Below is one possible way to remove and re-install a Meade secondary.
Place two stacks of books on the table and lay a clean towel over
Obtain a small hex wrench ( Allen wrench ).
Make an index mark with a black marking pen if desired.
Remove the screws from the correcting plate retaining ring.
With a clean towel place the correcting plate with the secondary
mirror facing down between the books.
Cover the tube with foil or plastic wrap.
Remove the three secondary adjustment screws. The secondary will
fall onto the towel.
Wrap the secondary in a small clean towel for shipment via U S Mail.
Retain the parts for reinstallation.
The tricky part of re-installation is reinstalling the secondary in
its well without touching the
easily damaged new coating.
If possible find someone with steady hands to help.
And you will need a small mirror, possibly a mechanics adjustable
mirror and a clean 'Q' tip.
Holding the correcting plate and the secondary with clean towels
insert the secondary sideways
back against its center fulcrum
pin. Then tilt the plate so the secondary is facing up.
One hex screw should be on the long end of the hex wrench.
Have your helper hold the correcting plate with the clean towel and
you gently rotate the secondary
on its fulcrum pin using the 'Q'
tip. Looking in the mirror on the table watch through one
of the adjustment screw holes
until the tapped hole in the secondary plate lines up.
Then start the first screw.
The remaining two screws are then relatively easy.
Re-install the correcting plate into the telescope with the index
marks aligned, if present.
Remove eyepiece and right angle adapter from tube bottom if present.
Put a solid color towel over the top of the tube with a light behind
it and look into the bottom of the tube.
When you are relaxed and have some time adjust the three adjustment
screws until when looking through
the center of the bottom of the tube all the mirrors and
reflections of mirrors appear to be concentric.
To get the adjustment screws snug with the optics in alignment will
take some patience.
While doing the adjustment be sure not to loosen the adjustment
screws too far or the secondary will fall onto the primary.
For a more detailed collimation method using an
artificial star refer to 'Sky and Telescope'
February 2018, page 28.
Re-attaching secondary to backing plate
We no longer remove the secondary from the aluminum
back plate during re-coating unless there is some unusual reason for
If a mirror is attached to a metal back plate the adhesive can be softened
by soaking overnight in regular paint thinner. Then slip the edge of a
utility knife blade between mirror and back plate to gently separate them.
If using 'Silicone I' you can probably cut the sealant without soaking.
Or otherwise slip the blade of a hacksaw between mirror and wood back plate to
saw the sealant. Keep metal tools away from the mirror face.
De-coating without separating the diagonal is often possible.
mirror from its backing plate
It may not be possible to separate the
mirror from its backing plate if the customer did not space the mirror off
the backing plate or if some type of super epoxy was used instead of the
elastomer. (Silicon sealant type I or similar.)
With the wood backing
shown it will not be possible to coat the mirror attached to the backing
because it will not be possible to attain the required vacuum for coating.
More 'how to'.
When gluing mirrors to their mirror cell be sure to allow the sealant to
Update, July 8, 2018
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