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CPC925 Mount saga

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#1 Gary.McK



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Posted 08 April 2020 - 06:43 PM



December 2019 I purchased a new CPC925. Was about 6 weeks before I managed to use it. Noticed a bit of roughness in the AZ axis, but it went away after spinning the mount a few times. Problem was, that the roughness got worse. Spinning the mount would always get rid of it, but initially it would take a few days for the roughness to reappear, but after a bit of use the roughness would return in just a few hours and never really became smooth. I contacted the shop I purchase it from and arranged for a warranty repair. They were very good and even offered to pay for a courier pickup for the scope, however as I did not have the original packaging I offered to drive it to them (about 2 hours driving). Then came coronavirus, and lockdowns, so I was not able to drive it to them, and even if I could, there was no guarantee I would get the scope back quickly as everyone was so uncertain about whether they were going to work or not. Didn't want to be without the scope for an indefinite period.


I had previously owned a CPC1100 that I had replaced the nylon balls with steel ones to fix a similar, but not so bad issue, so I thought I would perform  what I thought would be the fix myself.


Reading about peoples experiences, I found a recommendation for using Delrin/Acetal balls instead of steel. so I ordered these to try out.:




Followed the instructions on Nextstarsite.


Fitted the the balls, reassembled (only took a half hour)  - previous experience helpful, also I spent a couple of years servicing telescopes/optics/binoculars, so not new to this.


****!! Mount just as rough!!! 


Took it apart again, checked the lower track, balls OK, no problems in track? OK, so grabbed the fork and scope tipped it on it's side on a soft surface and had a look at the upper track.  Holy crap, over a quarter of the upper track has a layer of paint in it!!! Looked like overspray/drips from painting parts of the mount. $%&(*( !!


No wonder it was rough!!


How to remove this? Can't scrape as it would possible damage the track... Decided to try dissolving the paint with acetone. After an hour of patiently wiping the track with an acetone soaked  piece of tissue paper, only a tiny amount had come off. Will take days if I continue this. Remembered I had some auto paint thinners, so thought I'd try this. Worked much better, and after a further 2 hours of work the paint was pretty much gone (didn't worry about a bit that was not going to touch the balls.)


Reassembled and tried it out.


Now super smooth, the Delrin/Acetal balls are super, super smooth. Much better than I remember my old CPC1100 with steel balls. The mount just spins and spins, really happy now. Don't know how long the Delrin/Acetal balls will last, but at this stage I much prefer them to the steel balls. Found a chart that showed the balls I bought were significantly stronger than nylon, so I'm hopeful that they will last a while.


Two notes:

My mount had all nylon balls as OEM - not the steel/nylon that was reported several years ago, so perhaps Celestron has gone back to them?

Always check the upper track if you have roughness, bet mine isn't the only mount to have paint drips in the upper track.


Hope this helps some one else



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#2 Tony Bonanno

Tony Bonanno

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Posted 08 April 2020 - 07:47 PM

Wow, what an interesting saga.  I'm waiting for a new CPC 9.25 Edge to arrive.


Wonder about that paint !  Be interesting to find out where that came from and how commonplace it is.


BTW, it was my understanding that only the Edge versions have the steel & nylon balls.. 


Enjoy your scope.  I hope mine gets here before too long..



#3 Michael_Swanson


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Posted 08 April 2020 - 10:49 PM

4 years ago I was told by a contact at Celestron that the standard CPC had been changed to steel and nylon bearings just prior to that.  But, I have gotten conflicting info from Celestron about various production issues in the past so I would say the jury is now out on this...


It is also possible the specific mount you received had been in stock for a while (though 5 years seems unlikely).


Best regards,
Mike Swanson

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