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Old 19-08-2018, 01:24 AM
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netwolf
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C14 Dovetail mounting

Hi All,


On the C14 my friends and I are restoring we found that the OTA seems to maybe be missing something to mount the Losmandy dovetail bar radius blocks. There are holes at the back with the right threads but at the front the holes have caps in them but dont seem to have any threads, and the losmandy supplied screws to small for the holes. A C11 my friend also has from the same time period seems to have a small metal plate on the inside of the OTA into which the two screws from the radius blocks screw in from the outside. But there is no such plate on the C14.

See attached photo of C11. The little plate is held in place by the middle screw. On the C14 there is just the middle screw with a nut but no plate.

Has anyone else found this with there C14? This is a 90's C14 and may have been fork mounted initially. But when we got it, it was in rings on a Pentax Mount. We would rather use the Losmandy plate, but seems we may have to make a metal plate and add it in. Just wanting to see what others have got and or done to resolve.

Thanks in Advance.
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  #2  
Old 19-08-2018, 10:58 PM
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g__day (Matthew)
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A left field thought - with a drill you could just drill two new holes and then with the right size and thread pitch tool just thread these two holes - which might be a sturdier solution?
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Old 20-08-2018, 07:16 AM
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Sunfish (Ray)
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When adding a Losmandy full length vixen style dovetail camera mount to my 1990 c8 I found two screw holes at the back of one thread on the scope and one at the front of another thread.

The solution was to make a plate to add on with the correct holes. I made this by heating up a 20 x 5mm bar of aluminium 75 mm long clamped to a heavy 200mm diameter aluminium plate . I formed it by hitting it with a wooden mallet while hot and spraying black. Not very elegant but far cheaper than radius blocks.

Can you bolt on radius blocks using the existing holes or add an external (or internal) threaded plate as I did.?

The other point is that the rear cell of a 1990 Celestron sct is designed to support the entire weight of the Ota and they can be supported on one camera tripod bracket . The front cell may not be so robust and so drilling or tapping it for screws without reinforcing risks deformation of the corrector support.

Last edited by Sunfish; 20-08-2018 at 08:11 AM. Reason: Adding point
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Old 20-08-2018, 08:23 AM
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Thanks Matt/Ray, we the holes are already there which line up with the back holes so did not want to drill anything new. The back holes have the right size thread which match the Losmandy radius block 3/16th UNC screws. The front holes that line up with these are covered with caps and the center one has a screw with nut on the inside. The cap covered holes dont have any threads and are bigger than the screws supplied.

Ray we are thinking of doing something similar to what you proposed but on the inside of the OTA. To make it similar to the C11 in the photo I attached above. My friend Peter has got some 3mm steel plate which he has bent to the the same radius as the Radial blocks from Losmandy. We have to remove the corrector again anyway to try the Bintel/Dr Clay cleaning solutions. So when we do that we will add this plate on the inside and it will be held in place with the central screw (replaced with longer one) and a nut. On the sides we plan to drill and tap 3/16 UNC to line up wiht the existing capped holes. Given this is a older C14 and these are supposed to be a bit heavier than the more modern ones, it would be better I think to have the screws held by something a bit more solid inside than just the OTA body. At the back is not an issue as the holes are in the thicker back plate of the OTA.

What I wanted to see was if anyone could take photos similar to mine of the C11 of there C14 to show what the setup is on the modern ones are even ones from the 90's. As I know there was a CG-14 setup sold by Celestron with Losmandy dovetail and mount.
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Old 20-08-2018, 11:09 AM
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Sunfish (Ray)
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Adding the plate on the inside would save making two as I did.

The c8 super Polaris eq mount short dovetail was mounted on the rear cell only in advertising photos. The front screw was for the weight bar or handle on either side.

Perhaps the 1990 C14 was never originally mounted this way due to its size and predates long dovetails. I have seen photos of An orange C14 mounted on a long dovetail to suit a newer mount.
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Old 22-08-2018, 08:59 PM
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trek1701 (Mark)
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Hi Fahim

Not quite sure if this is what you're after, but here's a picture of my late 70's
C14 corrector.

Regards Mark
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Old 22-08-2018, 10:47 PM
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Thx Mark ok so if they were doing back in 70s not sure why our 90s c14 is missing them. I also asked on CN and a chap who recently got a bargain c14 black fork mounted shared a photo and looks like yours , his has the counter weight bars mounted to that plate. Strange ours is missing it, and corrector did not look like it had been taken out before. also the holes are sealed with plastic caps that look factory installed. We also think these caps are not airtight and might be part of the cause for mildew inside.
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