[Chaos-l] Fwd: [UncensoredTakGroup] Re: Help! TOA130 lens coating problem

[E. Allen Davis]

THIS is a forward from a thread on the Tak group about damage to lens coatings.  



Interesting what the follow up says about use of DEET etc. 



i also know from personal experience that anything with alcohol can damage mirror coatings.  i used some cleaner years ago on my mirror and it caused a bluish haze with a certain part of my mirror.  seems the alchohol bonds with compounds in the coating. 



This is one reason I always spray DEET on a paper towel and rub it on skin.  I don't ever spray insect repellant near the scope or eyepieces.  thankfully we are out of mosquito season for a little while.  i actrually hope we get some colder weather this year to help with bug populations next year. 



just some interesting info...i feel sorry for the guy with the TOA 130  allen 


E. Allen Davis 
 starstorm151 at embarqmail.com 

 "M'Illumino              "I am enlightened 
 D'Immenso"              by the immensity." 

   -Ungaretti               -Ungaretti 

----- Forwarded Message -----
  




The problem doesn't appear to be the result of abrasive cleaning. It 
appears the coating was exposed to a chemical of some sort. I did a little quick research and discovered that the chemical component of insect repellent DEET (diethyltoluamide) can damage lens coatings. Also, some folks use moth balls to dissuade insects from getting into their equipment bags and cases. Moth balls contain the chemical compound 1,4-dichlorobenzene (para-dichlorobenzene, p-dichlorobenzene, or PDB) which can damage lens coatings. 

Alternatively, acids have a damaging effect on optical coating as well. Using optical equipment in proximity to chemical plants or near industries that utilize acidic compounds in manufacturing, there is a probability of acidic emissions resulting in acid rain or acid dew. If this comes in contact with coated optical systems can result in damage over time. Lens coatings are intentionally removed using acid, but usually this results in damage to the optics and requires replacement. 

Not a solution to your problem, but could shed some light on your issue. 

Scott Busby 
Belmont Observatory 

--- In UncensoredTakGroup at yahoogroups.com , "mackey" <hojong.lin at ...> wrote: 
> 
> Don't really know what happened. My friend noticed strange 'scratches' on 
> his TOA130 objective lens. Here are some photos: 
> 
> http://farm9.staticflickr.com/8194/8137649431_b27d3191bb_o.jpg 
> http://farm9.staticflickr.com/8473/8137649357_b440c6c1f2_o.jpg 
> 
> He can't recall any sandy wind incidence which may be the culprit. 
> 
> Pictures of bright stars also showed ugly spikes: 
> 
> http://farm9.staticflickr.com/8308/7941835164_f251c3b71f_o.jpg 
> http://farm9.staticflickr.com/8439/7984289825_33e00f2bdb_o.jpg 
> 
> Anybody knew what might seem to be the problem? 
> 
> Thanks for any info. 
> 
> Hojong Lin 
> Taipei, Taiwan 
> 


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