Adding another scope on top of one insitu

[stephen2615]

Greetings,

I have a Celestron EdgeHD 9.25 and a 115 mm refractor (and a WO Z61). I have a dome on the way and I was told that the NexDome 2.2 has an aperture of 61 cm and it probably would not cope with a side by side solution for the two scopes given the diameter of the EdgeHD.

So the suggested solution is to put the refractor on top of the reflector. I have a Losmandy plate designed for the EdgeHD on top of the scope. It is held there with three small screws that screw into the EdgeHD. I am concerned that those three little screws and whatever is inside the EdgeHD that the screws screw into can cope with about 12 kg (minimum) of the refractor sitting on top of it.

I have an EQ8-R so payload capacity is not an issue. Has anyone tried doing that with a reasonably heavy refractor on top of the reflector. If I get carried away, I am considering putting the WO Z61 on top of the refractor. The pics I have seen have small refractors sitting on top but their weight wouldn't be anywhere near a min of 12 kg. TIA..

I know you can get bespoke parallax rings for the EdgeHD for a considerable cost that are made overseas.

Stephen

[Peter Ward]

Use a Losmandy DVSBS.....it will allow easy addition/removal of various OTA's, be more rigid and have a lower moment of inertia than any piggy-back configuration.

[Startrek]

I currently use an 8” f5 newt ( tube diameter 240mm) with an Orion 60mm guide scope piggy backed on central axis in my NexDome and works great with plenty of clearance
In July I’m upgrading to a 10” f5 carbon fibre newt ( tube diameter 305mm ) with an Orion 60mm guide scope.
I use my own custom made Dome rotation control for Azimuthal movement which works well up to 70 degrees in Alt ( beyond that altitude I revert back to periodic manual tweaks of the Dome rotation )
The 610mm slot in the Dome will be fine for a tube diameter of 300mm and say small refractor piggy backed provide you have the Dome rotation automated with Voyager or some other software system
I think the NexDome is designed to handle up to a 14” SCT
To make the Dome slot wider would inhibit the benefits of using a Dome Obs ( stray light , wind and dew etc... )
Hope the above helps

[stephen2615]

As I mentioned in my original post, the 61 cm aperture probably isn't wide enough for a side by side setup. The information provided by the vendor and the manufacturer said it can cope with a C14.

The two scopes side by side on a table account for about 50 cm so using the DVSBS, I will be pushing the limits to see out of the aperture at various angles.

[stephen2615]

The small guide scope is a lot less weight than the refractor I have. I don't know how sturdy the tube you have is but if you could see the little screws on the EdgeHD, I am sure you would be holding your breath if you put a 12kg scope on top.

Considering that the screws are designed to put gear on top, it would be great if Celestron and other manufactures could provide a load rating of those screws.

I have tried searching for say m 3 load rating but most sites stop about m 5 sized threads. The available numbers don't give me much hope.

The C 14 is about 30 mm wide, my two scopes sitting side by side with some clearance is about 50 mm wide.

[Dave882]

I’ve had an ed80 and basic imaging gear piggybacked on my c8 edge using the top orange celestron d-type rail and vixen adaptor clamps. That’s probably not quite 12kg but at no stage did I feel it was unstable and would have been comfortable with a bit more weight.

Edit: Actually just realised I had a photo of the setup minus imaging gear…

[stephen2615]

That's good to know. Thanks. I will have a try attaching the refractor and see how it feels. That rail of yours would be using the three small screws that the SCT has?

[Dave882]

Yep -2 at the back and one at the front. Pretty solid on mine.
The orange celestron tail is figured to the curve of the ota and I’m sure that helps with the solid fit.