, send an email to Nils Olof Carlin, whose address you can get off the net.He is a very approachable and helpful person, and one of the "gurus" on eq platforms and correcting tracking errors - in fact I think he has a program for stepper motors to correct exactly this.
Kind regards, Stewart Longly, Napier ,New Zealand.

[DIYman]

Thanks Stewart
I will contact Nils as sugested.
Cheers
Doug

[Shiraz]

maybe set up a digital verier caliper alongside the mount with the slide bar in contact with the moving part of the EP and along the arc of motion. Set it up with the caliper initially extended and manually log the position at fixed intervals to plot position against time as the slide bar is pushed in by the EP movement - the slope will give an estimate of the rate.

[DIYman]

Thanks Shiraz
I thought about using a dial gauge but with the top moving in a curve rather than a straight line makes me wonder if it is a solution. I suppose I could tie to the top part, a piece of string with a weight. The weight would hang vertically over the edge of the platform. As the top is driven I could measure the amount of vertical movement of the weight in discrete periods of time.