A Step-by-Step Guide to ZWO EAF Backlash Calibration and Tuning

If you have a ZWO EAF (Electronic Automatic Focuser) this video will show you to use the ASIAir App to calculate and calibrate for the backlash of your telescope.
Note only the ZWO EAF is compatible with the ZWO ASIAir ecosystem, but the same theory shown in this video can be applied to other brand focusers using other apps and software.
Non sponsored affiliate Links for stuff in this video - costs you no extra but supports this channel if you make a purchase. I appreciate you :)
Agena Astro
• ZWO EAF bit.ly/3UpkRPJ
• ZWO ASIAirPlus bit.ly/4d7oIYS
• William Optics Fluorostar 91 bit.ly/3xRD4fS
Highpoint Scientific
• ZWO EAF bit.ly/3ShwmGu
• ZWO ASIAirPlus bit.ly/3HAsjjI
• William Optics Fluorostar 91 bit.ly/3Pmhhn3
Footage of gears showing backlash from / @wisconline used under Creative Commons (CC)

[@digestthisguy8031]

Excellent explanation, thank you!

[@betafoofoo270]

This is a great example of how these videos should be made. Excellent tutorial, no waffle, silly music or graphics. Just straight to the point with clear informative instruction. Thanks Glenn you have been really helpful.

[@GlennMartinPhotography]

Thanks so much for the feedback, I really appreciate it 🙂

[@subodhshetty1]

Excellent and easy to follow. Thanks much 🙏🏼

[@GlennMartinPhotography]

Thanks for the feedback 😊

[@1clancym]

What a terrific " this is how to do it" video. New subscriber. Much thanks for taking your time to make this video. Really great. Mike

[@GlennMartinPhotography]

Thanks for the sub, I appreciate you!

[@marvinwhisman3333]

Really well done. Great job of both explaining backlash but also showing how to adjust for it.

[@GlennMartinPhotography]

Thanks, Marvin :)

[@boedwards3755]

Well explained. Thanks!

[@GlennMartinPhotography]

Thank you!

[@mikerogers2319]

The backlash you are demonstrating there looks huge. I started experiencing some serious backlash on my ZWO EAF and i tracked it down to slop in the main gear/shaft inside the EAF. Taking it apart and re-assembling is easy ( voids any warranty of course, but this is not a particularly expensive part). I applied a tiny drop of CA glue on the shaft before reinstalling the main gear to get a tight fit. Backlash is almost zero !

[@GlennMartinPhotography]

Great bit of info, Mike! Won't be tearing mine apart any time soon, but certainly if it gets worse I'll be coming back to this comment.

[@iandobbin8068]

Not particularly expensive is relative; to the whole rig, yes, but on a struggling budget, no. Great video and thanks.

[@88cford]

This was an awesome and very easy video to understand. Now I'm gonna go calibrate both my scopes EAF.

[@GlennMartinPhotography]

Great to hear, thanks so much!

[@mikelockwood2104]

excellent video - it's the simple things that make a huge difference

[@GlennMartinPhotography]

Thanks, Mike, glad you liked it 😊

[@gregmac8268]

Perfect! Excellent tutorial and simply explained with a clear presentation... Bravo!

[@GlennMartinPhotography]

Glad you liked it thanks, Greg :)

[@thatastrochap]

Very nice explanation and demo. Definitely going to check my backlash setting and update it. Thank you!

[@GlennMartinPhotography]

Thanks, Chap, glad you found it useful :)

[@stevenmartell9652]

Thanks so much for this, Glenn. I was wondering how I was going to go about fixing the backlash issue, so thanks for making this video and having it just make sense.

[@GlennMartinPhotography]

Thanks for the feedback, really glad it’s helped.

[@MartinLeeney]

Great concise video. Thanks for taking the time to explain it so well.

[@GlennMartinPhotography]

Thanks for the feedback (Martins represent!)

[@coolabahwoodworking]

Great video man. That is really interesting. I didn’t know that happens at all 😮

[@GlennMartinPhotography]

Thanks, Mate 😊

[@BlueTurtleStudios]

That was great Glenn. So well explained I could follow easily. Good Job!

[@GlennMartinPhotography]

Glad you enjoyed it!

[@TheRhike]

Incredible useful and concise video, many thanks!!

[@GlennMartinPhotography]

You're welcome, I'm glad it's useful :)

[@darkrangersinc]

One option you may want to look at for the future for not much more is the Primaluce Sesto Senso it essentially eliminated the backlash in my autofocus routine. Obviously that’s only going to be usable for Nina but if you ever do go that route, I don’t have to do any backlash compensation and my focus curve looks really good and immediately starts changing from the very first step

[@GlennMartinPhotography]

Great advice, Ryan!

[@AntonioPena1]

Very simple and effective presented, many others tried to explained, but you nailed perfectly in few minutes, thanks for sharing your method.

[@GlennMartinPhotography]

Glad it was helpful! Thanks so much for the feedback 😊

[@whatmattersmost6725]

Great video and the best way of setting backlash I have seen! It's VERY important when using Nina or AsiAir Auto Focus!

[@GlennMartinPhotography]

I really appreciate you taking the time to give feedback, thank you :)

[@raymahl]

Thank you so much for this explanation!

[@GlennMartinPhotography]

Glad you liked it :)

[@KevinRudd-w8s]

Excellent tutorial, very useful.

[@GlennMartinPhotography]

I appreciate the feedback ☺️

[@ShayneMostyn]

I looked for this gearing on my phone and couldnt find it ;) Seriously though mate, I think this is one of your best put together videos, well done

[@GlennMartinPhotography]

🤣 thanks so much, mate I really appreciate that!

[@mikehardy8247]

This has been explained by others. Your explanation is completely clear. I'll be doing this on all three of my EAF's soon. I like the ZWO ecosystem, but the lack of easy EAF interchangeability is not kool. I think replacing a split coupler might be possible? THANKS

[@GlennMartinPhotography]

Really glad it helped :) I'd like to think ZWO or your local astro retailer would be able to replace a split coupler, but *maybe* in a pinch using the next size up could get you by in the interim (assuming you didn't throw out the box :-D )

[@mikehardy8247]

I never throw anything out

[@GlennMartinPhotography]

@@mikehardy8247 like a true astrophotographer!

[@vikasch1000]

nailed it - well done!!

[@GlennMartinPhotography]

Thanks, Vikas 😊

[@stlwoodworking]

Well put together video sir.

[@GlennMartinPhotography]

Thank you kindly 😊

[@TheTabugman]

Thanks for the video! Another KZbin channel (can't remember which one) said that the Asiair calculated the EAF backlash automatically...? 🤔

[@GlennMartinPhotography]

That's likely referring to the auto focus routine in the ASIAir App, but before you run that it's handy to have a reasonable focus to start with so the auto focus doesn't go spearing off in the wrong direction and getting lost (don't ask me how I know 😜)

[@TheTabugman]

@@GlennMartinPhotography Thanks! I just googled it and found a ZWO tech guy saying the backlash was only used when focusing manually (and when switching directions) in the app. I'll use your instructions to get any backlash sorted regardless. Can't hurt. 👍

[@PeterRattfeldt]

Thank´s for keeping it short. Great video :)

[@GlennMartinPhotography]

No worries, Peter. I really focused on trying to keep it to the essentails and not go down my typical rabbit hole :D

[@esenb]

That's a great tip. Thanks.

[@GlennMartinPhotography]

No worries 🙂

[@marcovfonseca]

Clever. Tx for sharing!

[@GlennMartinPhotography]

Thanks for watching, Marco 😊

[@seriousbassface]

Completely unrelated lol but was hoping you could maybe help anyways. What are you using to attach the Asiair to the FL91? I have the mounting shoe which goes on the Asiair but have had trouble finding a finder shoe or whatever it is (especially red) that attaches to the FL91 since most I've seen use m4 screws and I believe the fl91 for that spot on the scope needs m6? If i'm not mistaken. Any help is greatly appreciated, thanks a bunch!

[@GlennMartinPhotography]

Yep the holes on the FLT91 take an M6 bolt (1mm pitch). I used the AAP's mounting shoe and just drilled out one of the holes to 6mm (I think it was 6mm, might have been 7mm, use smaller bits and progressivly make the hole bigger until the M6 slides through, instead of overshooting the mark and making too large a hole).

[@seriousbassface]

@@GlennMartinPhotography Ahh nice, looks like that might be what I have to do as well then. Thanks for the reply and advice!

[@Zealor365]

Wow, so easy and accurate too!

[@GlennMartinPhotography]

So glad you found it useful!

[@waldemarwitt764]

Thanks

[@GlennMartinPhotography]

Welcome

[@AZ4Runner]

great video!

[@GlennMartinPhotography]

Thank you 😊

[@sandaruwanmilan9535]

Thanks lot..... can i use this dslr camara

[@GlennMartinPhotography]

Yep with the right T Adaptor you can connect a camera to this scope.

[@sandaruwanmilan9535]

@@GlennMartinPhotography thank you .... can i Asi zwo box connect dslr cam

[@GlennMartinPhotography]

@@sandaruwanmilan9535 check the ZWO website for mobels, but the ASIAir can control different Canon and Nikon cameras, I think they have added Sony too but you would need to check. yourself.

[@sandaruwanmilan9535]

@@GlennMartinPhotography thanks your support ....