Corrector Plate Smudges

[Guest CodnorPaul]

I was checking over my C8 this morning after installing bobs knobs and noticed that the corrector plate was filthy and had something dried onto it - I must have not had the dew control on enough earlier in the week and had some moisture when I put it away.  I decided I had to give it a clean it was that bad so went through the usual process to clean the outside - came up a treat.  But when I look through the corrector at an angle there are now 2 very small, and faint smudges on the inside of the corrector, which I am sure were not there before.  They are only about 1/2 cm or so.

 

So my questions are:

1. Is this possibly due to dew, and it has somehow got inside the OTA?
   
2. Could this turn fungal and therefore needs to be removed?  I really don't fancy removing the corrector plate
   

 

When I look straight through the corrector at the mirror I cannot see them, it is only when viewed at an angle, so I don't envisage they will affect the viewing at this point.  If it needs a clean on the inside is anyone sufficiently confident to help me with this?

[dawson]

Can you image them with a camera or phone looking at the corrector plate at an angle for us?

 

I've had mine of several times, and it is scarey, but largely easy to do and hasn't yet upset my collimation.... touch wood.

 

Did you have the scope from new? If not, it might be that someone else had the corrector plate off and left a mark on the inside? It could be fungus, has the scope been left in a dampish place for long periods of time?

 

Moisture can always get inside as it's not a sealed system.

 

If it's just a grease mark, I'd be tempted to leave well alone, don't rush to take the corrector plate off unless you really need to. If it's fungus, then speak to someone like PhilJay who is the refractor king and probably what is good fro refractors in this situation will be good for SCTs/Maks.

 

[if you do take it off, mark which screw holes on the OTA go with which screw holes in the corrector plate to minimise the risk of you putting it back on in a different position which may knock out the collimation]

 

James

[Guest CodnorPaul]

I am not sure they would show up in a picture James - they are not that obvious to see and looking on other sites at picture of correctors with people who say they are really filthy they don't show up well.

 

No not from new - but I am sure they weren't there before, could of course be wrong but I don't think they were.  And I never leave it damp - always put the front cover on with the dew control still on, leave the front cover in a dry place when observing, check the corrector visually before putting the cover on, and normally get paranoid and check the day after using that it is dry.  It is then stored in a foam lined, tightly shut, storage box inside the house so does not get cold/damp.

[dawson]

Look at the screws which hold the corrector plate on, is there any sign they might have been unscrewed at any time?

 

I tend to leave my scope open a bit when not in use to allow air to circulate.

 

I think your corrector plate is just one sheet of glass, so the marks are either on the outside (and you say they are not) or the inside, so they should be removable one way or another. It's not like a refractor where there may be two or more lenses touching each other where fungus can grown between them.

 

You need to show someone clever. Drop philjay a message if he doesn't respond to this thread.

 

But don't panic, it sounds resolvable!

 

James

[Guest CodnorPaul]

Thanks James - I wont panic at this point.  They don't look wet now, and don't really look fungal, and don't have the signs of being a greasy fingerprint, so will probably just keep an eye on them and make sure they don't get bigger or anything.  Then hopefully next meet they wont have changed and I will ask someone more knowledgeable then me to have a look.

 

As I say they are faint and looking through the corrector head on are invisible so if it was anything to worry about I think they would probably show up more.  It is of course possible they have always been there but I have only just noticed them.

 

And no signs of the corrector being off I don't believe.

 

And smudges is probably the wrong word for the title - they are just small marks

Edited October 27, 2013 by CodnorPaul

[philjay]

You can get away with alot on a sct corrector, my old c11 was embarrassing before i eventually cleaned it. For dew to have formed inside it woul have to have been seriously wet and you would have had to expose the insides of the scope to the conditions for a very long time. So if you are storing the scope damp or in a damp environment then it may be but for most folks who keep the scopes indoors i shouldnt think it would be dew.

The marks may well have been on before, its not uncomon to have marks on the inside of correctors on used scopes. Think long and hard before removing the corrector, it can be done and doing it methodically it should be relatively straightforward, but breaking into any scope needs consideration before jumping in

[Guest CodnorPaul]

Thanks Phil - it definitely wasn't that wet inside or out when it went away.  I always make sure it is dry when putting it away, and the outside of the corrector may have even not been down to dew as there was no sign of moisture when I found it, possibly just a contaminant from the conditions.  I also don't leave an EP out or the diagonal cover off for long so there cant have been that much moisture getting in.

 

It is very possible they were there before and went unnoticed.  Am going to leave the corrector well alone for now.

[Tweedledee]

Such horrendous image destroying smudges are really going to render your scope next to useless!! I'll take it off your hands for £50 scrap value

In reality though, you have described two smudges about half a centimetre in size that are difficult to see or even photograph in daylight. In other words you have "something or nothing" partially obscuring less than 1/800th of your scope aperture that may or may not degrade your viewing or imaging pleasure by a similar proportion. I wish my schmidt newt corrector was that good, but it never fails to provide that wow factor.

Enjoy the views

[Guest CodnorPaul]

Ha ha - fair point well made Peter!

[red dwalf]

hi Paul,

i`ve cleaned my corrector plate once, having done alot of google searching on the matter, one website i can`t find at the moment shows a 5 year old kid taking a sct apart and putting it back together so i thought i would have a go if a little kid can do it so can i, my corrector had what looked like some thing growing on the inside of the plate that shouldn`t be there and i was alittle worried about it, so firstly i marked everything with a little bit of grey tape so i could put everything back together in the same position then dismantled the front, on the 6 inch sct you can just remove the screws on the outside ring and the lot comes off but on the 8 inch ones they have little nuts that when unscrewed fall off and roll around in the inside middle of the scope and are impossiable to put back, so you have to take the front off, it`s really not that bad a job, i did it in about an hour, just remember to mark everything, after you have removed the outer ring but alittle tape, not too sticky on the corrector plate, so it also goes back in the same position, you don`t need alot just the smallist bit, some of the corrector goes under the outer front ring and rubber gasket anyway.

when fully removed i cleaned the inside with Baader wonder fluid and a micro cloth that comes with it, this stuff is great and helps stop fungal growth also, dries without smears also and you only need alittle bit, once cleaned it looked like new and i was very happy with the result, whatever was on the inside of the corrector came off easily and no damage was done but it didn`t look nice at the time, only the smallist of bits but i could see it.

when the corrector was re fitted i then cleaned the front,

here is a picture of the tape i used to mark the position of the corrector front ring and the front of the scope.

[Guest Tweedledum]

Another vote for Baader Wonder fluid, great on the corrector but not to be used on mirrored surfaces. Had dog hair and all sorts on the inside of my 10" sct befoe cleaning.

 

if you do get the urge to remove watch out for small pieces of packing that may be there, anything from cork to cardboard. Before you remove the corrector always mark the tube and corrector in three places (or above with tape) with a bit of tipp ex or similar. IT MUST GO BACK IN THE SAME POSITION IT CAME FROM.....But in reality it is a good afternoons task when the weather is pants!!!!!

[red dwalf]

Might be worth thinking of flocking the inside of the scope Paul if you do decide to take the corrector plate off, that's my next project after the obsy is fully finished which at this rate might be a while off LO.L.

[dawson]

I think flocking an sct/mak would be really tricky, with the tube in the middle of the scope and a sensitive mirror the other end. I'm not convinced the benefits would outweigh the risks for me. Flocking the newtonian was a walk in the park, but an sct/mak would be a tricky job.

James