correcter plate clean

[alan meehan]

I have just recently been given a celestron C8 1983 orange tube scope complete to add to my collection of classic scopes i have cleaned many mirrors and glass before but never come across a correcter plate as bad as this one i have washed in warm slightly detergent water demineralised water
bintel glass cleaner isopropyl alcohol and nothing has removed the mark stain even tried liquid mould remover nope still there has need a solution anyone

[Boozlefoot]

Hydrogen Peroxide 3%, give it a minute or two to soak - maybe a few drops of ammonia in a fresh batch of the solution if this doesn't budge it.

[Rainmaker]

Are you cleaning the correct side? ;):D

[alan meehan]

Thanks guys yes iam going to give the hydrogen Peroxide and Ammonia tomorrow by all accounts that should work i hope and yes have done both sides its tough

[ausastronomer]

If you can remove the secondary and the secondary housing from the corrector plate you then have a whole heap more options available, as a lot of products might etch the metal but not harm the glass or coatings. I've never owned one of those so don't know if it separates down to just the glass corrector plate.

If you can separate the components your best option is a chlorine based pre wash soaker. You will need to leave it soak several days. Let it soak for 24 hours then rinse off any crud that has loosened and put it back in the soaker. Continually repeat the process, it will work deeper and deeper over several days as you rinse off the top layers.

The same stuff also does a really good job of cleaning glasses and other kitchen items that have become grotty. I know it sounds silly but trust me on it. I worked in hospitality for 30 years and we used specialised chlorine based soakers (Bracton Pink) to clean all the glasses, crockery and cutlery. The stronger pre wash soakers are chemically very similar to Bracton Pink, except they aren't pink.

Sards Super Soaker at Woolworths (https://www.woolworths.com.au/shop/productdetails/657182/sard-super-power-stain-remover-powder-soaker)

[astro744]

If you remove the corrector plate first mark both it and the tube and note the front (outer) side. It is likely a match to your primary/secondary combination and will give best performance in only one position.

[alan meehan]

well i have tryed everything i can lay my hands on to clean this corrector plate ,hydrogen peroxide mix with ammonia ,alcohol,bleach,acetone,vinegar
have not done the sard as yet john i will that ago .I have even let these soak for 5 days both sides before giving it a detergent wash iam stumped.Astro you only have to line up the secondary mirror centre this is done with cork shims because it is circular it does not need to go in any one position

[MortonH]

I've read many times on Cloudy Nights that the factory sets the orientation of the corrector for the best performance with the primary. There would have been marks added at the factory when the scope was originally put together but in such an old scope they may no longer be visible. Sure, it'll work in any position but there's an optimal one.

[alan meehan]

you are probably right there maybe marks at some stage in 1983 but not any now.,i did mark the corrector plate but with all the washing and soaking its gone to ,before i get it back together ive got to get this clean iam now soaking it i baking soda and vinegar if it does not come clean it will not matter what position it is in,it will become a static display

[glend]

Alan, it almost looks as if it was sandblasted at some point. It the damage is something like that no amount of solution bathing is going to fix it. If your resigned to it being a static display item, why not try a car polishing compound? Get a bit of the very fine paint polishing compound and try one spot. It will likely not removed the glass in the way of a glass polish, but could certainly remove clouded coating. Good luck.

[GUS.K]

Not sure if you've tried CLR cleaner (available at Bunnings). I used it to remove some outgassing stains that wouldn't come out with anything else. Also used by others to remove residue on the Lunt solar BG filter in their blocking filters.

[alan meehan]

Thanks Glen and Gus but i have tried a bit of fine cutting compound and polish combo but it did not remove it will try CLR Cleaner this is how it looks after 2 weeks of cleaning and soaking inc baking soda and vinegar overnight

[Peter Ward]

I have toured the the Celestron factory in Torrance a few times and know they
both index and centre the corrector plate. You really needed to scribe-mark the edge of the corrector during the removal process...but what's done is done.

At this stage you might as well pull the secondary off the corrector and try your hand at applying a pitch lap and polishing rouge. I suspect the AR coatings have perished anyway, so nothing to lose by removing them.

Polishing may affect the catenery curve of the corrector, but meh... at least it will look pretty again.

[alan meehan]

Thanks Peter you are correct about the positioning and i did mark it but during the intense washing its the only thing that washed off it does sit well in with my other classic scopes just leave the cover on