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Help for removing C8 secondary

Beginner Catadioptric Celestron Collimation
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#1 Waynerplays

Waynerplays

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Posted 26 September 2022 - 04:10 PM

This screw seized when collimating due to rusted threads and I badly stripped the hex socket. I contacted a Celestron tech who responded as follows after failing using methods I researched that I dare try. 
 

“If the WD40 trick does not work, or the Philips heads are too rounded out, the next options are a little brutal.
After marking the orientation of the corrector plate and removing it, also mark the orientation of the secondary mirror(??) 

Where do I mark it? I see one at 12 o’clock on the top of the sleeve around the mirror but not on the mirror. 

Using a Dremel hand grinder with a small abrasive bit, you can slowly grind the heads off of the Philips screws. I say slowly so they will not overheat and melt the plastic in the center secondary support.
Once all three screw heads are ground off, the screw studs can be pulled through the secondary support as the secondary mirror is removed from under the corrector(??)

does the mirror and its backplate detach and drop down through the baffle? If so how does one align the screw holes when reassembling as follows?

 

The remaining screw studs can then be removed by grabbing them with small vicegrip pliers. (just one screw head to grind off and two to unscrew) 

After cleaning the threaded holes with a tap, the screws can be replaced with the proper size screw”.

If you’ve removed a secondary before I sure could use some direction 

 

thanks and clear skies

Wayne

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#2 SgrB2

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Posted 26 September 2022 - 04:31 PM

Watch this video about how to remove the corrector plate.

The video tells you much more that you don't need because

it is how to install a HyperStar conversion kit.

 

https://www.youtube....h?v=GXA7X5G_Ml8

 

 

Cheers,

SgrB2



#3 lattitrail

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Posted 26 September 2022 - 04:49 PM

Are those hex heads? They look like torq head screws. If you can get a torq head to fit, it may come out where the hex failed.

 

Many screw removal tactics probably won't work on a fragile telescope as they involve heat, welding, or grinding. If you can't get the screw to break free, you may have to resort to slowly drilling out the screw and then re-tapping the hole.



#4 Waynerplays

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Posted 26 September 2022 - 07:10 PM

Are those hex heads? They look like torq head screws. If you can get a torq head to fit, it may come out where the hex failed.

 

Many screw removal tactics probably won't work on a fragile telescope as they involve heat, welding, or grinding. If you can't get the screw to break free, you may have to resort to slowly drilling out the screw and then re-tapping the hole.

I’ve ground off the head off the only seized screw but the other two hex socket screws are still fine. Once removed I should be able to slide the stud through the exterior support and use grips to unscrew it. 



#5 Waynerplays

Waynerplays

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Posted 26 September 2022 - 07:15 PM

Watch this video about how to remove the corrector plate.

The video tells you much more that you don't need because

it is how to install a HyperStar conversion kit.

 

https://www.youtube....h?v=GXA7X5G_Ml8

 

 

Cheers,

SgrB2

Great SgrB2. A lot more to go on than I had found. Thanks!




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