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Are these cleaning marks that can be removed or is the coating damaged on the corrector plate?

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#1 Sofia52

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Posted 12 June 2022 - 07:27 PM

So I've been having a blast with the C8 I purchased recently (it's from 1973). Today I decided I would try some solar viewing. Well that didn't get very far because the filter i have was awfully scratched so I'll need to get another one. Anyway. When i happened to look at the corrector plate in the sun i saw the marks pictured. I didn't see them in the room when I purchased it. And they don't seem to affect night viewing. It's just odd and i was hoping someone with more knowledge than I would know what it is. Thank you for your time.

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  • celestron_c8_corrector_plate_damage__by_sand_the_kitty_df77n8w-fullview.jpg

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#2 oldmanastro

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Posted 12 June 2022 - 09:11 PM

They look like streaks left over from cleaning and they can be carefully cleaned out but if the views are ok just continue to use this nice classic C8 until that corrector gets really dirty. 


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#3 apfever

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Posted 12 June 2022 - 09:39 PM

I'll second Guido. Those sure look like cleaning marks in distinct individual wipes. The ones at the 7 O' Clock position close to the secondary even have the dot and dash charcteristics of wipe after it dries.  They should not be a concern that will affect the glass so take your time to get everything set up and ready to clean it if you want to proceed. Double check your intended proceedure.


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#4 LukaszLu

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Posted 14 June 2022 - 05:32 PM

This is the trap of seeing optics in strong, direct light. Even if you clean it as thoroughly as possible - seeing it in such a light is always a risk of a heart attack. Some manufacturers write directly in their manuals that you should not shine in the optics in this way because traces appear that have no practical significance for its operation.


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#5 sdedalus83

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Posted 14 June 2022 - 06:02 PM

I have a newer C5 which initially looked like frosted glass. There was some sort of oily residue on both sides of the corrector but not on the mirrors. I’m guessing someone tried to clean it with something weird. It cleaned up very nicely, with only a couple of small coating blemishes.



#6 Kokatha man

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Posted 14 June 2022 - 07:38 PM

...they're cleaning marks & it is unsettling to look at glass in strong sunlight! lol.gif

 

Although I'm unsure how reliable the old maxim is but whenever I clean my C14's corrector (more often than most would btw) I always wash from the inside out using radial strokes - not the apparently circular (or random) strokes obviously used here. wink.gif

 

A home recipe similar to the "Dr Clay's" formula has served me well over the years for cleaning, sluicing with distilled water from a simple spray bottle - but I have a neoprene seal inserted under the corrector's retaining ring to prevent water ingress.

 

My regular cleaning obsession is the result of constant pursuit of hi-res planetary imaging where I take the scope to a lot of dusty places, but as said you can get away with a pretty filthy corrector without much of an issue! wink.gif


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#7 oldmanastro

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Posted 14 June 2022 - 10:34 PM

This is the trap of seeing optics in strong, direct light. Even if you clean it as thoroughly as possible - seeing it in such a light is always a risk of a heart attack. Some manufacturers write directly in their manuals that you should not shine in the optics in this way because traces appear that have no practical significance for its operation.

This reminded me of a telescope manual that specifically instructed the owner not to do "the flashlight test" on the optics. In other words, leave well enough alone until the optics get really dirty. A few streaks from a previous cleaning will not have a significant effect on the optics.


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#8 Sofia52

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Posted 16 June 2022 - 03:56 AM

Another question for those that might know. Is the corrector plate one piece of glass or is it made of layers that can delaminate? like when the cement fails on a camera lens and you get balsam separation. I might be over thinking this i should just collimate the scope and have fun Thanks again for your time. 



#9 ccwemyss

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Posted 16 June 2022 - 05:11 AM

It’s a single piece of glass, about as thick as a window pane. If it hasn’t become stuck to the gasket, it’s easy to remove and clean. But you should read up on the process. It’s important to retain the alignment and there are spacers around the edge that need to be put back in their places. 
 

Chip W.


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#10 Sofia52

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Posted 16 June 2022 - 06:59 PM

It’s a single piece of glass, about as thick as a window pane. If it hasn’t become stuck to the gasket, it’s easy to remove and clean. But you should read up on the process. It’s important to retain the alignment and there are spacers around the edge that need to be put back in their places. 
 

Chip W.

Sweet. Thanks for the info. I'll be sure to mark and photograph everything before I remove it so it goes back in the same place Now all I need to do is collimate the scope, get a new sun filter and it should be ready



#11 Kokatha man

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Posted 16 June 2022 - 08:13 PM

Depending upon the age of your scope you'll have cardboard strips to centre it, or in modern ones nylon-tipped spigots that can be adjusted with a small hex-key. (only if found to be necessary - unusual)

 

Look for a watermark embedded in the corrector glass along the periphery - you might find several markers but on later models there is also a mark on the lip inside the ota for you to register this with against the watermark on the glass...if you are unable to discover these 2 sets of markings make some yourself to put it back the same as it was before taking apart - but do it with an indelible marker! lol.gif

 

Although whole reams of advice have been posted on the necessity to accurately align the orientation of the corrector wrt the primary, I have (inadvertently) found that there is obviously a lot of latitude in this at times* although I always advise folks to stick with the alignment marks - this at least is my experience with a US made C11 & a Chinese C14.

 

*I can demonstrate very high-resolution images of planets where the rotation of the C14's corrector was out over 3inches/75mm from the markings due to mistakenly using another watermark on the corrector after re-assembling quite a few years back..! lol.gif

 


Edited by Kokatha man, 16 June 2022 - 08:17 PM.

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#12 RichA

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Posted 17 June 2022 - 02:38 AM

Sweet. Thanks for the info. I'll be sure to mark and photograph everything before I remove it so it goes back in the same place Now all I need to do is collimate the scope, get a new sun filter and it should be ready

When you replace the retaining ring screws, they don't need to be very tight.  Not loose, but not torqued.  Use the automotive technique, tighten the screws opposite (across the diameter of the corrector)  from each other.


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#13 Sofia52

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Posted 18 June 2022 - 01:36 PM

Will do. Since I learned to change a tire I've been doing the opposite fastener method for everything, unless a manual specifically says otherwise (which I've only seen once in something that the case compressed a spring and you had to tighten the side with the spring first so the other side could even close.)

RichA, on 17 Jun 2022 - 12:38 AM, said:

When you replace the retaining ring screws, they don't need to be very tight. Not loose, but not torqued. Use the automotive technique, tighten the screws opposite (across the diameter of the corrector) from each other.



#14 deSitter

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Posted 18 June 2022 - 02:03 PM

Why are you using an 8" telescope on the Sun?? :)

 

That's nothing, get some Zeiss fluid and 91% IPA and away it goes.

 

-drl


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#15 sunrag

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Posted 18 June 2022 - 02:13 PM

I have found that all cleaning fluids and store bought distilled water leave streaks. So for the final step, i hold the glass over a steaming cup of water. Then i wipe the condensation with tissue. This seems to leave very few streaks.


Edited by sunrag, 18 June 2022 - 02:14 PM.

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#16 Sofia52

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Posted 18 June 2022 - 02:18 PM

Why are you using an 8" telescope on the Sun?? smile.gif

 

That's nothing, get some Zeiss fluid and 91% IPA and away it goes.

 

-drl

It came with a solar filter so I thought. Why not?  And thanks for the info.  


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#17 LukaszLu

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Posted 19 June 2022 - 10:38 AM

I have found that all cleaning fluids and store bought distilled water leave streaks. So for the final step, i hold the glass over a steaming cup of water. Then i wipe the condensation with tissue. This seems to leave very few streaks.

Some (including me ...) are not patient enough and limit themselves to breathing :-)


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