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Converting C8 with broken corrector plate to Cassegrain/Ritchey-Chretien

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45 replies to this topic

#26 Don W

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Posted 06 July 2021 - 11:56 AM

I can't see any logic in buy a 2nd hand C8 OTA just to take out the corrector and put it your broken scope. That corrector is more than likely matched to the primary in that OTA. It would be best just to use the entire 2nd hand OTA.



#27 jgraham

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Posted 06 July 2021 - 12:19 PM

I once received a used SCT whose corrector was shattered during shipping. I tinkered with the idea of converting it into a lensless Schmidt camera, but the carrier kept the scope as part of the insurance settlement. T'would have been an interesting project. (I previously converted 3 Celestron Schmidt cameras from film to digital.)

Briefly; place a small digital camera at the prime focus and a 4" aperture mask at the radius of curvature.

Food for thought, dine carefully. :)
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#28 Jaimo!

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Posted 07 July 2021 - 11:19 AM

Food for thought, dine carefully. smile.gif

funnypost.gif



#29 teashea

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Posted 09 July 2021 - 07:55 PM

It was a worthwhile question.  I don't remember ever seeing a more unanimous set of responses to a question on CN.  



#30 mhammady

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Posted 30 August 2021 - 01:21 AM

Hello

Wanted to update my status: converting the C8 didn’t work at all. As everyone mentioned above, the corrector plate is needed with the existing set of mirrors.

I was lick enough to get a used 8” corrector plate from a scrap old Meade scope for about $150 with shipping, and I needed to 3D print a sold ring to work as adapter to compensate for the inner circle cut as Meade was 0.2 inches larger in diameter. After doing full calibration using my hotech laser collimator for SCT, it works as new…

I’m very happy with this results…
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#31 dweller25

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Posted 30 August 2021 - 02:10 AM

A Meade corrector on a Celestron, Well done waytogo.gif


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#32 Lighthound

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Posted 30 August 2021 - 09:12 AM

"Celemeade"


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#33 teashea

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Posted 30 August 2021 - 10:39 PM

Hello

Wanted to update my status: converting the C8 didn’t work at all. As everyone mentioned above, the corrector plate is needed with the existing set of mirrors.

I was lick enough to get a used 8” corrector plate from a scrap old Meade scope for about $150 with shipping, and I needed to 3D print a sold ring to work as adapter to compensate for the inner circle cut as Meade was 0.2 inches larger in diameter. After doing full calibration using my hotech laser collimator for SCT, it works as new…

I’m very happy with this results…

excellent



#34 dcaponeii

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Posted 02 September 2021 - 05:00 PM

"Celemeade"

I think it's Meadatron


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#35 CeeKay

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Posted 02 September 2021 - 07:49 PM

How about that... a "Metron"!


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#36 brentknight

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Posted 02 September 2021 - 08:44 PM

How bad was the broken original corrector?



#37 Garyth64

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Posted 02 September 2021 - 09:40 PM

Which secondary did you use?

 

Have you looked thru it?


Edited by Garyth64, 02 September 2021 - 09:41 PM.


#38 jgraham

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Posted 03 September 2021 - 07:08 AM

That's so cool. Well done!

Enjoy your unique scope!

#39 mhammady

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Posted 06 September 2021 - 12:42 PM

Which secondary did you use?

 

Have you looked thru it?

I used the one that came originally with the scope. I only replaced C8 corrector plate with Meade 8" corrector plate.


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#40 mhammady

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Posted 06 September 2021 - 12:43 PM

How bad was the broken original corrector?

It was 3 pieces :(



#41 Garyth64

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Posted 06 September 2021 - 04:09 PM

I used the one that came originally with the scope. I only replaced C8 corrector plate with Meade 8" corrector plate.

So have you looked thru it yet?

 

It just seems that between the Meade and the Celestron, the secondaries have the same exact radius of curvature? and can be placed the same distance from the primary? and that is of course if the primaries have the same focal length too.  Aaand, the correctors had the same amount of correction needed for the system?   Hmmm  It may fit, but does it actually work?  Too many variables.


Edited by Garyth64, 06 September 2021 - 04:12 PM.


#42 brentknight

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Posted 06 September 2021 - 04:50 PM

It was 3 pieces frown.gif

Ahhh.  I can see that would be bad.  I knocked my C8 off a shelf onto carpet and it put a couple minor dents in the tube and a single straight crack from the edge to the secondary.  Honestly, I see no ill effects with a camera or visually, but it does make me a little ill whenever I look at the glass...



#43 mhammady

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Posted 06 September 2021 - 05:06 PM

So have you looked thru it yet?

 

It just seems that between the Meade and the Celestron, the secondaries have the same exact radius of curvature? and can be placed the same distance from the primary? and that is of course if the primaries have the same focal length too.  Aaand, the correctors had the same amount of correction needed for the system?   Hmmm  It may fit, but does it actually work?  Too many variables.

I did after collimation. I had to align the 2ry to the optical axis, and the eyepiece to the same, then I performed the regular collimation for the 2ry mirror. I had a look after that and the stars were crisp clear. I really don't know much about curvatures, but I tried to use them without the corrector plate but as mentioned earlier, an only a small (very small) circle that has a visible image, and the rest is foggy, or IDK maybe out of focus. Even a full moon was not visible. As soon as I put the corrector plate from Meade and did my calibration and collimation, its crisp clear again.


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#44 jpengstrom

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Posted 06 September 2021 - 06:32 PM

Glad to you know you got it sorted out and got your scope working again!  And also nice to know that a Meade 8" corrector works on a C8.



#45 Garyth64

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Posted 08 September 2021 - 07:29 AM

I'm sure we all would like to see a picture.

 

When you tried it before without the corrector plate, what was holding the secondary in place?


Edited by Garyth64, 08 September 2021 - 07:35 AM.


#46 mhammady

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Posted 23 September 2021 - 07:26 AM

I'm sure we all would like to see a picture.

When you tried it before without the corrector plate, what was holding the secondary in place?


I designed a holder for the secondary mirror and printed it

https://a360.co/2XKHyDF

70f09fa19e8c2949bbca0c1ccd220267.jpg


For the picture, currently I don’t have mount for the c8 but I plan to buy used one for it as my other 2 mounts are already in use…


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