? My 23 year old 20” F5 has always been kept in a controlled environment, but are starting to fail. ?Do you have any mirror coating companies that you could recommend?

Rick Markunas

On Nov 20, 2020, at 11:20 AM, Dragan Nikin <dragannikin@...> wrote:

?

A repost from Obsession FB group.

Sorry this will be kinda long.

Some good news I want to share. Anyone that knows me personally knows that I haven't observed regularly with my 25" or 30" in a number of years - 5 to be exact. I'll blame 'life' for this little absence. Yes, I've gotten out to observe fairly often, particularly in Ft Davis with a 48 and atop Mauna Kea with a 22, so I'm really not complaining. My scopes were in storage during this time, protected sufficiently - or so I thought. When I brought the scopes home and wanted to get them prepared for regular observing, I discovered that the primaries were covered in a 'caked on' layer of gray dust. They didn't look good at all.

Fearing the worst, a bath was in order. I pulled out the 25's mirror yesterday and proceeded to wash the mirror just as Dave does. After the initial rinse, i proceeded to use soapy water and cotton hoping to remove the film. The cotton actually turned gray - that's how bad the scum was. After numerous washings with soapy wads of cotton, the film did not come off. After far too many vulgarities, I resigned myself that it's time for a recoat and I should just dry it and move on. Well, lo and behold, as soon as I began drying the mirror, the disgusting film started to come off! What a surprise!

Now, I'll be honest. The mirror doesn't look like it just came back from the coater. But it looks great and it's definitely usable and I've bought myself atleast a few years of use! I'll need a recoat for sure but it won't be now. And that's all that matters! I'll do the 30 tonight after work and report back. I'm sure I'll have the same results.

Now, for the teaching moment. Normally, when my scope lived in its trailer, I religiously kept a 15w lightbulb underneath the mirror. For those who don't know, this helps keep the mirror warmer than ambient during storage in an enclosed container helping prevent dew from forming on the primary.

During my hiatus, the scopes lived in a relatives garage. Although the scopes were covered with plastic and blankets, that wasn't nearly enough protection. I also didn't think I needed to do the light bulb trick in a large garage so I didn't do it. BIG MISTAKE. 5 years of storage and all of the heating, cooling, dewing cycles took its toll. Never will I make this mistake again. My laziness essentially caked on 5 years of dust and whatever else in the form of airborne contaminates.

So. Please learn from my mistakes. If you're going to store your scope in anything other than a controlled environment, please use the time tested lightbulb trick. It very well could save your coatings.

I just got really lucky.....

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