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Thread: Replacing the focuser tube on a reflector

  1. #1
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    Default Replacing the focuser tube on a reflector



    A portion of the aluminum focuser teeth on my Meade 127 NT got ground down after only one session last year:



    This is right at the point where stars and plants come into focus, so I had to push-pull the focuser by hand when using this scope since.

    I bought this Meade 127/1020mm (F/8) Newtonian a few years back from a seller who said he used it only once or twice after buying it new - the scope was available from Meade in 1997-1998 only (before being discontinued). Age and grease probably contributed to the softening and disintegration of the aluminum teeth.

    Finally found a new 2” replacement focuser from Telescope Warehouse. Ordered it Wednesday and finally arrived on Saturday, so I immediately went to work:



    Had to take out the secondary mirror and vanes to unscrew the focuser mount from the OTA. Was able to get the aluminum focuser tube out of the mount and put the new one in. I also took apart the secondary and primary mirrors, checked them out, and put them back onto the OTA again:



    Recollimated the mirrors and then tested the new focuser tube on the focuser:



    Racking the new focuser in and out, movement was not smooth, but rough. Still, it was better than what I had before. Now I need to give it a test run on the night sky.
    Terry
    ------------------------------------------------------------------------------------------------------------------------------------------------------------
    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

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    Default Re: Replacing the focuser tube on a reflector

    Nicky executed Terry! Is this a crayford focuser?
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    Default Re: Replacing the focuser tube on a reflector

    Quote Originally Posted by Bigzmey View Post
    Nicky executed Terry! Is this a crayford focuser?
    Thanks Andrey!

    It's a simple rack and pinion focuser that came with the scope. A Crayford on this scope would be nice, but don't think its possible without having to drill new holes in the OTA.
    Terry
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    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

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    Default Re: Replacing the focuser tube on a reflector

    Well done! So it fitted like a glove!
    terrynak and burris like this.
    Telescopes in Schiedam : SW 150 F/5 Achromat, SW Evostar 120ED F/7.5, Vixen 102ED F/9, OMC140 maksutov F/14.3, SW 102MAK F/13 on Vixen GPDX.
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    Amateur since 1970.

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    Default Re: Replacing the focuser tube on a reflector

    Nicely done Terry! Nothing like keeping it original, and nothing wrong with a good R&P either Actually, the only crayford I have is on my 10".

    A 5" at f/8, nice! I never even knew Meade made one. Seriously, how many scopes do you have?? Looking forward to the next treasure...

    All the best,
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    Skywatcher 10" Dob, SLT102, C80-HD, Vixen-made C80, Vixen A70LF,
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    Default Re: Replacing the focuser tube on a reflector

    Quote Originally Posted by John Baars View Post
    Well done! So it fitted like a glove!
    Thanks John! Yes, it worked even better once I reattached a small corrugated strip between the focuser mount and tube. Fell out the first time I replace the old focuser with the new.

    Quote Originally Posted by TheFatKitty View Post
    Nicely done Terry! Nothing like keeping it original, and nothing wrong with a good R&P either Actually, the only crayford I have is on my 10".

    A 5" at f/8, nice! I never even knew Meade made one. Seriously, how many scopes do you have?? Looking forward to the next treasure...

    All the best,
    Thanks Mark. Nice to get the focuser replaced - had to take out the focuser a second time to insert a buffer strip between mount and tube that fell out during my initial replacement.

    A 5" Newtonian with a spherical mirror needs at least an F/8 to give satisfactory images, according to Rayleigh's criterion.
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    Terry
    ------------------------------------------------------------------------------------------------------------------------------------------------------------
    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

 

 

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