Fungus -- Arghhh!

I was shutting down my observatory after a nights viewing. It was 25F, so as usual, I slew my scopes over to check for any fog or ice on the objectives before placing the covers on. I noticed a very small patch of fungal branching between the objective elements of my Tak FS78 guidescope.

What's the best way to deal with this before it gets outta hand? Send it in to TNR? Deal with it myself? Or what?

Thanks for any advice.

Hi Louis,
Agreed not good. I’d get a recommendation from the manufacturer first or better yet get them to do it for you. Are you sure its fungus and not ice crystals? I’d get it dry right away using silica gel or a small low wattage light bulb 5-15 watts or a Dew Buster. Carefule not to thermal shock the elements.

Before doing this yourself get an OK and recommendation from the manufacturer because of the chemical and environmental sensitivity of anomalous dispersion glasses used in APO’s.

Anytime you touch an optic you run the risk of damaging it, no matter how experienced you are…I have used a mixture of hydrogen peroxide, ammonia, isopropyl alcohol, and RO-distilled filtered water with a small amount of surfactant to clean fungus from more robust glasses like BK7 or F2.

When you clean the lens start from the center out toward the edge and only wipe it once then discard the wipe. Final wipe can be done using an ultra pure reagent grade solvent like isopropyl, methanol or if you can get it spectrophotometric grade acetone, the alcohols are easier to use. Use little or no pressure when wiping and a bright light in a darkened room so you can see residues on the surface. Use a thick soft Tyvek clean room wipe, it will take a lot of them to clean the objective. Be sure you mark the elements spacers and housing so you can get everything clocked and orientated correctly back in the housing. Use the same care cleaning on the housing and be especially careful with surface blackening as they are often very sensitive to solvents and wiping. Be sure you have a lot of space to carefully handle the elements and keep things organized and a soft dry place to set the optical elements. Make sure the room and work surfaces are clean.

Again I’d suggest getting the manufacturer to do this for you… Best of Luck and Regards, Dave

Louis,


If you haven't seen it already:

http://www.europa.com/~telscope/fungus.txt

Interesting that fungi can grow on a "clean", almost sterile surface like glass, but they find a way. Any trace of organic contamination, even a single pollen granule will serve as fertilizer. In the past trace amounts of mercury and cadmium were used as anti-fungal additives for paint, but both are forbidden now.