C9.25 corrector plate removal for cleaning

[Bellyeye]

A couple of years ago I bought a second hand C9.25. Not sure how I can tell the age of the model but it is grey with orange writing. I use this scope for visual whilst imaging with my refractor & guidescope. Whilst it has always given pleasing views, especially of planets, the image lacks contrast and is a bit soft. I've fitted Bobs Knobs to it but as yet have not properly collimated it.

However I've recently bought a Meade f6.3 reducer with a view to having a go at imaging using an off axis guider and the C9.25.

The problem is this.

The previous owner of this scope had stored it 'objective down'. The primary mirror is in pristine condition but the same can't be said for the rear of the corrector. It's covered in dust and has what look like grease or oil spots. These look like something has dropped onto the glass and spread outwards. I dread to think what the secondary is going to look like.

I've decided to take the corrector off and clean it. I will flock the interior also - might as well while I'm in there!

I'll take some pictures as I go along and post them here.

Wish me luck.

www.flickr.com/photos/greggylike/sets/72157632571499958

John

[kirkster501]

Good luck mate, very interested to see how you get on, what materials you use, the technique etc.

Reds, Steve

Sent from my iPhone using Tapatalk

[rowan46]

don't forget to mark your tube and corrector so that they go back in the same orientation

[Bellyeye]

Yes I've seen different ways of marking up the corrector against the tube - I think the method I prefer is 3 small pieces of different coloured electrical tape from the corrector to the housing cut with a razor blade.

Got that from here

[Space Dragon]

This isn't unheard of and it's simply the grease that's applied to the moving parts of the mirror dripping down onto the corrector, probably due to warm temperatures.

It's recommended to store the scope at 45º upwards if possible to avoid this, it also take strain of the weight of the mirror better in this orientation.

Good luck with it and as mentioned, make sure it goes back as it came off. I'm sure you're already aware.

[billhinge]

I had a C11 that I left outside a couple of days, when I looked at it again it was covered in condensation on the inside and made a mess on the inside of the corrector, took a week to dry out

I decided to give it a clean and flock, it isn't such a big deal provided you are methodical

I found distilled water works better than 100% pure methanol in terms of cleaner - baader fluid is useful balance

You 'may' need to collimate again. note the the positioning of the corrector, there is a couple of mm play between the corrector and the inside of the tube

providing you are careful though it shouldn't be too much of an issue

By the way, suggest you look at protostar flock from lyra optical

[earth titan]

I did mine last year cos it had water streaks on the corrector plate, and it's no biggy. Cleaned with Baader Wonder.

For flock, I used Wilco flocking paper and it's fine.

I used scotch tape and very fine pencil to mark the original location and while doing it, fitted Bobs Knobs.

Before you take it apart, if you have a laser collimator, fit it in the end, lock it in place and mark the spot where the 'dot' hits. When you fit everything back together, providing you haven't moved the collimator, the dot should be more or less in the same place. Just gives a little comfort that it all went back together ok.

Just don't drop the corrector plate!!

Typed by me on my fone, using fumms... Excuse eny speling errurs.

[Bellyeye]

Thanks for that folks - I feel a little less nervous about tacking the job now.

I've got the Wonder Fluid and the flock is on order. I'll make a start after work :-)

[tingting44]

how have you got on mate? hopefully all good

[Uplooker]

Hi John,

You'll be fine. As others have said, just make sure you have marked the position of the corrector in relation to the tube. A lot of what people will tell you about removing (or not, as the case maybe) the corrector from a Mak or SCT make it seem like something that should never be attempted, other than Celestron or Meade Engineers.

I cleaned the corrector of my 2nd hand SCT with no issues. Just take the normal precautions for cleaning optics - cleaniness of work area, removal of grit / debris with a bulb blower etc.

When you come to remove the corrector you will be surprised how "loose" the screws are that hold the corrector retaining ring in place, remember this when you come to reattach the corrector as you do not want to put undue stress on the glass.

Once you have completed the job you will wonder what all the fuss was about.

Ian

[alan potts]

Good Luck, John. I keep meaning to clean mine.

Alan.

[Mondlicht13]

Hi John. I would be interested to hear how you got on with this job

Just in case I ever have to remove mine for cleaning. The way the weather is going it will be mainly to get the cobwebs off it !!!!!!!!!! :clouds1:

Cheers neighbour