Telescope fungus that "eats" glass

[MarkS]

A friend of mine keeps his apochromat scope in his observatory.  Unfortunately the objective lens element has now suffered an attack of fungus, causing irreversible damage.  The damage is caused because the fungus secretes an acid in order to digest its food (it eats dust and greasy deposits on the optical surface) and this acid etches permanent scars into the specialised optical glass.  The fungal spores germinate under humid conditions and they spread out tendrils in search of more "food" giving a very characteristic shape.  Camera lenses can be similarly affected.  The dustier and greasier the optical surface, the more "food" it has available and the more effectively it will spread.

Some background links:
http://www.truetex.com/lens_fungus.htm
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3693808/Main/3688418
http://lenses.zeiss.com/camera-lenses/en_gb/website/service/fungus_on_lenses.html

If you do a Google image search for lens fungus you will find many good examples.

Beware of damp conditions and beware if buying a second hand scope.

Mark

[Carole]

Scarey.  Glad I have a dehumidifier in the Osby which I run at 60% in the winter, also it is reasonably light in the daylight due to the light dome. 

Carole

[MarkS]

... also it is reasonably light in the daylight due to the light dome. 

But with lens caps on, the lenses are kept nice and dark - possibly humid as well from trapped dew during imaging.  They recommend exposing scopes to direct sunlight from time to time because UV kills fungus.  Don't point the scope directly at the sun, obviously.

[Fay]

Dont like to panic..............but dusters at the ready!!!!!!!!

[Carole]

But with lens caps on, the lenses are kept nice and dark - possibly humid as well from trapped dew during imaging.

Yes, thought of that while I was out this morning. 

Note to self:
Eeek, let lenses dry out well before putting lens cap on

Carole