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Musty smell when remove dew shield cap

Sky-Watcher Esprit 120ED Equipment Refractors Cleaning
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jewzaam avatar
jewzaam avatar
I've got an Esprit 120ED and noticed the other day when I took the cap off it smelled musty. Sniffing around it seemed to come from the felt. So I got some replacement and changed it all out. The old felt did stink!

But the smell hasn't gone away. I couldn't remove all the old backing tape for the felt which may be contributing, at least not from the tube. I did remove it from the dust cap and it required chemicals (goo gone) and a lot of elbow grease.

I've put 1 pound of desiccant in a mesh back inside the dew shield this morning. About the only other thing I can think to do. 

Any thoughts on what else I might do? Should I be worried?
Engaging
John Hayes avatar
John Hayes avatar
Yes, you should be worried.  Fungus/mildew/mold can grow in between optical elements and you don't want that to happen.  A musty smell is a good sign that conditions are right for mildew, mold, or fungus to grow and that's bad.  You might consider wiping every thing down with a diluted mixture of deionized water and 99% isopropyl alcohol (mixed 3:1).  Gently clean the front lens using Kleenex brand tissue (pure tissue with no additives) and then gently blow dry the whole assembly to make sure that everything is perfectly dry when you are done.  Then continue to use the desiccant.  You'll probably have to periodically bake-out the desiccant in a microwave as it becomes saturated.  Keeping everything dry is the key to preventing anything from growing.  Good luck!

John
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Björn Arnold avatar
Björn Arnold avatar
Under which conditions or how did you store the scope?

I‘m just wondering if it might help (in addition) to expose the lens to strong UV light to possibly kill anything that might have thought to start it’s evolutionary process?
(Before you try that I would like to have this idea double checked by someone with experience on this.)
I‘m using my refractor for solar observation in combination with a Herschel wedge. By that, I would assume that it’s also a round of „disinfection“ through the Sun‘s UV.

Björn
Ruediger avatar
Ruediger avatar
I am using a disinfectant UV-C lamp as a precaution once or twice a year. This kills any fungus or any other macrobiotic life within one minute. Don't use it longer, since ozone is generated. Its aggressive. Do it outside or well ventilated.

Of course this works only, where the light can reach the germs / spores directly. As John said, when the fungus has crept into any tiny opening, it gets very hard. In this case complete tearing down and cleaning is the last resort. You have to get get rid off any "nests", otherwise it will be back very fast.

I'll keep my fingers crossed you will win the fight!

Rüdiger
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andrea tasselli avatar
andrea tasselli avatar
Until fungus grows and grows enough to be visible you shan't be too worried. In my experience it only occurs in glued/oiled lens system.
Ruediger avatar
Ruediger avatar
andrea tasselli:
Until fungus grows and grows enough to be visible you shan't be too worried. In my experience it only occurs in glued/oiled lens system.

Sorry but I disagree completely. When you smell it, it is a prove of evidence that there are huge amounts of spores (already) in the air. That means, the complete tube is seeded and contaminated. As soon as there is the slightest nutrition for the fungus, it will explode. The earlier you take action, the likelier it is you can rescue the optics.

When you see something, it is too late! Then the lens/coating is (very likely) already damaged. Additionally in the beginning you only see the fungus mycelium only under a microscope.
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andrea tasselli avatar
andrea tasselli avatar
Not in my experience. And I've seen some pretty fungi out there…
jewzaam avatar
jewzaam avatar
Björn Arnold:
Under which conditions or how did you store the scope?

I use the scope in my back yard, setup overnight. Never had any rain incidents. It's pretty humid here and I use a dew strap with a powerbox advanced. I bring the OTA inside, it's never left out in the day. 
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jewzaam avatar
jewzaam avatar
Sounds like a uv lamp as a precaution is worth it. Thanks everybody! More tips of course are welcome. 

Regarding desiccant, yes I'll refresh it as needed. Been using this kind with 3D filament storage for years 😁
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jewzaam avatar
jewzaam avatar
Ruediger:
I am using a disinfectant UV-C lamp as a precaution once or twice a year. This kills any fungus or any other macrobiotic life within one minute. Don't use it longer, since ozone is generated. Its aggressive. Do it outside or well ventilated.

Curious if you can recommend a specific lamp.  I'm looking into them and there's quite a spread.  I wonder if a small "flashlight" style might be better as it could be easily pointed at any specific locations that might be hard to get with a larger device.  Of course, there's more risk to me if I can't walk away so will use gloves and probably UV blocking goggles, though I haven't started digging into that space.  Thinking something like this, though with Amazon.. never know.  https://smile.amazon.com/dp/B08TB32JJN
Björn Arnold avatar
Björn Arnold avatar
I use the scope in my back yard, setup overnight. Never had any rain incidents. It's pretty humid here and I use a dew strap with a powerbox advanced. I bring the OTA inside, it's never left out in the day. 
​

So far that sounds all good. Leaving it out during the day isn't necessarily an issue. Many people have it out permanently. The important thing is to get and keep it dry.

When I bring my scope inside and the lens doesn't show obvious signs of dew, I put the dustcap on while the scope's outside. Let it sit on the table for a few hours so that the temperature of the scope has climbed enough to not attract any more water and then open the dust cap and let it get dry.
For longer term storage, I'm placing the scope in a downstairs room where I'm using a dehumidifier. It keeps the rel. humidity always below 60% (even in humid summer months it's mostly 55%) usually at an average of 50%.

Maybe your storage conditions aren't ideal?

Björn
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Ruediger avatar
Ruediger avatar
Ruediger:
I am using a disinfectant UV-C lamp as a precaution once or twice a year. This kills any fungus or any other macrobiotic life within one minute. Don't use it longer, since ozone is generated. Its aggressive. Do it outside or well ventilated.

Curious if you can recommend a specific lamp.  I'm looking into them and there's quite a spread.  I wonder if a small "flashlight" style might be better as it could be easily pointed at any specific locations that might be hard to get with a larger device.  Of course, there's more risk to me if I can't walk away so will use gloves and probably UV blocking goggles, though I haven't started digging into that space.  Thinking something like this, though with Amazon.. never know.  https://smile.amazon.com/dp/B08TB32JJN

There are plenty on the market. You should get a quality one to ensure that safety regulations are met. UV-C can do harm, to humans too. I have one with gas-tube lamp, which emits strongly, but there are also small one like pens which are using LEDs, where I am not so sure how powerful they are. Usually lamps coming from the medical sector are trusty worth.

BTW: A glass fungus needs more than 70% humidity and more than 15 degree to grow. So silicate is good thing anyway.

CS
Rüdiger
jewzaam avatar
jewzaam avatar
Björn Arnold:
Maybe your storage conditions aren't ideal?

Maybe how I cap the scope. I simply put the cap on while it's outside. Dew control is still on. Inside relative humidity is typically 50%. I probably should leave it open a while inside then cover it. Thanks!
Björn Arnold avatar
Björn Arnold avatar
Maybe how I cap the scope. I simply put the cap on while it's outside. Dew control is still on. Inside relative humidity is typically 50%. I probably should leave it open a while inside then cover it. Thanks!

Yes, that's likely the problem. When you place the cap, you trap the climate in the dew shield. Even if the lens has no condensation on it, the dew shield may have (in the inside).
It's ok to place the cap on outside if you have to expect that bringing a cold scope indoors is likely leading to more dew, but once that's no longer the case, you have to remove the cap and wait until all moisture is gone.
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