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Are telescopes affected by fungus?

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orionrider

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I was thinking of buying a second hand telescope, something cheap since the 'seeing' in my area is probably one of the worst in the world. But the instruments I found were all quite old (>10 years). I'm concerned about fungus, which has effected some of my camera lenses.

Example of fungus on camera lenses:


Are telescopes more or less affected by fungus than camera lenses? Is a reflector better or worse than a refractor telescope?

Sometimes fungus can be cleaned, if it has not etched the glass. But disassembling a camera lens is often really hard, sometimes impossible (cemented lenses). Is a telescope easy to dismantle in order to clean the fungus?

Any suggestions, other things to check in 2nd hand scopes :?:
 
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MeteorWayne

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Interesting question. Never really thought about it before. If there is fungus on the primary mirror of a reflector, I would probably pass. The surface is a VERY thin layer of aluminum deposited on the glass. It should NEVER be touched by anything other than water to clean it, unless you are going to have it recoated. Even a soft brush will damage the surface. If it has been etched by a fungus, you would have to have it reground as well, not a trivial matter. Dust causes little problem until it's very thick; we have our 26" at the NJAA cleaned about once a decade, and have just had it recoated after ~ 30 years.... no fungus :)

MW
 
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orionrider

Guest
Thanks MW.

Fungus can be present and still have little effect, depending on where it occurs (edge or center). The optics on my 40-year-old 7x50 Nikon binoculars are badly affected, only the center is clear but they still perform better than most of the new fancy-colored models ;)

Since I discovered the effects of these microbes, I store all my lenses in a clear plastic container (fungus thrives in the dark). All the silica bags I get my hands on go in the box as well. Once in a while, when the weather is hot and dry, I lay the silica bags in the sun for an hour or two to 'reactivate' them. You can also buy silica that goes in the microwave.

The worst idea is to keep the optics in their original leather pouch in a dark place that is not perfectly dry, or where there is mold on the walls, fabrics, furniture,... This can cause fungus in just a few years! :idea:
 
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Fallingstar1971

Guest
Right on all points wayne, but I will add this.........

The most nasty telescope infestations come from fungus growing in-between the EP lenses in the same way your camera was affected. Yes these lenses are cemented together, and fungus will grow in the tiny space between them.

The best way to prevent this is to keep your scope protected and cared for. No basement of garage here, mine is either in my living room or in my car.

As far a cleaning, that one of the most common ways to damage optics. Do some research, it CAN be done, but you may want to enlist the aid of some people that have done it before. I have a post kicking around here with step- by-step instructions from some university, but it is still a long and painstaking process. Not very complicated, its just like wayne said, molecule thick coatings can be scratched all to easy. So its all about time and patience.

Welp, off to work I go. Perhaps I can get some time in tonight......who knows

Star
 
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Woggles

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orionrider":2y4ntzd5 said:
The worst idea is to keep the optics in their original leather pouch in a dark place that is not perfectly dry, or where there is mold on the walls, fabrics, furniture,... This can cause fungus in just a few years! :idea:
Thanks for bringing up this question Orionrider. I keep a pair binoculars in my boat in a leather pouch. I won't be doing that now!!!
 
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orionrider

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Woggles":2pgrqnwq said:
I keep a pair binoculars in my boat in a leather pouch
If you have Marine binoculars, they should be air(water-)tight. I know some are filled with nitrogen, maybe yours are?

Fungus typically affects old (>10y) lenses, so we won't know for a long time if modern optics are at risk. Maybe the formulation of the coatings and cements has changed to take that into account.


Thanks Star, I will stay away from 2nd hand refractors if I'm not sure they are 100% fungus-free. ;)
I suppose a reflector would be more 'fungus-resistant', except for the eyepiece :?:
 
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Fallingstar1971

Guest
If the optics are good, then it should be ok.....in my experience, the lower the quality, the greater the chances for fungus. The cement is a key factor. In higher quality EPs, the fungus cannot get in between the layers of the lens. This is because they use a higher quality cement. Surface fungus...at least with that there is a chance that it can be cleaned/repaired. Once the fungus gets in-between the layers you might as well trash it.

I would not let that discourage me from used equipment however, especially if you have the opportunity to examine the hardware up close. There are still deals to be had. You must consider many people that put these up for sale got them as gifts and will sell them for way cheaper than buying new. You already know what to look for, so just keep an eye out.

Best of luck

Star
 
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orionrider

Guest
Thank you Star.
I am looking at used telescopes because many US companies don't sell internationally and the new prices in Europe are about 50% higher :cry:
 
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