Be aware the primary mirror cell, with the mirror inside, may be really HEAVY. Don't try this
procedure while you are alone. Use the proper lifting equipment, if needed.
In all telescopes, there are electric connections inside. Gently unplug them while you
remove the cell, and remember to re-plug them while you reassemble the cell in place.
The number, position and "look" of the screws that fix the primary mirror cell to the tube
may vary with the size and optical configuration of each scope, but such screws are always
a very regular "crown" around the optical axis. Because of the big number of screws, there
is no risk of misalignment when removing or reassembling the primary mirror cell.
Two different "backs" of
Officina Stellare tele-
scopes. As you can see,
the screws that fix the
primary mirror cell to the
tube look different (green
arrows), but the symmetry
of their arrangement
around the optical axis is
obvious.
Procedure:
The mirror itself is made of glass, so it is very hard. What is delicate is the surface coating
(aluminum, silver, or gold, plus protection coatings, depending of the telescope purpose). Since
any kind of dust does contain some microscopic piece of "sand", the risk is to scratch the coating,
not the mirror.
When you wash a small mirror, you simply remove it from the cell and put it in the sink. Then you
blast it with water. The mirrors of
Officina Stellare
telescopes are too big to operate this way, and
we suggest
not
to remove the mirror from the cell. So we will describe the procedure to wash the
mirror
without
removing the mirror itself from the cell, but just removing the cell from the scope, as
described above.
1. Remove the cell+mirror assembly form the tube, as described above.
2. From now on wear LATEX GLOVES AND A MASK.
3. PROTECT THE LIGHT SHIELD AND THE ELECTRONICS USING KITCHEN
TRANSPARENT FILM. Try to leave only the mirror exposed. The paint over light shields is
really delicate. Don't touch it with naked hands.
4. Put the cell+mirror assembly horizontally (i.e. optical axis parallel to the ground), and
provide some way to drain the water you will blast on it.
5. Use an air blast (from an air can or from a compressor) to blow the bigger dust away. DO
NOT USE BRUSHES – only air.
6. If the mirror looks good enough to you, stop here and reassemble the cell in place.
Continue this procedure only if you have dust that remains attached to the mirror, or you
have "greasy" dirt (fingerprints, resin droplets).
7. Mask, if needed, electric or mechanical parts with paper tape to protect the from water
blasts (if needed, you can stick the paper tape to the
side
of the mirror, obviously
not
on
the reflective surface).
8. Use the water atomizer (loaded with distilled water) to produce small "jets" of water against
the reflecting surface of the mirror. The cleaning action is purely "mechanical", i.e. is the
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