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Ext 125 with fungus on primary and secondary mirrors

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#1 overland

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Posted 28 November 2021 - 06:57 PM

I recently picked up a new and unused Etx 125 with tripod and mount. Everything's in excellent condition--except the optics on the OTA. It looks like there's some fungus growing on the edges of the primary, and a little patch in the secondary. Is there anyway to clean these mirrors without ruining them?



#2 maroubra_boy

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Posted 28 November 2021 - 07:12 PM

overland,

 

BE CAREFUL HERE!!!

 

First, there is a way to clean them, HOWEVER you need to take precautions when dealing with the infected item as you don't want the fungus spores to spread to other optical gear you have.  I wouldn't be opening up even the back end plug that takes the diagonal either.

 

The optics can be cleaned, but this still leaves the fungus and spores that remain unchecked inside the OTA.

 

The fist thing to do is to put the scope outside with it facing the Sun - as this will be done outside remove the rear dust cap/plug or it will melt.  Do this for a few hours as the UV will kill the fungus on the optics.  Have a spray bottle with isopropyl alcohol handy for when you open up the OTA you will need to spray all the surfaces before anything else, including the optics.  Don't be shy with the stuff as its effectiveness depends on the dose and time of the exposure to the isopropyl.  Make it too light a spray and it evaporates before it is effective in killing the spores.  As this stuff evaporates quickly, it's a good idea to repeat the spray several times to be sure.  This is to help kill any remaining fungus that is hiding in the nooks and crannies inside the OTA.  Then you can clean the optics once the Isopropyl has dried off.  There is plenty of info on how to clean Cat optics on the Net.

 

Just be careful when opening up the OTA to not do it in the same room as you keep any other optics, scopes, eyepieces, cameras, etc.  Cross contamination needs to be controlled.  Wear gloves when opening up the optics and spray the gloves too after you've done the insides of the OTA and dispose of the gloves in the bin straight away.  Not a bad idea to spray the outside of the OTA after handling it too before removing the gloves.

 

There may be others who could suggest other ways of dealing with fungus, so it is worth reading their posts too.  No matter which way you go, cross contamination needs to be carefully controlled or you just spread the blasted fungus.

 

Alex.


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#3 sevenofnine

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Posted 28 November 2021 - 08:11 PM

Pay attention to Alex! I lost a whole bag full of camera lenses due to fungus. At best, all you can do is stop the damage. At worst, it spreads foreheadslap.gif



#4 maroubra_boy

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Posted 28 November 2021 - 09:00 PM

PS:

 

The box/case/bag that the scope came in - you need to dispose of it!

 

You cannot clean these out to a satisfactory degree, so the only option here is to put it in the bin.

 

If you've cleaned the scope to disinfect it, DO NOT PUT IT BACK INTO THE SAME CASE!!!!!!!!  You will only reintroduce the fungus to the OTA as the case will be packed full of the spores.

 

And certainly do not keep that case in the same room that you keep your other optics in for the same reasons of infection control.

 

Sorry, but fungus is not an easy thing to control once it gets into optics, and you MUST think of this more than just the item but also everything that has come with it.

 

You will also need to disinfect ALL the accessories that came with the OTA, dust caps, finder, diagonal, eyepiece and eyepiece caps, power cords, dovetails, and yes the mount too!  EVERYTHING NEEDS TO BE DISINFECTED.

 

Alex.



#5 cookjaiii

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Posted 28 November 2021 - 09:06 PM

A picture would be helpful.  Your description could apply equally to some coating loss and not necessarily fungus.

 

There have been a number of threads here devoted to discussion of fungus growing on optical surfaces.  Take-away message:  fungus thrives in warm and humid environments. 

 

It's good to be careful about cross-contamination, but fungal spores are everywhere, and fungus won't grow without a supportive environment. 


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