Demounting Corrector Plate for Celestron C-14

   In an attempt to 'stabilize the 'rotation' problem of the secondary on my C-14, Celestron sent me these directions.
This has nothing about eliminating the 'rotation' of the secondary, just removing the corrector plate and the primary mirror.
    More explanation of removal and cleaning the corrector plate.

 From Terry Chatterton of the Denver Astronomical society:

  Well, I guess I've been chosen for this month's D Files. My telescoping started years ago, as a result of the media hype over Comet Kohoutek.
I bought a small 60 mm refractor, which was soon in the closet. I got aperture fever from looking through a C-14.
Thanks to the help of Cathie Havens at S & S Optika, and a few payments, I bought a C-11; now well added onto and modified.
SCTs are fair telescopes but suffer a little in a few respects.
One big one is the sloppy movement of the primary mirror when focusing, so get a focuser that operates from the eyepiece. I recommend JMI as a source.
My other adjustments would make Celestron roll over in their grave. But don't worry about Celestron, they're doing fine.

Don't worry if you are not mechanically minded. If you are very careful, you can free up some of the optic pinch in SCTs.

Now comes the fun of recollimation of the system, with the hex adjustment screws.
Use a star test to get the secondary shadow in the middle of the diffraction rings.
Note that after you are finely collimated this way, your secondary and housing will rotate
to finer tune the optic, due to deviations of the secondary on its housing.

You have now relieved all stress on two optical surfaces.

Do NOT do this if you have a new scope, for I believe that it will null the warranty. If you feel nervous about working with your scope, leave it alone.
The primary is another silicon nightmare, but I haven't been brave enough to tackle it yet.

Joined: 07 Apr 2007
Posts: 827
Location: Sitting by a log fire in England.
PostPosted: 14 Aug 07 09:40
Post subject: Cleaning Optics  Reply with quote

The cleaning method for the corrector and mirrors is different - the cleaning mixture for the mirror contains Isopropyl Alcohol but not for the corrector
(this is because of the anti-reflective coating on the corrector can be damaged by alcohol).

The cleaning mixture for the Primary and Secondary Mirrors:
* 1 Part Purified Distilled Water (best to use Medical Grade which you can usually purchase from a pharmacy).
* 1 Part >98% Pure Isopropyl Alcohol (Medical Grade usually is 98/99% pure so is a good choice). On no account use "Rubbing" Alcohol or less pure alcohol
as it can contain oils which can really muck up your optics!         (Everclear works well also.)
* 1 or 2 drops of bio-degradable detergent (washing up liquid) per litre.

The cleaning mixture for the Corrector is:
* Purified Distilled Water (best to use Medical Grade which you can usually purchase from a pharmacy).
* 1 or 2 drops of bio-degradable detergent (washing up liquid) per litre.

The other supplies required are:
* Pure Cotton Wool balls (only if you can find medical grade as these are "pure").
* Lens cleaning tissues.
* Unscented tissues (I use Kleenex but just make sure they don't have any oils or other additives).
* Air "Puffer" (I NEVER use compressed air cans whether designed for cameras or otherwise - however careful you are there is always
   the risk of propellent spattering on the optics).
* Soft lens cleaning brush (as soft as you can find).
* Pure cotton gloves (I also wear latex glove underneath to prevent any skin oils getting into the cotton gloves).

Cleaning method:
1. Use the Air Puffer to blow off as much dust as possible taking care not to touch the optics with the end of the Puffer.
2. Use the soft brush to dislodge any particles which won't budge with the Air Puffer and then blow off with the Puffer.
3. Moisten (nearly soaked) a Cotton Wool Ball and gently wipe a single line from the centre to the edge of the optic using barely the weight
    of the ball to apply pressure. Throw the ball away after one stroke!
4. Depending upon how quickly any residue is drying, you then follow up with either a dry Cotton Wool Ball, Lens Tissue or normal tissue,
    to dry the optic - once again applying VERY little pressure.
5. Repeat on any stubborn areas - use a cotton bud on any particularly stubborn areas.

I carried out an additional step on the SCT optics as they were SO dirty..... I first ran the whole optic under a warn tap to dislodge much of the dirt.
I then poured some of my cleaning mixture over it to drive off the tap water which, if allowed to dry, would leave a residue or streak on the optic.

Some people believe you can use cans of compressed air specifically designed for camera lenses to clean optics - I disagree! This is based on
personal experience when, having bought the best brand I could find, and following ALL recommendations such as not shaking the can, keeping it
upright etc., it spattered propellent onto a $500 H-Alpha filter! On cleaning, it was obvious that the propellent had done permanent damage to the
filter coating. It just isn't worth the risk.

I do though now use a compressed CO2 "Duster". This lovely little device uses the small canisters of CO2 which you put in a soda syphon -
there is NO propellent so they're safe to use on optics. Just look up "CO2 Duster Kit".

There are the obvious words of caution:
* NEVER clean optics unless ABSOLUTELY necessary.
* NEVER clean optics "dry" - always use the correct mixture for the correct optic.
* Never allow cleaning solution to the edge of sealed or "layered" optics - it WILL find a way between the optic components!
* ALWAYS throw away cleaning material after a single "wipe".
* Only use verified "pure" ingredients.
* ALWAYS try a test area on the edge of the optic before starting - leave it for an hour to check if it has damaged or otherwise marked the optic.
* If in doubt, leave out the alcohol!

I suspect you may not have wanted all that detail David but, if I left anything out, someone might use the method and damage their optics!

 TomT-Starmon      Nov. 15, 2008         Enjoy.....  AstroP