Corrector plate

[oshb5]

Hi all

You may know from my recent posts that i have bought a old Celestron Classic 8 in need of a good clean. Well it all stripped and in the proccess of being cleaned but i think i may have come across a bit of a hiccup In fact so much so that EUSTON i think we may have a problem I know te corrctor plate is/should be quite thick This go me thinking in that mine did not seam over thick about 3/16 or so but i also know it should be ground I put a straight edge across it today (both sides in case) and its flat Yep so looks like i have been sold a dud and at some time in its life the corrector plate has got broken or damaged and been replaced by what i can only say is normal glass This is the only explination i can see for what i have just found out.. Unless anyone can off any ray of hope

Can i ask if anyone knows the repercussions of having a fat corrector plate? Will it still work will it mess things up and do i need to try and get a propper one..

At this moment im rearly fed up but i have to think ay least every thing else is OK

Any helpful comments greatly recieved at this moment in time..

Osh

[Ender Of Days]

The corrector plate on my meade is quite curved inwards,but it is a Mak Cass,

I didn't think the Celestron would be curved ( or am I wrong ? )

by the way Whats it look like if you look through it ?

JJ..

[johninderby]

An SCT corrector plate is quite thin and the degree of curvature is so small that it would be difficult to detect using a straight edge. Indeed most people who examine one for the first time think it's just a flat glass plate.

Just wait until it's reassembled. In the highly unlikely event that it was a flat piece of glass you wouldn't be able to see anything through the telescope at all.

BTW a Mak corrector plate has a very, very large amount of curvature and is very thick.

John

[CGolder]

they should have slight shifts in the surface due to the mirror corrections and the process in which is in made, i am 90% sure the correctors on mine are thicker on the inner.

seems like someone went though a lot to be a plain glass corrector in~?? if its true you could but it back and use it still to hold the secondary or replace them with spiders... just seems improbable that someone would bother replacing it with plain glass

[John]

I took a C8 apart once for cleaning. As John says the corrector plate looks just like a flat, piece of glass. It does have a figure to it but it is very subtle. Here are some pics of a Meade SCT being taken apart:

Flocking a Schmidt-Cassegrain OTA

[oshb5]

I had the straight edge on and tried with a feeler gauge to find any differing surface points but to no avail Like has been said i will clean it and replace it and see what happens.. I also was expecting some paper shims but there was also non of them. That all said i agree it would be a right job to just replace the corrector with plain glass would it not.. My mind is now easing some what not to much though till it gets its next light I hope and all fingers and toes crossed here..

Thanks for the replies

Regards Andy

[John]

You will soon find out - if it's flat glass then I imagine the views of anything would be awful !.

[Plantins]

The corrector plates on SCT's are only thin. The corrector plates are also matched to the primary mirrors optics of each particular scope. If a corrector plate is broken at anytime the scope would need to go back to the manufacturers to make a compatible corrector, you can't just get a corrector plate off another scope.

[oshb5]

Hi

So its a waiting game now LOL well will keep you all informed. Im expecting the view to be **** to start with due to it needing collomation But If what you say is true i should see the differeance straight away correct

[yeti monster]

Hi all

.....so that EUSTON i think we may have a problem ....

[oshb5]

Well iv not cleaned it or put it back together as yet """BUT""" I was worrying to much i have had the large Shirlock Holmes magnifying glass out started a Close investigation of the corrector plate. As i had been told that no matter what there will be a serial No on it as this is needed if you remove the secondary mirror Because there is a line on the back of it that has to point to the serial number on the corrector plate.. So i started to look under good light and i eventually found the serial number its less than 1mm high and under 4mm long Wow what a weight off my mind ..

Osh