Piggy backing on C14

[Dawson]

I’d posted this on SGL but want some more feedback than I got there.

Currently, we have a C14 sitting directly to the saddle of the EQ8 via a Celestron 24″ long orange dovetail, and a second 24″ dovetail opposite this one is on the top of the C14 and it has rings with adjustable bolts to align an 80mm refractor to the C14.

I’m not too worried about flexure as we are not doing long exposure astrophotography, I just would like a second refractor on the setup so one can be left with a camera attached for video astronomy and the other with an eyepiece.

Aside weight, and balance, are there any obvious issues with moving the top dovetail and having three dovetails evenly spaced around the C14 like in the second image below? The first image is the current set up. Someone on SGL suggested side by side but for some reason I just don’t like the idea of that.

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[Richard Sargent]

Hi James,
I’ve just looked at my C14 OTA (which also has the two dovetails arrangement you described on yours) and although there are pairs of drilled holes with screws in at the locations you show in the second image they are only at the rear of the OTA and look to be for the finder. The distance between the holes is roughly a centimetre shorter than the distance between the mounting holes in the dovetail. I haven’t checked if the screws are the same size as those used with the dovetail, they might be smaller. So you would have to consider drilling and tapping holes in your C14 at front and rear of the OTA which would be way too scary a job for me!
Good luck, Richard

[Dawson]

Thank you Richard. I should have said that; yes I’d need to drill holes in the front and rear collars of the C14, which isn’t difficult to do once the corrector plate and primary mirror cell are removed. I was potentially going to use the opportunity to install a fan or vent at the back at the same time to help with cool down.

[Grant Privett]

Could you supply a link to the SGL discussion?

Also, why not use an OAG and the existing top rail for the refractor?

[Dawson]

Grant,

Here is the link to SGL: https://stargazerslounge.com/topic/424477-maximum-payload-eq8/

I am not seeking to guide, I am seeking a second refractor to [semi-]permanently fit with a camera to project an image on a TV, leaving another refractor with an eyepiece and the C14 with an eyepiece.

Thank you.

[Michael O’Connell]

I’m not a fan of side by side for balance reasons.
I also don’t like placing a heavy scope on top of a SCT.
The torsion of a heavy scope at top of the SCT combined with the torsion of the SCT on to the mount may be applying quite a strain on the OTA strucure that I wonder does it place pressure on the corrector glass?
I would suggest Parallax rings.
Michael.

[Dawson]

Michael, thank you.

Valid point. I suspect most of the additional weight will be on the rear cell of the C14 which is pretty thick and very rigid. I don’t think as much weight and potential distortion on the front cell. I am off to the International Astronomy Show in a few weeks so I’ll speak to people there. The only rings I’ve seen for the C14 are over £1000 which seems crazy, and I do wonder if the thin skin of the scope is better or worse in terms of stability and applying forces through/over the C14.

James

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