water jet that does remove the dust. There is no "chemical" action at this stage. You will
use something else than water only if needed (see below).
9. Clean all the mirror 2-3 times with water jets. Rotate slowly the mirror and blast only the
"lower" half, to facilitate the drain of water. Tilt a bit the mirror so that the water flows in the
drain without the risk to touch electrical or mechanical parts of the cell.
10. After this "shower" your mirror is probably clean enough. Just let it dry in open air. Use a
hairdryer to speed the process, if needed. Keep the hairdryer at least 40 cm from the
mirror. If the temperature of the air flow can be regulated, use the lowest setting.
11. Should you have fingerprints, resin droplets or other "greasy" dirt on your mirror, use a mild
dish detergent, heavly diluited with distilled water (100:1) and pour it on some sterile
cotton. Wear latex gloves to avoid the grease from your own skin. Gently DUB (and not
RUB!) the mirror surface with the cleaning solution. Change often the cotton.
12. Wash the mirror again with plenty of water jets from the atomizer, like in step 8 and 9. Let it
dry in air or with the hairdryer.
Remember. If the water jets are not enough, the general idea is to "dub without rub" with the
detergent solution. Rubbing (even as gently as you can) will almost surely leave some scratches
on the mirror coating. Generally speaking scratches are not a problem – a mirror will work fine
even with dozen of them – but the problem is that a
single
"bad" scratch can create annoying
reflexes when imaging with a bright star in the filed. If you have to act really energetically (like for a
bird poo… yes, it happens!) keep the dirt wet while rubbing (with wet cotton, gently). Grit is less
abrasive wet than dry, so "the wetter, the better". Use a lot of water!
For
secondary mirrors
, we suggest to wash them with the same procedure, but without removing
the cell from the tube. It is a good idea to wash the secondary mirror when the telescope is
pointing at the zenith, and the primary cell has been removed for cleaning. Since all secondary
mirrors are "sealed" against their cells, and you spray water upwards, there is no risk of water to
go "behind" the mirror, where the electrical parts (mirror heater and secondary mirror motor, if
installed) are located. Remember to protect the light shield with transparent film, and always wear
latex gloves.
NOTE: because of the orientation of mirrors during use, it is normal to clean the secondary mirror
only every two or three cleanings of the primary mirror.
8.4) Re-coating the mirrors
And what about
re-coating
of the mirrors? The sad reality is that there is no general rule. The
mirror coating may need to be redone every two years or so, if your telescope is located in front of
the sea, in a very polluted area, and works 350 nights every year. The same coating will last 10-12
(or even more!) years if your site is high in the mountains and in a low pollution area, and/or the
telescope is used less frequently.
If you need assistance to disassemble the mirrors from their cells for re-coating, please contact
our customer service,
because there are dozen of different cells
models, so we will e-mail you specific instrutions for your scope.
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