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Cleaning the optics of a C8, Yes the Mirror too!

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#1 bcuddihee

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Posted 14 July 2013 - 03:58 PM

Today I decided to clean the optics of my 6 yr old C8SE. I have to say that I have been blessed with an exceptional example optically. The prevailing wisdom says to leave it alone, the views won't be that much affected, but I disagree. It seems to me with all the talk about mirror surface smoothness and resulting scatter, that a hazy, dirty mirror would just not perform as well as a clean one. I wanted that new scope look and performance and was determined to get it back! The same thing held true ...to a lesser degree with the corrector...so I started cleaning. Let me begin by saying that I used no special elixirs or formulations when doing this...simple Glass Plus and microfiber cloths. I started with the corrector that had a random dispersion of pollen specs over its surface. I sprayed a little GP on the microfiber cloth and started working from 12 o'clock to 6 o'clock, turning and changing cloths regularly. I repeated on the other side. Any mild streaking was taken care of with a clean microfiber cloth and hot breath. When I finished it was crystal clear with no streaks to be found..and I looked at it from every conceivable angle. I can't stress enough about using hot breath as a final touch of...it works!
Now onto the mirror. I figured the mirror may be a bit different due to changes in coatings etc., so after removing the corrector I tried just a small 1/4 inch arc at about the 1-3 o'clock position just to see if the haze could be removed and if the streaking would be manageable.
At first glance..I knew it would work. The difference in reflectivity and light scatter between the area cleaned and not cleaned was truly dramatic..so I went at it using the same method as for the corrector. At the end of twenty minutes the mirror looked new! I mean it..no streaks no scratches nothing but beautiful clean mirror and the reflectivity was greatly enhanced. So, for any of you that have looked at your SCT mirrors and sighed,,resigned to what it is,,there is indeed hope and a cure for dirty SCT mirrors and correctors. Looking into the front end of my scope now makes me smile because I know the optics will perform as intended.
Signed ..very happy camper! :cool:

#2 Petrus351

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Posted 15 July 2013 - 05:37 AM

I don´t think a 6 years old closed tube SCT should have its main mirror so dirty, to need cleaning; ¿outgassing maybe? I have a C8 that is 16 years old, and I have never cleaned its main mirror, but I do have cleaned the corrector, and the views are the same since the first day of use.



Greetings

#3 bcuddihee

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Posted 15 July 2013 - 07:35 AM

I do think it is an outgassing issue. There has always been a strong paint type smell inside the ota.

#4 Eddgie

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Posted 15 July 2013 - 08:00 AM

After 15 months, my EdgeHD 8" developed a very strong hazing on the correector (and maybe the secondary as well but I could not see it) and I am positive that it was some kind of outgassing.

So, I get it. Closed tube does not protect you from outgassing and in fact, traps the gas until it can condense.

Happy to hear it went well.

Modern SCT mirrors are all coated with very hard Silicone Dioxide. This material is harder than the glass below the aluminum coating and with reasonable care there shoud be no worries about cleaning it.

More importantly is that if the rear cell was removed, that the tube was not tilted with respect to the optical axis when it was re-assembled. This will give a decentering of the secondary. Make sure you check for this if you dropped the rear cell.

#5 bcuddihee

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Posted 15 July 2013 - 10:56 AM

Eddgie..fortunately I was able to do the procedure without removing the rear cell or mirror. I cant say enough about what a difference between before and after.

#6 Petrus351

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Posted 15 July 2013 - 03:37 PM

After 15 months, my EdgeHD 8" developed a very strong hazing on the correector (and maybe the secondary as well but I could not see it) and I am positive that it was some kind of outgassing.

So, I get it. Closed tube does not protect you from outgassing and in fact, traps the gas until it can condense.

Happy to hear it went well.

Modern SCT mirrors are all coated with very hard Silicone Dioxide. This material is harder than the glass below the aluminum coating and with reasonable care there shoud be no worries about cleaning it.

More importantly is that if the rear cell was removed, that the tube was not tilted with respect to the optical axis when it was re-assembled. This will give a decentering of the secondary. Make sure you check for this if you dropped the rear cell.


Of course a closed tube doesn´t protect from outgassing; that´s why I said "outgassing maybe"?






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