Ok, this is about a project - and it's about ENCODERS!

[skround]

Hi everybody! Newbie here in the forum faithfully in need of some advice.

Myself and some fellow astronomy club members are building a 0.8m telescope for an observatory.
For tracking accuracy encoders are key to detect the position of the telescope mount - you can think of that as a 2-axis machine.

Now the accuracy to take nice pics of the sky -and to do some science with that- translates into a linear accuracy of an incremental encoder of 0.3micron or better.

There are 2 main round surfaces that rotate with the axis and they are/will be ground to -hopefully- less than 0.01mm run-out.
The idea is to attach linear scales to these rotating surfaces and utilize an encoder.
The challenge is to do that on a budget i.e. buying used components.

For example I just bought a used RGH22 – it was too cheap not to buy it and just having a closer look at that.
To start with a silly question: can a Renishaw encoder work with a different linear scale as specified?

Again on linear scales – can it be salvaged from machinery? Is it as ‘expensive’ as the encoder or it’s the cheap part of the equation? I would probably need in excess of 1m for each axis. On ebay it looks like you can find encoders for less than £100 but there aren’t many scales…

Btw the motor control sys is already there and has convenient phase A & B inputs.

Thanks in advance!
Michele