Swizerlan I use my eaf on different scopes so the focuser backlash is going to be different with each scope
Are you using a different EAF for each OTA? If so, you need not worry, since the backlash value is stored in the memory of the EAF itself, not in the ASIAIR.
What is the best way to measure eaf backlash while using asiair plus?
If you have a spring loaded micrometer, you can mount it temporarily on the OTA to detect changes in the drawtube; this is what I use:
This will allow you to measure the drawtube change per EAF step (you can get very accurate count by assuming the steps are linear, and watching the micrometer readings for a say, 200 EAF step change). You can then move the EAF step by 100 steps in one direction, and then 100 EAF steps in the opposite direction and see if you have come back to the same drawtube position. If not, the difference is the drawtube backlash and using the EAF scale that you had measured, be able to translate that into EAF steps.
Do this near infinity focus since the readings are not completely linear through a 360º EAF rotation (5760 EAF steps).
If you don't have the right tools, the easiest way to fake it, albeit taking more time, is to stick a piece of Gaffer tape to the focuser knob of your OTA. Then move the EAF by say, 200 steps one way and then N steps the other way, choosing N=50 to start, for example. If the focuser knob moves, it means the N is greater than the backlash. So, reduce the value of N to use as the new updated N, and repeat the experiment. If the focuser knob does not move, increase N and repeat the experiment.
Reset the EAF close to infinity focus each time, since the EAF steps is not linear (I had a year or two ago posted a graph of the nonlinearity of one of my EAF, you might be able to find the posting).
By doing this repeatedly, you will arrive at a value of N that is the backlash.
Chen
