Mechanical Binding Issue with the Celestron SCT Focus Motor

[@HollomanUFOLanding]

I had a similar issue with my CPC1100. Long story short (summarising hours and hours of working on this problem and research online) the only way I was able to get ALL the screws - the 3 on the mounting plate and the 2 hex screws used for motor mounting - snugged up as they should be - and not loose - was to use the orginal focus cover plate with the Focus Motor kit mounting plate installed on top. This is actually a 'fix' that Celestron have been telling people to do along with sending them longer screws to do it. I was lucky in that the screws in my 1100 are long and were able to mount both plates with still at least 1/2 " of threads to spare. Before this fix, the ONLY way I could get the motor to turn was by having the 3 mounting plate screws and the 2 motor mounting screws actually loose.......... It turns out, what's been happening is that the female motor engagemnet shaft has been applying pressure to the bearing via the kit mounting plate. This is what was causing the binding and jamming that people were experiencing. Some people have also installed washers / shims behind the mounting plate to achieve the same relief of pressure on the focus bearing. All my 5 screws are now snugged up as they should be, the motor is working as intended and the motor is not moving on its mount anymore nor seizing up. This product gets filed as another good idea by Celestron but very very poorly researched and tested. It transpires that talking to people who have been involved with Celestron through the decades that this approach is typical of them - bring out a product and let the (suffering ) customers do the R&D. I hope this helps someone down the line.

[@Aero19612]

Thanks for the feedback! Ticks me off to hear that Celestron is sending longer screws and suggestions to fix [their] problem, while the support guy told me he's never heard of those screws getting loose. I totally agree that Celestron is using its customers as its beta testers. I must say, I don't understand how the focuser works for a "long" time when the screws get loose. Mine just get more loose as I continue to operate it until, if I let it go long enough, the focuser would come loose from the bracket. I also don't understand how placing the original cover plate between the OTA and the new bracket helps.

[@reidkonschuh2246]

Thanks for posting this. My focus motor was working fine until I removed it and put on a ZWO EAF for some astrophotography, but when I put the Celestron focus motor back on it would constantly stall. I tried the three washer trick, and Loctite on the screws and it worked. Also, I think part of the problem is before you tighten down the two screws that hold the motor to the plate, tighten the screws that hold the motor to the shaft. Otherwise, the motor may be a little off kilter on the shaft if you snug down the screws that hold the motor to the plate too much.

[@patchyadventures]

Hi James. I just went through the same problem last night with my Celestron Focus motor: the three set screws for the adapter plate loosened from the OTA which caused issues with my N.I.N.A autofocus routines. BTW I added a tiny amount of blue Loktite on the screw threads, which will hopefully stop this from happening in the future. Watching your video helped me to troubleshoot the issue. Thanks for taking the time to present your findings and solutions!

[@Aero19612]

Glad it helped, Anuraag! I'm just now getting the C9.25 on the mount again and have my fingers crossed that the focuser stays on...

[@DaveAndrus]

I just bought a Celestron focuser and installed it today on my C8se. Bummer--nothing moved! Going back over each step, I realized that the new adapter plate was the culprit. I carefully looked at the standard plate and this new one. There was an obvious difference--the standard plate had a 20 thousandths recess carved in it where it contacts the face of the SCT's focuser bearing, and the new adapter had none--it was smooth on the underside. Installing this new adapter plate caused a significant amount of binding on the focuser shaft. It was easy to feel the difference just turning it with my fingers, even before installing the motor. The underside of the new plate is .020" closer and is putting pressure on the face of the SCT's focuser bearing. The amount of torque needed was so much that the motor would frequently stall. That's really annoying, to say the least! I could make the motor work fine, but only if I left the 3 screws on the new adapter plate very loose, and then the motor and the whole assembly had way too much play in it. My solution was to add 3 thin washers between the new plate and the SCT body, one for each screw. Luckily the standard screws had enough threads to do this. I tried using the standard plate under the new one as someone suggested, but my screws only had about three threads showing, and I didn't dare put that much torque on them. It's really annoying how "fiddly" this product is. Thanks for your video--it gave me the idea for the washers, and most importantly made me feel that my problem was not user error!

[@Aero19612]

Hi Dave. Glad you were able to sort it out. The Celestron focuser is a very frustrating piece of astrogear, to be sure. It seems clear there was no extensive design-build-test-refine cycle in the process. Just throw it out on the market and let the buyers crowd-source homemade solutions. Thanks for watching!

[@mikaellindkvist1844]

Very helpful to watch this video and read some of the comments. I installed the focuser on my 9.25 a few weeks ago and have had problems from the beginning. At first I was convinced it had something to do with the software (Im using the USB interface since I have a EQR-6 PRO mount). The focuser would sometimes work for a while and then just stop working which made it really unpredictable. After seeing this video I reassembled it from the beginning and looked at it more carefully. As has been mentioned the design is really bad, in my case the mounting plate has not moved but I realised that when you tighten 2 hex screws to attach the motor it actually presses directly against the bearing which can make it stall (depending on the pressure). I loosen the 2 hex screws a bit and now it seems to be working (have not had the time to test it properly yet) but the focus motor itself is wobbling a bit. I will probably have to do a better fix in the long run, e.g. adding some washers and longer hex screws and maybe even trying to make some custom adjustments to make it possible to use 3 hex screws instead of 2.

[@Aero19612]

Hi Mikael. Yes, I think it is a poor design. There are two “flaws”, I believe. The design does not include an effective flex connection between the motor and the SCT focuser shaft, so Celestron recommend as not tightening the screws to permit the motor to wobble as a means of aligning its motor axis with the SCT shaft. The second issue is that they are relying on very small screws in the OTA to connect the focuser to the OTA body. This last issue is particularly bad for me because one of those threaded holes has damaged lead-in threads so the wobbling works that screw loose. I have since bought longer screws and installed them with LocTite. I haven’t had a chance to test it thoroughly, but it hasn’t come loose since. My fingers are crossed, but my confidence is not high. Thanks for watching!

[@kevinburke8608]

Why is it that every time I have an issue, I find you have come up with a solution for the issue... (well I do have many of the same items you have, lol) I hope Celestron watches your videos.

[@Aero19612]

Ha. Well, for what it’s worth, the longer screws + LocTite have solved the problem so far. Got through all of galaxy season without a “loose” focuser. So, just maybe, this solution actually is working. Fingers crossed as always. Thanks for watching, Kevin!

[@nevillefraser8827]

Thanks James for this. Exactly my problem and exactly the fix for it! Great work!

[@Aero19612]

Excellent, Neville! I haven't had the focuser come loose since I replaced the short screws with longer screws and installed them with Loctite. Fingers still crossed though...

[@louisrosner7902]

Another informative video. I have the same focuser on my edge 8 HD. I’m going to take it off and look to see if I have the same problem and I’ll let you know. I think blue Loctite is certainly in order. So far I’ve had no issues. You brought up another good point that this focuser certainly needs backlash compensation. I wasn’t using it and it’s always a bit of a bear to get a good focus back-and-forth.

[@Aero19612]

Thanks for watching, Louis! I hope my issue is "rare", but, by all means, let me know what you find out. I think almost any focuser will require backlash compensation, especially when used with V-type or hyperbolic curve auto-focus algorithms that pass through optimum focus and have to back track to the optimum. Thanks for the blue Loctite recommendation.

[@MrBebopbob]

Hi James, You answer my question at 9:30ish. Thanks again for your great videos.

[@Invisible_one]

Hi James, I had an issue with binding once with the Celestron motorized focuser as well. It was totally unrelated to your issue it sounds like. The three screws that are in a triangle pattern around the focus shaft are not used to attach the motor to the scope. However, if you accidentally tighten any of them at all the motorized focuser will bind badly. It's easy to tighten one by mistake because the are right above the two screws that DO attach the motor to the OTA. Hopefully that helps someone.

[@Aero19612]

Great feedback, Charles. Someone else noted that over-tightening the three screws affects the rotational stiffness of the SCT focuser shaft. All of the comments to this video serve to highlight weakness in the "system" performance. The electronic focuser works fine. The SCT focuser works fine. The interface that connects the two subsystems is the weak link.

[@Invisible_one]

@@Aero19612 I meant the 3 screws on the motorized focuser itself. Not the ones that are on or connect to the OTA.

[@briandenley]

Charles Thompson ...there are only two if you mean the captive screws. I just installed my new focuser and I don’t like the way it sounds.

[@Invisible_one]

@@briandenley it is louder than the other focus motors I have used but I haven't had any issues with it's performance. I'm using it on a RASA 8 and RASA 11. I attach the mounting plate and get those 3 screws as tight as possible without binding. Then slide on the focus motor and tighten the 2 mounting screws. Finally, I tighten the set screw and the clamping screw. So far it hasn't worked loose on either scope.

[@briandenley]

Charles Thompson thanks

[@DJRonnieG]

I had a weird experience with my PrimaLuce Lab Esatto focuser last week. I ended up resetting it's power supply then re-running the calibration. I also use the PrimaLuce lab "SestoSenso II" focuser (directly attaches to the 10:1 nob on my feather touch focuser) for when I'm doing planetary imaging. I still have yet to setup auto-focus in general. It would be nice as temperature changes affect the focus. The dead of winter was fine because once it's 10 degrees outside, it doesn't seem to make much a of a difference if it gets any colder. Good luck with resolving your issue. Wish I had idea other than "re-run calibration and check your torque", but clearly you seem to be a little ahead of me in the focusing department.

[@Aero19612]

Thanks Ronnie! Yea, the power supply and calibration aren't my problem...this time. How do you "reset the power supply"? Unplug it and plug it in again? I'm jealous of people why set their system up and leave it running unattended all night as it performs occasional auto-focus runs and you wake up to a boat load of data.

[@DJRonnieG]

​@@Aero19612 I basically power-cycled the focuser.. On the first of two nights this was not successful, so I tossed my hands up and plugged the focuser into it's own power supply. On the second night I went back to attaching it to my Pegasus Pocket Power Box and had more success. This time when I encountered trouble, I power-cycled all of the AP gear, instead of just the focuser. Most notably, I re-seated the power power connector which feeds the Pegasus Power Box power from the 10a power supply. Maybe I had a loose connection? Still not sure but unlike the first night, the problem did not persist after taking this fairly minor corrective action. I also envy those who are able to gather a boatload of quality data from an unattended evening. Without auto-focus, I've only avoided blurry frames on nights where the sessions begin and end with temperatures that are below the freezing point. As it stands now, I just stay up and keep the remote computer's display on one of my screens. Meanwhile, I perform another task or I play a video game. If I'm exhausted and can't stay up, I just set my alarm and sleep in my chair during imaging runs. Sometimes the alarm is just an insurance policy against wasting an hour or more of clear skies. We've still made significant progress if we can manually control the operation from within our cozy homes. However, it would indeed be one heck of an improvement if we could sleep through the whole night while our devices and instruments handle the image acquisition.

[@joecooksey4331]

Re-tap the threads. I installed this on my 6 inch yesterday. Works fine, but the instructions show the mounting plate to be installed with the notched side to outside of the OTA. I installed it just the opposite because I wanted to mount the focuser vertical so it doesn't interfere with mu DSLR and the holes were slightly off so I couldn't get both screws started. The other thing I noticed is even though I tighten the set screws before I ran calibration it seemed to run too long and sure enough with it running and a flashlight the brass tube was not moving. I tightened some more and it was fine. The insert that slides over the brass needs more than just plastic. It needs a liner to grip better.

[@Aero19612]

Hey Joe. I suppose I could run a tap through the holes. Might be worth doing. Did you put Loctite on the three screws? I agree, the plastic "clamp" is not terribly reliable. The same thing happened to me when I first installed the motor and ran the calibration. It just ran and ran because it wasn't mechanically coupled to the brass knob. Let me know how things work out under actual usage. Thanks for watching!

[@joecooksey4331]

@@Aero19612 No... no Loctite. I don't like that idea with something that size if I ever want to get it off again. If you re-tap it only start it by hand and when you think it's started use a 1/4" small wrench to turn it. Worse case... drill it out for next bigger size and tap it. I did notice yesterday I probably striped the allen head on the clamping screw. If I want to get it off again I'll epoxy the wrench in place and take it out. I'll need a new screw but that won't be a problem. With it off I'll make some kind of thin rubber sleeve for the brass like heat shrink.

[@joecooksey4331]

@@Aero19612 If you tap it all taps are not the same. You'll want a taper tap which are the most common.

[@Aero19612]

I don't have easy access to machining equipment so I'm trying to solve all of my problems with string and duct tape. Good advice on the tap. Thanks. I did use removable-grade Loctite on the one screw that keeps backing out. I also ordered additional screws that are 2 mm longer. Once it binds up again, I'll try to run a tap, install the longer screws, and probably Loctite them for added security.

[@marcus576]

I know this a bit old, but I was wondering if you resolved this issue? I thought the notch in the base plate was supposed to align with the notch in the focuser body, and ideally, those notches were supposed to align with the visual back. I wondered if having the base plate and focuser body notches unaligned may have created a space that wasn’t flush? I was about to buy this for my c-11, but I am going to hold off now until I learn more about potential issues.

[@Aero19612]

Hi Marcus. The notch can go anywhere. The main issue with my setup is that the first few threads in one of the three holes on the OTA side are bad, which means that the short screw can't get a good hold and works loose. I have since replaced the original short screws with longer screws and put LocTite on the threads. It has not come loose since, but I also haven't had the chance to use it a lot. My fingers are crossed! Thanks for watching!

[@jerrysamuelson1247]

I had just bought one of these last week. This motor had a binding issue also. Had one heck of a time getting to the set screw and the clamp. The wrench would not turn the motor. Froze up. I sent it back for a refund. Looking for something better. Pegasus Astro Motorized Focuser may be something to look at. Nice video.

[@Aero19612]

Hey Jerry. My focuser on my refractor is the Pegasus Astro FocusCube2--it's great. I was so impressed with it that started to purchase their focuser for my SCT. It sat in my "basket" for several weeks and then I happened to see that Celestron had just released their focuser so I bought it instead ($100 less). I thought the direct connection would be better than the belt drive. I'm sure the Pegasus Astro SCT focuser will be fine. It may use the same three screws for attachment, but maybe they are accessible without having to remove the focuser. Thanks for watching and good luck!

[@jerrysamuelson1247]

@@Aero19612 I thought that the direct drive would work great also until the motor locked up and I couldn't even turn it with that supplied wrench. I did get a little nervous on how I was going to remove it because the set screw and the clamp screw were of course covered. But I managed. I'm real new at astrophotography so I'm now setting up the SCT to be controlled by my laptop. You almost have to have a motor driven focuser if you're going to do that or it will be a lot of back and forth stuff. On your refractor, do your have to purchase the Pegasus controller since I would be focusing the Pegasus Astro Motorized Focuser from the laptop? Thanks again for the knowledge based videos. Big help.

[@Aero19612]

The Pegasus Astro Focuscube2 is a stand-alone unit. Just plug in the 12v power supply and the USB2 cable and you’re good to go.

[@jerrysamuelson1247]

@@Aero19612 Hello, I just received my Pegasus Astro Motorized Focuser & Controlller. Wish I would've bought the focus cube 2 instead but the other one was already shipped and this will work out. Going to install it today on my SCT. Clear Skies!!!

[@jerrysamuelson1247]

@@Aero19612 OPT accidentally sent me the wrong combo of the Pegasus Astro Motorized Focuser & Controlller which when they were wired per instructions it smoked them from what the Pegasus rep. told me. So with his and OPT's help, I sent back the defective units. I'm going to purchase the stand alone unit, Focuscube2 but I wanted to let you know that there is an optional hand controller for the FocusCube2 that I think I'll get for when I'm just viewing through an eyepiece. This is it: pegasusastro.com/products/hand-controller-for-focuscube/ Thought you'd like to know if you didn't already.

[@patwicker1358]

As expensive as those focusers are, it is pretty cheap of them to not include new screws. Also that probably plays heck with you backlash compensation.

[@krellon]

Pat Wicker Thing that surprises me more is the fact Celestron rotated and re-drilled a 2 cent fixing on a 2-3k+ scope!

[@Aero19612]

Yeah, I'm a bit disappointed. The focuser itself is a fine bit of hardware and works well, but that interface could have stood a bit more thought. Thanks for watching, guys!

[@RobB_VK6ES]

@@krellon What is the difference between Skywatcher and Celestron ? Celestron is the pig with lipstick :)

[@louisrosner7902]

Son of a gun. Spent the whole day trying to fix this darn Celestron focuser. It was certainly loose just like you showed. Took everything apart. Used a micrometer to make sure when I tightened down the plate that the central brass bushing remained true in the center. Loctited all the bolts put everything back together and everything seems to be working beautifully without that wobble that was loosening up all the screws. Thanks again Even though I spent the whole day on this but it was worth it. Again if you have any recommendations for APT settings for this focuser you can pass them along.

[@Aero19612]

Great news, Louis! Keep me posted on the Loctite solution. I will be going that route as well. Were all three of the threaded holes in good shape? For my focuser/OTA combo, I found that no filter offset adjustments are required (but I have parafocal filters produced by the same manufacturer) because the 1 step is "fairly large." I use a backlash compensation of 20 steps. I describe how I got these numbers in an earlier video: "First Use of the Celestron Focuser on my SCT".

[@MrBebopbob]

Hi James. I don't know whether you check comments on your older videos, but.. I have a question about this SCT focuser I was hoping you would have the answer to. I too have a 9.25SCT and the same focuser. I noticed the other night that the focus was acting goofy (swings in focus position of 35 to 40) so I inspected it and found the plate had loosened (as you have had problems with). I disassembled the focuser, replaced the m3x8mm with m3x12mm screws and put a small amount of blue loctite on the trheads. When I had the thing reassembled, I noticed that I could turn the shaft (the part you point to at 1:00 mark of your video) back and forth (say 1/32 - 1/16 turn) which I don't remembering if it did this before. Does yours do this? Is this the origin of the focuser backlash? I must say this is a mickey mouse design for the adapter plate. It is a pain in the neck to align (both concentrically and for level). I ended up 3d printing a bushing to align it concentrically but the level alignment is just a poor design. Thanks in advance if you can answer this question, and if not thanks for the very well done videos. Your methodical style is very informative for an old retired engineer. Bob

[@Aero19612]

Thanks Bob! Us "old" engineers gotta have something to do to keep us out of trouble. I saw your later response that about the backlash. So far, after using longer screws and Loctite, the plate has stayed on. Still not willing to claim victory. If I can get through the next Galaxy Season without it working itself loose, maybe.

[@michaell1473]

I tried for weeks to get my celestron focuser working, turns out it was a bad torque sensor. I found that my focuser works better if I leave the focuser mounting screws a bit loose and keep the mounting plate tight. It will wobble a bit but wont bind as much vs. the focus knob spindle. It does ad a bit of backlash though.

[@Aero19612]

Interesting, Michael. I can see how allowing the focuser shift can allow it to "find" the proper SCT focuser shaft axis. Good luck!

[@bernarddube5626]

Hi James, newbie questions here Do I have to have a camera connected and does it have to be looking at the sky to work? It's on USB alone not looking up, should it work this way? How do you get it to calibrate? It is not working off the shaft and the light is on.

[@Aero19612]

Hey Bernard, No. You do not have to have a camera installed for the focuser to operate. USB power should work, however, you must calibrate it first before you can have it move. Celestron has a driver and stand alone focuser control software that you can use to calibrate the focuser. Check the Celestron site for this software. Good luck!

[@bernarddube5626]

Hey James, I finally found this driver, installed it and everything is working now. Thanks for helping and thanks for all those great and helpful videos. Clear skies. Bernard.

[@davidf9494]

Great Diagnostic video James and while I haven't had any problems with my EDGE HD8 and focuser (touch wood!), it's good to know your video exists in case this ever happens. I'm not using a backlash setting right now and am getting typically 1.2-1.4 HFR with my setup. Do you have any quick tips for calculating the focuser backlash? Thanks again for your informative videos!

[@Aero19612]

Thanks for watching, David. I'm glad you're having such great success with your setup. As for backlash, you can see what I did at 18:00 min into my video "First Use of the Celestron Focuser on my SCT". Good luck!

[@davidf9494]

@@Aero19612 Thanks James - I missed that video. It's well detailed!

[@JohnMcGFrance]

David Fielder Keep an eye on it David. I have the Edge 8 and mine came loose like James and a few others I know.

[@JohnMcGFrance]

Hi James. We seem to going through the same issues with the same gear! I have the Celestron motor focuser and it has loosened in the same way, although it didn’t bind so lucky there. Did you manage to find any suitable replacement screws? Also, when you guys discuss loctite I’m unsure what you mean. Is this a particular thing for screws, as here in France it’s just a brand name with a host of different products. Don’t want to apply the wrong stuff and make a mess of things. Appreciate your time in making these videos. Really helpful.

[@Aero19612]

Hey John. I measured the screws. They appear to be M3x0.75 x 8 mm long. I ordered some that are 10 mm long but have not removed the focuser yet to see if they will bottom out on something. I suppose they could be files down if necessary but they are really small and difficult to get a grip on. I'll comment back when I've tried them out. Yes, Loctite makes a lot of stuff. There is the "red" Loctite for permanent installation and "blue" Loctite for removable. This is what I bought: Loctite Threadlocker Adhesive, 242, Removable Grade

[@Aero19612]

Typo. The Celestron screws are M3x0.50 x 8 mm. Probably could find a 0.75 mm pitch screw if you tried.

[@JohnMcGFrance]

James Lamb Thanks James. The blue Loctite is on order. I’ll try that first and keep an eye on things. If it comes loose again I’ll look into the screws you mention. Any thanks.

[@gauthierdaniel828]

I think with some loctite it will help and the big backlash is not a problem for me because i have 2 clutch on the primary mirror on the 11" edge hd

[@Aero19612]

Right. I've since replaced the shorter screws with longer ones and used Loctite. I haven't had it come loose since, but I need to use it a while longer before I claim victory. Thanks for watching, Gauthier

[@johnshu5331]

Aloha Jim, I really like all your videos and a great resource for information. I bought the digital angle guage, and set up Stellarium the way you have it. I'm still try to decide what kind of electrical focuser to get for my C11 Edge. Was just curious if you're still using the Celestron Focuser? Also if you have time, can you do a review on that Pegasus FocusCube Zero (for SCTs)? That seems like another good option. Thanks!! John

[@Aero19612]

Hi John, I still use the Celestron focuser. I have 2 Pegasus Astro FocusCube2's for my refractory but not a FocusCube0 with an SCT attachment. I really like the Pegasus Astro equipment. The thing I question with their SCT focuser is the belt drive. Probably works just fine. You might also consider the ZWO focuser with the SCT mounting hardware. It has a direct mechanical connection. Both of these focusers leave clear access to the 3 mounting screws on the back of the SCT so you can tighten then each night. The Celestron motor covers the screws and you only know the screws are loose when the focuser binds up. Given a choice, I might give the ZWO a shot. Hope that helps!

[@johnshu5331]

@@Aero19612 ok thanks that is good to know! I saw the belt drive and they advertise zero backlash (but didn't find any reviews on it). Will have to look again and check out the ZWO focuser. I have one of those Starlight Instruments feather touch focusers on there now (just doing manual focus with it for now). Thanks again!!

[@MGR1900]

Does anyone know what was improved on the 2nd version of this product specifically? I have an Celestron CGX1100 with the first version and was wondering if the second version would be worth it.

[@Aero19612]

I don't know the answer to that. You might send Celestron that question through their support portal.

[@MGR1900]

@@Aero19612 Thank you. I think the 9.25 HD CGX didn’t fit with version 1. I am going to call them.

[@rudiroothooft2414]

Thanks, Very helpfull

[@Aero19612]

Hi Rudi. I haven’t any problems since I replaced the Celestron screws with longer screws and used LocTite on the threads. Still keeping my fingers crossed though. Thanks for watching.

[@wanderingquestions7501]

My 20 year old C8 focus binds up too; the problem is at the same spot. Don’t know why Celestron can’t make this simple mechanism work well. It’s really a shame to see that after decades Celestron hasn’t done a better job.

[@Aero19612]

First, I didn't realize the C8 had been produced for 20 years. Are you saying the manual focuser binds? Or it's this electronic Celestron focuser that's binding? Either way, it highlights a design flaw.

[@wanderingquestions7501]

James Lamb My scope was specifically called the ‘Celestar 8’. It had the old wedgepod mount. The electric focuser I got way back is just like the JMI Motofocus available today. If one look at that it has the same replacement adjuster stem plate and screws methodology to mount a small nurled knob on the C8 focus. The problem was the replacement plate did not keep the focus rod that goes into the OTA truly centered and the off-center focus rod would bind. It didn’t matter if the electric focuser was in place. Just turning the focus knob manually, one could feel the binding. It was always a temperamental setup. I’m not saying it’s the same problem you’re having. The solution, on my unit, is to have to exact screws needed to help that base plate truly square-up in position. In sum, I could feel the focuser’s binding when operated manually and the electric focus would slow as rotated through the binding positions. One was aware of binding in both applications. In my thinking it’s all about how that after-market place seats and that’s what i fuss with.

[@Aero19612]

Well, it's a different setup but it certainly sounds like a very similar root cause for the problem.

[@emilcarste]

I installed this a couple of days ago on my RASA 8". I can see that during calibration, when motor is running and move the focus from one end to the other the motor body also sligthly moves. Is this normal?

[@Aero19612]

Emil, Yes, I think that is normal. Celestron says not to overtighten the two captive screws that attach the motor to the bracket or to overtighten the clamping ring to the OTA focus knob. So if you don't overtighten them, you'll probably get some wobble out of the motor. Keep an eye out for loosening of the three screws that attach the bracket to the OTA. Good luck!

[@denodan]

I tightened my plate down till it was harder to turn the focus shaft, then back off and that worked

[@denodan]

@@Aero19612 don't tighten the clamping screws to shaft tight enough then motor will slip on focus shaft. Its been an issue with this happening. The grub screw, with lock tight can be deserving as the lock tight grips and easy to assume its tight when in fact its just tough to screw down any more. My motor does not move

[@Aero19612]

@@denodan Yep. This is a very temperamental design. Not sure Celestron thought through the design.

[@denodan]

@@Aero19612 I tightened everything down except the plate, so far no motor movement or coming loose. They way I tightened my plate was do it up till the ficuser was getting hard to turn, than backed them off, and so far perfect. The grub screw is deciving as you may think its tight but not, so crank it down

[@compubyte2010]

Same problem, kept binding up.. and the bottom plate moves a tiny bit. Like yours

[@Aero19612]

Hey Frank. Sounds familiar I replaced the original (3) 8mm long M3x0.5 flathead screws with 10 mm long screws and used Loctite Threadlocker (Blue) 242 to provide extra resistance. The focuser hasn't come loose since, but I'm not going to claim victory for a while yet. Confirm the size of the screws in your OTA if you go down this path. Good luck!

[@compubyte2010]

@@Aero19612 i just finished pulling mine apart 1 of 3 screws was OUT just hanging there, touched it and it fell into my hand. All 3 were loose . Tightened everything . If it happens again locktight or larger screws ..

[@Aero19612]

Again. Sounds familiar. I would recommend Loctite AND longer screws. Let me know how things turn out.

[@compubyte2010]

@@Aero19612 absolutely, like I said, tightened it up, if it comes loose again ( when i should say) lol . Don't have any, locktight , gonna buy some this week. Think i have longer screws at home! My fix as temporary.

[@denodan]

I notice in the video you have the plate the wrong way round, the cutout part meant to be on the inside facing your visual back

[@Aero19612]

Hey Dennis. Actually, the orientation of the cut-out doesn't matter for my SCT. I suspect they put it in for when that bracket is used with a smaller SCT where there is possibility that the bracket will interfere with the visual back when the focuser is closer to the visual back.

[@denodan]

@@Aero19612 as far as i know the instructions and everyone else say that cutout must face the visual back. The 5 and 6 " the cutout goes toward the outside, for larger the cutout goes towards the visualback

[@denodan]

@@Aero19612 no instructions say on 5 and 6 I inch that cutout goes toward the outside, 8 and above the cut out goes toward the visual back. The installation instructions are clear on this, maybe try it the proper way and see what happens? There is a possibility they are clear which way it goes as it may be seated better, worth a try?

[@Aero19612]

That's interesting. I may try to get clarification from Celestron on that. Makes no sense to me. That said, I'm certain the reason my focuser works itself loose is because the damaged threads in one of the threaded holes on the OTA side combined with having to re-use the very short screws. I have installed longer screws with Loctite and it has not loosened since. Thanks for the heads up, Dennis, I'll look into it further.

[@Aero19612]

Just dug up the instructions. It appears that the 3-hole pattern in the OTA is oriented differently in the 6" and 7" from the 8" and 9.25". The cut-out is opposite one hole and "bisects" the other two holes. Note that instruction step 14 says that the cover plate can be rotated if you want. So the orientation of the cut-out is not important (other than the 3 holes have to line up with the 3 threaded holes in the OTA, of course).

[@denodan]

My main concern is, if the motor binds in a postion you cannot access the locking shaft screws, your basicallt stuffed and no way to unclamp the shaft locking screws. Your lucky you could access them. Else would have been stuck

[@Aero19612]

Yes. I had that concern as well. However, If that does happen, I'm thinking that I could disconnect the focuser from the bracket via the two screws and then use the focuser itself to turn the know to an accessible position. Still, I'm crossing my fingers that scenario does not happen. Thanks for watching, Dennis!

[@denodan]

@@Aero19612 I emailed celestron about that issue as its a flawed design

[@Aero19612]

Don’t hold your breath waiting for a response. When I raised the issue with them, the support team told me they’ve never heard of the screws loosening.

[@JamiesonTeo]

Would using some loctite help?

[@Aero19612]

Hey, Deacon Yes, I think Loctite is the simplest approach so I'll definitely be trying that out. I just wish the mechanical connection wasn't so flimsy. Thanks for watching!

[@RobB_VK6ES]

Helicoils and longer screws are the solution to this issue I suggest. Be sure to use a medium strength screw rated Locktite type adhesive to the Helicoil to scope body interface. If the back cover of the OTA is too thin for Helicoils then perhaps tap oversize M5 and drill & counterbore the adaptor plate to suit. I am considering a similar Helicoil mod to the CGX saddle clamp threads. The standard steel into aluminium tends to lock up causing me to worry about long term viability of the aluminium threads in the saddle. With the steel insert friction will be much lower and harder wearing. FYI I am using a standard geared stepper directly connected the UPB Pro on both of my scopes. www.omc-stepperonline.com/geared-stepper-motor/nema-17-stepper-motor-bipolar-l33mm-w-gear-raio-271-planetary-gearbox-17hs13-0404s-pg27.html

[@Aero19612]

Hey, Rob I can certainly understand why they didn't install helicoils in the first place--all they wanted to do was attach an unloaded cosmetic cover plate to the OTA. Now, however, a thicker plate, longer screws, and helicoils are called for. Oops. Hurts to miss that one. I have no hope of installing helicoils--you're the expert machinist, remember? At this stage, I'll try and find longer screws and apply some Loctite. Oh, and see if Celestron wants to weigh in with suggestions. Your saddle clamp application should have had helicoils in the first place--it's holding heavy, expensive equipment. Geez. Do you have one of those stepper motors attached to an SCT? If so, how did you mount it to the back plate? Thanks for watching, as always!

[@RobB_VK6ES]

@@Aero19612 Yeah I probably jumped the gun with the Helicoil advise. At M4 there is not much room for error and would be a bit fiddly. Longer screws may do the job OK assuming there is good thread at the bottom. If C short tapped the hole increasing the thread length with a bottoming tap would be a very good idea. In either case I would start with a screw longer than needed and cut/file to a perfect length to maximise engagement. I would NOT recommend trying to deepen the existing threaded holes as there lies disaster. I don't have an SCT, both the WO ZS126 and the carbon RC8 have Crayfords so installation was the same for both and I can share the UPBv2 Pro between both scopes on a seasonal basis. Others have used this motor with SCT's have a look at Robert Brown's My Focuser Pro documentation on Sourceforge or even a simple google search. While on the subject of sharing the UPB around I need to make another dovetail mounting for the RC8. If you want, I would be pleased make up something for you as well. Just yes or no and I will contact you via your youtube details. Just my way of saying thanks for the great content. I am also in the process of fine tuning the CGX and may make a video on the process as I see so much misinformation such as using ceramic bearings and replacing the main bearings when "Hypertuning" mounts. Based on my sample of two Synta mounts I have an opinion on the source of "stiction" on these mounts and it has nothing to do with bearings but rather fit of the clutch drums into the housing.

[@Aero19612]

Hey Rob. If you're not careful, one day I'm going to take you up on having adapter plates made! Truly a very nice offer. The "M4" screws I thought were there are actually M3x0.75 x 8 mm long screws. I re-installed the offending screw with Loctite. In the mean time, I ordered 10 mm long versions of the same screw. Should be here tomorrow or Monday. Of course, you just can't order 3 screws, so I'll have 97 left over. I'm sure I can find a use for them around the house. NOT! Not sure if the extra 2 mm is too much. May have to file them down as you mention. Nothing is easy. Indeed, you should make a video of your CGX adjustments. Too much misinformation out there. This is a highly technical hobby and needs knowledgeable people creating content to counter the poorly thought-out material out there. Stay safe and clear skies!

[@Aero19612]

Typo: The Celestron screws are M3x0.50 x 8 mm (not 0.75 mm pitch) for anyone interested in replacing them

[@sodakastronut]

Known issue - www.cloudynights.com/topic/645522-celestron-electronic-focus-motor-for-sct-and-edgehd/

[@Aero19612]

Thanks for the link--I'll read through it to see if there are better solutions than the ones bouncing around in my head.

[@aakoksal]

Removing the imaging train would make your life less painfull...

[@Aero19612]

Haha. Apparently I’m not comfortable unless my life is painful. Actually, since I added longer screws and LocTite, the focuser issues have been dealt with, so everything’s running OK…for now. Thanks for watching!

[@bernarddube5626]

And I'm using an EQR-6 PRO.

[@linho7667]

Don’t buy this. This product is full of flaws and easily damaged. My motor was died at the first day, a plastic gear broken

[@Aero19612]

It can work, but many of us have had to fiddle with it a lot more than we should.

[@linho7667]

⁠@@Aero19612I have disassemblied the focuser and disappointed. They use a lot of plastic gears in the main motor, it is easily damaged. It looks like a toy rather than a real equipment.