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lamplight
Carpal Tunnel
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Reged: 09/18/12

Loc: western MA, U.S.
AZ not so smooth on CPC 800 (pushing manually) new
      #5749911 - 03/22/13 03:01 PM

Hi
I use my CPC unpowered quite a bit.. (I know they make other scopes and mounts for that but just bear with me

With the clutch disengaged fully there are a few rough spots in the azimuth left/right rotation. Ie: its just a little sticky.. In some spots requires a bit more force than others.. hope I explain clearly...

It's less than a yr old .. Pretty much been like that since the beginning but wasn't really a problem until recently doing some long focal length starhopping right in the spot.. Was driving me nuts...

Any recommendation on what I might be able to accomplish myself to make it better? I'm a bit hesitant to take it apart without any guidance. There's no issue when its powered that I've noticed.. The gears seem to compensate fine.. Well, thought I'd ask. Thanks


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MikeBOKC
Post Laureate
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Reged: 05/10/10

Loc: Oklahoma City, OK
Re: AZ not so smooth on CPC 800 (pushing manually) new [Re: lamplight]
      #5750434 - 03/22/13 07:22 PM

Well I'm going to suggest (no offense intended) that the CPC mount is just not designed to be used that way, and that doing so might cause some wear or damage internally that would otherwise be avoided. The whole design package seems to be optimized for go to and automated use, and not for manual. Unless I am moving the scope around prior to alignment to get settled on my first alignment star, I always leave the CPC with clutches fully engaged and driven by the hand controller. Doint otherwise seems sort of like trying to manually shift an automatic transmission car.

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Escher
Pooh-Bah
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Reged: 08/30/07

Loc: Fenton, MI
Re: AZ not so smooth on CPC 800 (pushing manually) new [Re: MikeBOKC]
      #5750782 - 03/22/13 10:10 PM

Please refer to the "bearing mod" that has been covered several times regarding the harshness in movement. Here is a link to my complete overhaul and bearing mod on my CPC1100:

CPC1100 Overhaul and Bearing Mod

Bear with me - I'm going into full Engineer mode...

The design of the system and use of both a tapered roller bearing on the main shaft and thrust bearings around the circumference does a very good job in supporting the weight of the telescope, but the factory nylon bearings develop flat spots over time. Swapping them with proper chrome ball bearings and a high quality grease will drastically improve the smoothness of the movement and the tracking ability. My tracking during imaging went from approx 10 seconds to nearly 1 minute with round stars.

As to spinning the mount while unlocked, it may cause some premature wear on the standard nylon bearings, but that is only if you literally spun it round and round and round enough to wear a channel in the bearings themselves... Once replaced with the chrome versions, I could see the bearings eventually burnishing the aluminum casing, which would actually be beneficial, but would possibly require shimming to account for any material removal during the process.. Once again - this is assuming you spun the scope as if it were an axle at a few hundred rpm for a period of time... under normal slewing and / or manual slewing it will take years for this to occur.

The design of the clutch mechanism is quite good actually, and much better than similar Meade offerings... a rubber friction plate is used and a teflon washer is used for spacing. The rubber friction surface gives a very nice positive lock without slippage...

I don't see anything in this clutch / drive system that could be damaged by manually spinning the scope... the teflon washer allows a nice free movement when the clutch is not engaged. There is no mechanical interlock between the drive gear and friction plate... only the static friction between the drive gear and the friction plate is used to engage the drive... if there is no pressure to engage the clutch, there is no way for the system to interlock.

The only thing I would look out for if you want to manually slew with the drives unlocked, would be that you *fully* unlock each clutch... if you partially engage, you could wear the friction plate rubber surface via the drag of the drive gear along its surface....

Edited by Escher (03/22/13 10:12 PM)


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N7XW
sage


Reged: 05/04/07

Loc: Westport, WA
Re: AZ not so smooth on CPC 800 (pushing manually) new [Re: Escher]
      #5751009 - 03/23/13 12:17 AM

I don't mean to hijack the thread, but I have a few questions -

Is it beneficial to do the bearing upgrade to the 8" CPC or is it not necessary due to less load?

Do all three sizes (8, 9.25, 11)use the same size gears?

Does the HD use the same nylon bearings as the standard CPC?

Thanks.


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: AZ not so smooth on CPC 800 (pushing manually) new [Re: N7XW]
      #5751214 - 03/23/13 05:22 AM

The upgrade only seems to be needed if you are mounted equatorially, in alt az mode the load is taken by all the bearings.

I think they are all the same size.

The later CPC scopes use alternate steel and nylon bearings. The Celestron technical people tried all the options and found this to be best.

Chris


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N7XW
sage


Reged: 05/04/07

Loc: Westport, WA
Re: AZ not so smooth on CPC 800 (pushing manually) new [Re: cn register 5]
      #5751217 - 03/23/13 05:24 AM

Great. Thanks Chris.

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lamplight
Carpal Tunnel
*****

Reged: 09/18/12

Loc: western MA, U.S.
Re: AZ not so smooth on CPC 800 (pushing manually) [Re: N7XW]
      #5752620 - 03/23/13 08:19 PM

wow.. thanks escher!

i certainly havent used it enough to wear bearings .. ive bookmarked the thread thanks for posting that whole process!


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