Hi all,
My 9.25 CGEM seems to have some kind of very light fogging on the inside of the corrector, It almost looks like a chemical fog more than a water fog.. I have tried a few different ways to get rid of it. This is what i have tried:
1. at the end of an observing session i rotate the OTA so it is vertical with the corrector pointing at the ground
2. 1.25" Desiccant cap used in visual back.
3. Desiccant satchels placed in the corrector dust cap
4. opened the roof of the observatory in the middle of the day and covered the telescope and mount in a white cotton sheet, and let it heat up to 25 degrees to try and evaporate the fog.
and it is still there! I have thought about removing the corrector and cleaning it using Celestrons recommended cleaning (shown below)
Celestron recommends a solution of 60% isopropyl alcohol and 40% distilled water, to which a couple of drops of liquid dish soap per quart of liquid may be added. Meade’s recommendation is similar: 1/3 isopropyl alcohol (90% or better) and 2/3 distilled water with one drop of biodegradable liquid dishwashing soap per pint of solution.
Should I remove the corrector and clean it, or should i just ignore it? its only noticeable if i shine a torch down the tube, or look at it on an angle.
Has anyone here removed a correcting lens before? if so, is it a difficult undertaking?
I understand that the corrector needs to be put back on exactly the same way it came off, and you need to count how many turns the screws take to remove, and applying the same tension as factory.
Any insight or other methods of removal would be greatly appreciated! and does this fog affect imaging?
I've never taken apart a Schmidt-Cassegrain, but I do wash the meniscus (and primary mirror) of my Maksutov-Cassegrain about once every two or three years. Over time stuff just seems to get into the tube, after all it's not a sealed system.
I take care to replace everything in the original orientation and tighten the screws to just hold things in place without rattling. I don't think the orientation matters much with my scope, though, I had put it together differently once on purpose and it didn't seem to cause any degradation to the star test images.
Yes, it's worth doing if you're worried. If there is something there, it could make it more likely to attract dewing. Removing and cleaning the corrector is not hard. You just need to be a bit systematic and careful. The formulas you've shown are good but make sure you use non-coloured detergent (one drop is good) and lots of plain, soft tissues - only one wipe with each and then discard. Get rid of any dust or grit with a blower before you start. When you take off the retaining ring, look for an index mark on the edge that shows the correct orientation relative to the primary (mine was marked with a texta), and return it to the same position afterwards.Counting screw turns sounds obsessive and unnecessary. Just make sure you don't use excessive force when fastening it.
...and try to avoid shining a torch into your optics. There will always be something there and it will only make you worry : )
Graeme is right , dont shine a torch into your optics , it will show things that dont effect the viewing , if it was my scope I would leave it alone as to effect the views it has to be really bad .
Brian.
Hi James-I had a 10" Meade S/C many years ago, and it developed a similar appearance to yours, but in my case the actual coating on the inside of the corrector plate had deteriorated. It looked just like mild condensation. My scope had to go back to Meade in USA for a complete replacement of the optics-done under warranty, but cost me a heap for freight!
Well after much umming and ahhing, and looking at the telescope today in daylight and being able to see the haze very clearly, Im going to remove the corrector and clean it. ive read close to 20 articles, and watched a few videos about the proceedure, and the general consensus is that it is not a difficult job, its just a job that requires systematic cleaning, and no rushing the job.
Ive got the shopping list ready to buy the supplies tomorrow, and i will do this while the children are at school so there will be no chance of accidental damage.
I just have this overwhelming feeling it is the cause to a lot of the fuzziness i get when viewing jupiter and other bright objects. I have eliminated every other variable, new EP's, perfect focus, dew sheild + Heating straps, and now that i have a guider (yes its my fault for the rain this time) i would assume that longer exposures are going to really show up the fuzziness! Wish me luck
Cleaning the corrector was quite easy, followed the instructions on proper cleaning proceedures, and it came out perfect!
I used close to half box of tissues, and 1/2 a roll of surgical grade cotton wool. worked a charm! and total time spent was 3 hours (2.5 hours cleaning)
im very happy with the results, excuse the photos, didnt realise how shakey the shot was but you can clearly see the haze in the first pic.
HAd a Skywatcher Maksutov once - meniscus looked perfectly clean util you shone a light on it... then you could see things, INTERNAL.
Worst of all, SW in their brilliance had written in wax pencil or Chinagraph, a number (a batch number or assembly number) on the outside surface, which they obviously removed at final build, BUT it was DEFINITELY still visible under light, and was VERY hard to eliminate. VERY!!!
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Graeme is right , dont shine a torch into your optics , it will show things that dont effect the viewing , if it was my scope I would leave it alone as to effect the views it has to be really bad .
