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Meade ETX-125 corrector plate cleaning?



 
 
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  #1  
Old August 30th 03, 10:15 PM
JD
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Default Meade ETX-125 corrector plate cleaning?

While out viewing Mars last week, my Meade ETX-125 corrector plate got a
pretty good dose of dew over the course of the evening. I let the scope
thoroughly dry and upon inspection the next day, the corrector plate had
a somewhat mottled appearance. Nothing serious, but enough to make me
want to get it back to the pristine condition it was in when it was new.

Anyway, per Meade's instructions, I mixed a solution of distilled water
and isopropyl alcohol to make a cleaning solution. Then using a small
amount of solution and a microfiber towel, I proceeded to 'clean' the
corrector plate. It appeared that the solution was removing more than
the accumulated dust and dew spots- almost like it was removing the
coating on the plate. At this point I was committed to the task so I
proceeded to finish cleaning the entire outside surface of the corrector
plate.

Now, when it is completely dry and 'clean' (?, no more mottled
appearance anyway) the corrector plate simply looks 'dull' for lack of a
better word. This is inside under artificial light. Outside in indirect
sunlight, it looks pretty good. As I have a few more hours to wait until
it's dark here, I won't be able to check it out on Mars but frankly I'm
pretty apprehensive that I have damaged the corrector plate.

One, your thoughts would be appreciated. And two, if I have to send the
scope back to Meade to have them make it all shiny and beautiful again,
any idea what they might charge? Hopefully nothing as I followed their
'recipe' for the cleaning solution!

  #2  
Old September 2nd 03, 05:12 AM
Steve
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Hard to say from your description if there's any damage, but hopefully you
didn't "rub" the corrector plate.
I very rarely clean mine, and just use compressed at an oblique angle to
gently blow off dust particles.
A slightly dirty lens is better than a scratched one, any day.

If I do have to clean it, I'll use a soln similar to what you described and
a very soft LINT FREE cloth and just drap it over the lens and very gently
pull it off from center to edge. ONLY do this after blowing off (with dry
compressed air) any contaminants.
NEVER use an air compressor for the cleaning, this air is VERY dirty with
oil and other nasties that would be very bad for the lens.
Just use canned air, and be careful at that.


Good luck.

Steve



"JD" wrote in message
...
While out viewing Mars last week, my Meade ETX-125 corrector plate got a
pretty good dose of dew over the course of the evening. I let the scope
thoroughly dry and upon inspection the next day, the corrector plate had
a somewhat mottled appearance. Nothing serious, but enough to make me
want to get it back to the pristine condition it was in when it was new.

Anyway, per Meade's instructions, I mixed a solution of distilled water
and isopropyl alcohol to make a cleaning solution. Then using a small
amount of solution and a microfiber towel, I proceeded to 'clean' the
corrector plate. It appeared that the solution was removing more than
the accumulated dust and dew spots- almost like it was removing the
coating on the plate. At this point I was committed to the task so I
proceeded to finish cleaning the entire outside surface of the corrector
plate.

Now, when it is completely dry and 'clean' (?, no more mottled
appearance anyway) the corrector plate simply looks 'dull' for lack of a
better word. This is inside under artificial light. Outside in indirect
sunlight, it looks pretty good. As I have a few more hours to wait until
it's dark here, I won't be able to check it out on Mars but frankly I'm
pretty apprehensive that I have damaged the corrector plate.

One, your thoughts would be appreciated. And two, if I have to send the
scope back to Meade to have them make it all shiny and beautiful again,
any idea what they might charge? Hopefully nothing as I followed their
'recipe' for the cleaning solution!



  #3  
Old September 3rd 03, 09:17 AM
Roger Halstead
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On Tue, 02 Sep 2003 04:12:24 GMT, "Steve" no.spam@please wrote:

Hard to say from your description if there's any damage, but hopefully you
didn't "rub" the corrector plate.


I use cotton balls soaked in the same solution.
then after cleaning I let it dry and use canned air (tm) to clean off
any lint left behind.

Roger
I very rarely clean mine, and just use compressed at an oblique angle to
gently blow off dust particles.
A slightly dirty lens is better than a scratched one, any day.


Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)
  #4  
Old September 4th 03, 06:15 AM
Ralph Hertle
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JD:

Previous posts have had a considerable amount to say about these
coatings. You might consider a keyword search.

My old Intergraph CAD CRT computer monitors have fluorite coated
screens. When viewed in a certain light the screens have a dull
purplish-pink cast to them. That was an anti-reflection coating: light
from a distant source would go into the screen and wouldn't come out.
Reflections were dimmed by say 60%.

Intergraph recommended the use of isopropyl alcohol for cleaning the
screens. Industrial KimWipes were also used due to the lack of dust and
abrasive qualities. Kleenex should not be used due to abrasion. The
isopropyl would clean off light oils and fingerprints and not touch the
coating. When there is an oil film on the screen surface it would appear
to be glossy. After 2 or 3 light applications each followed by a dry
tissue, the fluorite screen will appear properly dull. That is the
non-reflective coating working. The fluorite coating is very soft as
minerals go, and also being quite thin it can easily be worn off.

In camera optics the Fluorite coating provides an optical surface that
has a specific index of refraction. Removal of the coating may alter the
optical characteristics of the system. Whether high performance optics
have glossy fluorite coatings I cannot say, however, the camera lenses
that I've seen do appear to be glossy. If the coating roughness is
involved in the diffuse vs. specular reflection, glossy may be better,
and that is a question for the engineers.

Optical engineers may have some comment regarding the glossy or dull
coatings and suggestions for reapplying the coating. I haven't been able
to find how that is done.

My thought is that the dullness of the fluorite coating is due to the
non-reflection of certain frequencies and not to the changes of the
index of refraction or micro-surface that are involved with diffuse
reflection.

Ralph Hertle




JD wrote:
While out viewing Mars last week, my Meade ETX-125 corrector plate got a
pretty good dose of dew over the course of the evening. I let the scope
thoroughly dry and upon inspection the next day, the corrector plate had
a somewhat mottled appearance. Nothing serious, but enough to make me
want to get it back to the pristine condition it was in when it was new.

Anyway, per Meade's instructions, I mixed a solution of distilled water
and isopropyl alcohol to make a cleaning solution. Then using a small
amount of solution and a microfiber towel, I proceeded to 'clean' the
corrector plate. It appeared that the solution was removing more than
the accumulated dust and dew spots- almost like it was removing the
coating on the plate. At this point I was committed to the task so I
proceeded to finish cleaning the entire outside surface of the corrector
plate.

Now, when it is completely dry and 'clean' (?, no more mottled
appearance anyway) the corrector plate simply looks 'dull' for lack of a
better word. This is inside under artificial light. Outside in indirect
sunlight, it looks pretty good. As I have a few more hours to wait until
it's dark here, I won't be able to check it out on Mars but frankly I'm
pretty apprehensive that I have damaged the corrector plate.

One, your thoughts would be appreciated. And two, if I have to send the
scope back to Meade to have them make it all shiny and beautiful again,
any idea what they might charge? Hopefully nothing as I followed their
'recipe' for the cleaning solution!


  #5  
Old September 4th 03, 02:11 PM
Dave Phillips
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I own a Celestron Ultima 2k and have cleaned the plate once in the 4 years I
have owned this scope. The reason..some annoying smudges (fingerprints). I
used only distilled water with a squirt bottle and a hair dryer on low. A
few flushings and all was right again. I read that alcohol will leave a
residue and needs to be rinsed clean.

Just my 2 cents.


 




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