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Celestron C14 factory focuser has no focus travel - what to do ?

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#1 vkhastro1

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Posted 12 November 2017 - 03:04 PM

My Celestron C14 Edge factory focuser is very tight.

I released both Mirror locks.

I try and turn the factory focuser but it only turns 1 or 2 revolutions turning clockwise and it gets tight. I reverse direction going counterclockwise and again 1 to 2 revolutions and it starts to bind?

I removed the rubber focuser knob and 3 factory screws.

Removed the original orange coloured focuser plate.

Assessed the focuser movement.

Turning clockwise, the focuser turned several times until it reached the end of its travel distance. There is a black coloured rubber gasket visible under the focuser mechanism.

Turning counterclockwise the focuser moves outward at least 1/2 or more - very smooth.) However, I noticed the entire focusing mechanism moves outward (if the orange focuser plate was installed with the 3 factory screws in its regular position, am sure this outer focus movement would bind on the inside of this focuser plate).

 

I cannot figure out what is going on.

What do I need to do to restore normal focus travel ?

Any help would be appreciated.


Edited by vkhastro1, 12 November 2017 - 03:04 PM.


#2 Eddgie

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Posted 12 November 2017 - 03:08 PM

The very first thing that you want to do is to look into the front of the corrector and ensure that there are no accesory screws that are sticking down in front of the primary mirror.


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#3 Eddgie

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Posted 12 November 2017 - 03:16 PM

I posted the last post quickly because if this condition exists, excessive force on the focuser will cause you to chip the edge of the primary mirror.  If you have not done so already, read the above post first.

 

 

If the above post did not identify the problem, then here is the next step to take.

 

If your scope is an EdgeHD, make sure your mirror locks are not locked down.

 

Make sure that your shipping screws are clear of the mirror support.   They should come completely out.

 

 

Since you already have the focuser bearing assembly pulled, here is the next thing you should do.  Grasp the focuser knob and try to turn it clockwise as far as it will go.  This would normally move the mirror forward, but if you have removed the screws that hold the bearing assembly into place, what this will actually do is cause the bearing assembly to move out from the rear of the tube.    Once you have turned the knob as far as it will go counterclockwise, the treaded rod should be visible.  Now, pull the focuser bearing out by hand and this should pull the mirror to the rear. 

 

Inspect the threads on the focuser rod to ensure there is no damage.

 

Now, press the focuser rod back in by hand.  If there is nothing restricting the mirror's forward motion, then you should be able to simply press the focuser rod all the way back in until the bearing assembly returns to it's seat.  Just screw it back in.   If there is no damage to the rod visible in the earlier check, and the mirror moved its full length, then you should be fine now.


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#4 carolinaskies

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Posted 12 November 2017 - 03:25 PM

My Celestron C14 Edge factory focuser is very tight.

I released both Mirror locks.

I try and turn the factory focuser but it only turns 1 or 2 revolutions turning clockwise and it gets tight. I reverse direction going counterclockwise and again 1 to 2 revolutions and it starts to bind?

I removed the rubber focuser knob and 3 factory screws.

Removed the original orange coloured focuser plate.

Assessed the focuser movement.

Turning clockwise, the focuser turned several times until it reached the end of its travel distance. There is a black coloured rubber gasket visible under the focuser mechanism.

Turning counterclockwise the focuser moves outward at least 1/2 or more - very smooth.) However, I noticed the entire focusing mechanism moves outward (if the orange focuser plate was installed with the 3 factory screws in its regular position, am sure this outer focus movement would bind on the inside of this focuser plate).

 

I cannot figure out what is going on.

What do I need to do to restore normal focus travel ?

Any help would be appreciated.

Did it just start doing this?  Did the scope get dropped or jarred?  You've never had any issue with the focuser acting up, sticking etc?  

The prior response to look down the OTA to make sure nothing has somehow come loose and is hampering the mirror travel is a wise precaution.  

After you've made sure nothing is stuck inside the OTA tube to cause the mirror to jam, I would attempt to move the mirror manually by pushing pulling on the attaching pin.  If it moves freely then your focuser is the issue.  If the mirror is binding, you'll need to identify if somehow the mirror got cocked on the baffle tube.  


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#5 vkhastro1

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Posted 12 November 2017 - 03:37 PM

I checked by looking through the corrector plate at the primary mirror - no screws sticking in front of the mirror.

I removed both mirror locking knobs completely off.

There is a silver coloured pin sticking out from the threaded portion - is this pin mentioned to manually push/pull ?

I tried to push/pull on this pin on both mirror locks - no movement at all.

I also turned the focuser counterclockwise to the end of its travel.

No damage to the threads.

I tried to pull it outward but no movement at all.

What next?

 

Gary


Edited by vkhastro1, 12 November 2017 - 04:02 PM.


#6 vkhastro1

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Posted 12 November 2017 - 04:27 PM

I am the 2nd owner of the scope.

No dents or other physical damage.

This may sound like a stupid question - where are the original shipping screws (that are supposed be clear of the mirror support) located ?

 

The mirror maybe angulated on the baffle ?


Edited by vkhastro1, 12 November 2017 - 04:28 PM.


#7 bikerdib

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Posted 12 November 2017 - 08:49 PM

The large Edge scopes have 2 differeng mirror locks.  There are the 2 locks intended to prevent mirror flop during use, those are the 2 black knobs that you turn with your fingers.  Then there are the transport mirror locks which are allen head screws.  These are located near where you screw on the visual back. These must be loosened before you use the focuser.  They will unscrew untill completely loose but are captured in the back casting so they cannot be lost.  You will know when they are loose because they will flop around in the casting.


Edited by bikerdib, 12 November 2017 - 08:50 PM.

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#8 vkhastro1

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Posted 12 November 2017 - 09:20 PM

The large Edge scopes have 2 differeng mirror locks.  There are the 2 locks intended to prevent mirror flop during use, those are the 2 black knobs that you turn with your fingers.  Then there are the transport mirror locks which are allen head screws.  These are located near where you screw on the visual back. These must be loosened before you use the focuser.  They will unscrew untill completely loose but are captured in the back casting so they cannot be lost.  You will know when they are loose because they will flop around in the casting.

Hi Dennis,

 

You are the man !!

I did not know what the 2 black Allan Key bolts on either side of the focuser were for (searched all the online Celestron manuals I could find no info on these 2 bolts).

I backed off the 2 forementioned Allan key bolts as you described.

Reattached the stock Celestron focuser via the 3 screws, pushed on the rubber knob.

Turned the focuser knob - no resistance .

Success, the focuser turns both clockwise and counterclockwise with no restrictions !

 

I applaud Eddgie, carolinaskies and bikerdib for all your help.

CloudyNights experience and knowledge to the rescue !!

 

I am one happy camper .


Edited by vkhastro1, 12 November 2017 - 09:50 PM.

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#9 bikerdib

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Posted 13 November 2017 - 10:44 AM

Glad to be of assistance.

 

I always rethread the 2 allen screws whenever carrying or hauling the scope.  They don't really need to be tight, just threaded in all the way. The primary mirror is a heavy piece of glass.

 

Have fun and clear skies.




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