Last updated: 4 February 2003

Subject:	40 mm Eyepiece Damage from Hair/Dew Dryer?
Sent:	Monday, February 3, 2003 6:45:06
From:	rmuller@pirouline.com (Robert Muller)
Thanks for the site, it's a wonderful service you provide.

I was observing in Destin Florida Sunday morning and when I got up at
4:30 am to view Omega Centauri (among other things) I of course found
allot of dew.  For the first time I got out a hair dryer (on low,
carefully) to warm the scope and eyepieces.  Everything was ok except
the 40 mm took a while to clear, especially between the optics inside
the eyepiece. The next morning when I put things up I noticed crazing
and mottling in my 18 month old 40mm Meade Super Plossl eyepiece.  I
disassembled it to insect it closer and found the crazing and mottling
on both of the flat surfaces and actually a chip of glass fell out as
the edge of the upper/outer optic was chipped.  I had never noticed this
before however I am not sure I have ever looked at it this carefully
either. Considering it's condition I tried to clean the optics using a
kit I got from Clay Sherrod and the problem was even more apparent.  I
am not aware of ever dropping or mishandling it in any way.  Could this
have been caused by the dryer or maybe is it a factory defect just now
showing up? This is my first scope and have had it 2 years but I am not
experienced enough to know if maybe it was defective all along.  Any
thoughts would be appreciated.

Robert Muller
Jackson, MS
Mike here: Using a hair dryer is a bad idea. Sorry. I suspect the problems you noted were indeed caused by heat stress.


I guess that would be thermal expansion causing the break, and the heat
baking the coatings right?

I read about doing this.... are the dew dryers lower heat or did I just
over do/undew it (hahhah).  Might as well joke after ruining a nice $100
eyepiece.  Being on the coast on a cool night, the dew was very bad, and
it was my only night to observe. I was on a 2nd floor deck and dew was
dripping off from the metal roof behind me.

You might in your response on the post talk about strategies to address
this.  Isn't one solution to get a small heater and blow it over the
scope during the evening, when you are near a power source like I was? I
look forward to seeing the post.

Thanks again for your thoughts and condolences..

Robert Muller
Mike here: I would not recommend any commerial hair dryer for this purpose. The best solution is to not let dew form (by use of dew prevention devices). If dew does form then the best solution to deal with it is to let it air dry in a clean environment.

Return to the top of this page.

Go back to the Warnings Page.

Go back to my ETX Home Page.

Copyright ©2003 Michael L. Weasner / etx@me.com
Submittals Copyright © 2003 by the Submitter
URL = http://www.weasner.com/etx/warnings/hairdryer.html