Cleaning a 25" mirror

(click on the pictures to view!)

This is an Obsession 25" scope and belongs to the Astronomical Society Quadrant in Finland. (Tähtitieteellinen Seura Kvadrantti r.y.)
As some of us amateur astronomers would like to own all possible gadgets and observing instruments one can think of, then usually at some point the personal funds come to end (sigh). So to get more instruments a joint effort is better than none. Within the club one can own shares to different instruments. Each share gives the right to use the equipment for one week in a given year. Most club members have their own permanent observatories and usually more than one telescope... The club is a very convinient way to fill the never ending apetite for more...
These pictures are from our annual repair meeting in 1995. This summer the main thing was to re-aluminize and coat the mirror for the next observing season. (Remember that over here summertime is a perfect time for repairs and telescope making as there are practically no dark nites for over three months!)

Okay, herīs the baby out in the open and the water hose running... are we ready?


Letīs start it easy, pour that stuff first... HEY! nothing happens, this doesnīt work at all! Okay letīs try the plumbers thing... WOW! look at it sizzle. This is too easy!
By the way, does that chemical reaction produce a lot of heat? Could the mirror crack?
(silence)
More water please! No - it is not that hot (touching). Hey! lets be realistic...

Okay - this is good stuff, lets do the whole thing.
Hmm. Whatīs with this brush???? - its melting! More water please...

Itīs persistent at the edges - some more work. Finally more water.

What a beautiful surface! So nice and clean... Hmm - by the way what is that coloring in the middle?
Propably just drying markings...
Canīt clean the markings... I wonder ??? Hmm. Well itīs in the middle, so it will be in the shadow of the secondary - so who cares?


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Juhani Kyyrö
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