Author Topic: Coulter 13" mirror removal  (Read 1454 times)

astropoyson@sbcglobal.net

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Coulter 13" mirror removal
« on: August 29, 2016, 10:22:43 PM »
I need to remove the mirror from my 13" Coulter for re-aluminizing.  It's not real obvious how the mirror is held to the (probably particleboard) "cell".  Anyone have personal knowledge, trustworthy second hand or (oh well), good sounding rumors as to how those mirrors were fastened in?

There are no clips, no classy n-point cell, so I suspect it was glued in by RTV which was famous about that time.  I've thought of a sledge hammer, but at my eight decades of age it's hard to justify buying a new mirror.  I'd like to get this scope in shape to entice a family member to Astronomy.

Thanks for your thoughts. 
Robert

John Pierce

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Re: Coulter 13" mirror removal
« Reply #1 on: August 29, 2016, 10:39:55 PM »
this is a red tube Couter ?   My 10.1" red tube, the mirror was glued to the partical board base with 3 disks of some sort of cheese cloth, and a glue remarkably similar to Duco cement.    Acetone melted the glue like hot water on sugar.   I think there were foam pads too.   I'm sort o remembering using a steel wire 'garrot' to slice the foam disks, then using acetone to clean glue traces off the mirror.   I initially reattached the mirror to the particle board disk using silicone aquarium sealer in 3 1" diameter disks about 2mm thick, but this came unbonded from the particle board after a few months of trips in my Volvo wagon.   I then replaced that particle board with a baltic ply disk but was never happy with it, and finally got one of Mark Wagner's wonderful mirror mounts, and got rid of all that heavy particle board entirely.   this significantly lightened the back of the tube, so I had to move the altitude bearings up the tube a fair bit (also due to having added a finder scope + telrad + real focuser, and using larger/heavier eyepieces than were likely common in the mid 80s when these red-tube Coulter's were made).   Also I had to move the mirror up the OTA a inch or so to achieve focus with the orion cheap crayford style focuser I'd used.


astropoyson@sbcglobal.net

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Re: Coulter 13" mirror removal
« Reply #2 on: September 16, 2016, 08:16:04 PM »
Thanks for your reply, John.  Yes, my tube was originally red -- my artist wife dislikes red, so she did a wonderful abstract impression of the night sky.  Now it stores in the family room.  :)  I have done some upgrades also:  JMI electronic setting circles, focuser, finder(s), system of weights with velcro to adjust for light to heavy EP.  Still using the particle board mount, but have modified the azimuth and elevation bearings.  I keep thinking I will build a new mount from baltic birch,  but work on my 8" home built instead as that mirror's figure is excellent and it's on a motorized mount.  What brand name is Mark using for his mirror cells?

John Pierce

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Re: Coulter 13" mirror removal
« Reply #3 on: September 16, 2016, 09:15:27 PM »
mark's business is www.astrogoods.com ... but I don't know if the style I have goes above 12"... 

Jrgose

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Re: Coulter 13" mirror removal
« Reply #4 on: September 22, 2016, 04:21:26 PM »
Ref. your mirror, if you bring it to one of the nearby clubs I suspect you'd get a lot of hands on advice;)  Even at a club meeting, if you coordinate ahead of time. One club has a dedicated scope fix-it days.