ZWO EAF Backlash Compensation 

This is the kind of video I love, i.e., practical advice, patient demonstration, and knowledgeable. Do keep your videos coming, they’re really helpful.

I like your DIY approach to determining backlash. I followed your logical method, though I used two pieces of tape, and it worked perfectly. Thanks!

Excellent, logical, easy to understand and can be done during the daylight!

Best description on how to set backlash ive seen yet! awesome 🙂

Awesome video. Just what i needed to set up my new ZWO focus motor. Tried it tonight and it worker perfectly. Focus was right on. Thanks, Mike

Merci depuis la France (proximité de Saint-Tropez) !

Thanks a lot, finally I understand how to calculate the backslash compensation. Regards from Chile

Nice clear teaching... thanks for making the video!

Very demonstration of how to determine backlash, without being under the stars :)

Very nicely done!!! Thank you.

That was a good demo of calibrating my new ZWO EAF. Subscribed. Looking forward for more content. Side note, smile a little, doesn't hurt.

excellent video, this is so helpful

explain very well thank you

I guess this is if you’re not using an entire ZWO setup ? Using ASIAIRpro and plus, zwo finder miniscope, and their eaf focuser with an old ioptron Zeq25gt, and an AT65edt scope, I am amazed at how my setup always get perfect focus.

thanks for the good explanation!

Thank you

Nice video, but one point I might add. Your method here is correcting the backlash in the ZWO gearbox and even in the fine/coarse gearing of the focuser, but does not take into account any additional backlash that exists in the rack and pinion of the focus barrel. To eliminate it 100%, you'd need to rig up a DTI or similar accurate device to measure the actual movement of the barrel. I'm pretty sure if you did that, you'd find that the relationship of the two knobs will not match - which is fine because ultimately they do not matter, only the position of the barrel matters.

Thank you very much for your video. It has been very useful to me.

this method of determining the EAF backlash is theoretical because you start from the premise that the mechanics of the tube have no backlash. it is best to measure the distance that the tube travels during repeated in and out movements.

Hello, Thank you for your useful video. I have just bought an EAF and now I am at the point to find the right value for the backlash. I just was about to do it like you, but then I asked myself if this is the right backlash I should look at? Isn’t your backlash the gap between the fine/coarse gear? The EAF if directly connected to the main axis and the low gear button is just moving, because the main axis is moving, but has nothing to do with the movement of the barrel. I think I need to look for the backlash in the EAF and (if present) between the worm wheel and the rack and pineon drive? I want to do this at the sky and see if I can go back to the same star diameter after focusing in and out. This might be more difficult, but show directly the effect of the right focus. And this method does not need any additional tool. What do you think about this? Regards Jens

So, the backlash you find with the ZWO utility, in NINA do you put it in the IN box or the OUT box? Thank you for your reply.

How about the backlash caused by the spring coupler?

Are you using the SV503 70mm Refractor ED ? I have the ZWO EAF with the SV503 70mm. I would assume that I could use your demo as a guide to set backlash with my rig? Also, is that your starting position "in focus " ? 20145 ?

Backlash should be done with your camera and filter wheel INSTALLED ! Why ? because the loading on your Rack and Pinion focuser will be affected by the weight / load. The torque / Current required to rotate the focuser will also change the backlash.