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How to remove corrector plate - Orange Tube C5

Catadioptric SCT Celestron
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#1 btheo204

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Posted 23 October 2021 - 02:42 PM

Hey everyone, I recently picked up a 70?s orange tube C5. However, the corrector plate is a little cloudy/smudgy. I've already cleaned the outside of the corrector plate which helped, but a lot of it resides on the inside, but I have no idea how to take off the plate to clean the inside.

 

The cloudiness is only visible with a direct light shining on it, it looks fine when unlit.

 

I've used the telescope and it's pretty sharp and works well, I'm not sure how much this cloudiness affects the views, but I feel like it's a good idea to clean anyways.

 

It doesn't seem to have the screws on the side of the tube to take off the corrector as some others do. Behind the corrector are threads that seem to maybe hold it on?

 

If anyone knows how to take the corrector off, help would be greatly appreciated!

 

I'll try to attach pictures below

Attached Thumbnails

  • IMG-3098-min (2).jpg
  • IMG-3094 (1) (1).jpg

Edited by btheo204, 23 October 2021 - 02:54 PM.

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#2 macdonjh

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Posted 23 October 2021 - 03:54 PM

If your view is clear and sharp, perhaps leave well enough alone?  

 

I wouldn't be able to, either...

 

It looks like there are two small holes in the retaining ring, 180o apart.  I wonder if your retaining ring is threaded into the front casting and you need a larger spanner to unthread it?  I think you should wait for someone who's taken a small Celestron apart.  I can help with anything C8 and larger.


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#3 maroubra_boy

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Posted 23 October 2021 - 04:34 PM

Removing the corrector is not possible with this scope unless you have the tool to unwind the retention ring.

Instead you can remove the whole front cell from the tube - there are a few screws around the outside of the cell to remove. Then carefully tease out the cell from the tube. You will be able to access the inside surface of the corrector this way.

The cell may be a bit stubborn to pull out. This would be because of the many years of use will have seen dew be drawn in through the seam dragging in dirt and crap and a bit of corrosion. Take your time. A bit of isopropyl alcohol around the seam will help soften some of the gunk. Use wood wedges to gently prise out the cell if it needs a bit of physical persuasion. It will have 50 odd years of sitting there - it will need some care to remove.

Alex.
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#4 macdonjh

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Posted 23 October 2021 - 04:54 PM

Removing the corrector is not possible with this scope unless you have the tool to unwind the retention ring.

Instead you can remove the whole front cell from the tube - there are a few screws around the outside of the cell to remove. Then carefully tease out the cell from the tube. You will be able to access the inside surface of the corrector this way.

The cell may be a bit stubborn to pull out. This would be because of the many years of use will have seen dew be drawn in through the seam dragging in dirt and crap and a bit of corrosion. Take your time. A bit of isopropyl alcohol around the seam will help soften some of the gunk. Use wood wedges to gently prise out the cell if it needs a bit of physical persuasion. It will have 50 odd years of sitting there - it will need some care to remove.

Alex.

The screws holding the front casting on a C5 don't have nuts on the inside of the OTA?  They did on my C11, so I had to remove the retaining ring first, so I could hold the nuts to prevent them from spinning while I removed the screws.

 

Given the different retaining ring design it doesn't surprise me there are other design differences between a C5 and Celestron's larger scopes.


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#5 maroubra_boy

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Posted 23 October 2021 - 06:43 PM

Hmmmm,good point I hadn't thought of. I was thinking of other cell designs that wind back into the cell. Can these nuts bee seen through corrector?

#6 maroubra_boy

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Posted 23 October 2021 - 06:46 PM

Ok, I found an older CN thread discussing this very thing & the front cell was removed in the way I described:

https://www.cloudyni...orrector-plate/

It also discuses the many variants.

Alex.

Edited by maroubra_boy, 23 October 2021 - 06:48 PM.

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#7 btheo204

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Posted 24 October 2021 - 11:03 AM

Removing the corrector is not possible with this scope unless you have the tool to unwind the retention ring.

Instead you can remove the whole front cell from the tube - there are a few screws around the outside of the cell to remove. Then carefully tease out the cell from the tube. You will be able to access the inside surface of the corrector this way.

The cell may be a bit stubborn to pull out. This would be because of the many years of use will have seen dew be drawn in through the seam dragging in dirt and crap and a bit of corrosion. Take your time. A bit of isopropyl alcohol around the seam will help soften some of the gunk. Use wood wedges to gently prise out the cell if it needs a bit of physical persuasion. It will have 50 odd years of sitting there - it will need some care to remove.

Alex.

It doesn't seem to have the screws on the outside of the cell that you mentioned, I looked at the other similar thread and saw the screws that you mentioned on another persons telescope, it seems that I dont have them



#8 davidmcgo

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Posted 24 October 2021 - 01:45 PM

You can typically get the retaining ring to unscrew using a round toothpick cut in half such that the un tapered middle section is in the spanner hole.  Counterclockwise rotation as you face it will unscrew it.  Make sure the scope is pointed upwards while you do this.  Then note any cork shims around the corrector and use the pointy end of a toothpick to lift them out and hopefully the corrector isn’t stuck to the gasket behind it.  If it is, just let some isopropyl alcohol wick behind it (sparing amounts).

 

The ring should not be really tight, so the hand force on the toothpicks is about right when tightening after cleaning.

 

Dave


Edited by davidmcgo, 24 October 2021 - 01:51 PM.


#9 JMP

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Posted 24 October 2021 - 06:28 PM

I made a spanner tool for my C5. I used a strip of plywood and two drill bits, the drill bits were chosen to match the holes in the retaining ring. I measured and drilled the holes in the plywood and pushed the bits into the wood so that I had two "pins" that fit the holes.

With a little care you can make your own tool. Good luck!

Edited by JMP, 24 October 2021 - 06:31 PM.



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