Here's an update on the transition of C-11 to C-8. Both optical tube assemblies (OTAs) will remain available for use. Here are the OTAs and mounts that I have available:
Having 4 of the larger OTAs utilizing the Losmandy G-11 mount, shows the wisdom of devoting a considerable fraction of financial resources into a capable mount. So now I'm equipping the Losmandy mount with the C-8 and AT115EDT refractor on top. The C-11 will be in semi-retirement for the time being.
Here's a photo showing that combination.
This photo shows the Dollond spyglass atop the C-8 in test mode.
The above photo shows the orange Celestron D-style dovetail plates, top and bottom.
I have become concerned about the strength of these dovetails in supporting the loads imposed. Each is connected to the Celestron-8's end castings by 3 very small allen-head screws, one on the corrector casting and two on the rear casting. Now these screws have a very high tensile strength, and are not in danger of breaking. But the dovetail plates themselves, along with the threads in the casting holes are sources of concern.
Each dovetail is an aluminum extrusion, that contacts the end castings only at the outer edges. It is not shaped underneath to match the curvature of the optical tube, as shown in the next image.
This shows the 4mm gap below the dovetail on the corrector end. At this location it is held by a single allen-screw in the short slot visible. Now my concern about this attachment is not that it might break - it all seems pretty solid. But one dovetail on top supports in excess of 15 lbs. of refractor, tube rings and dovetail clamps, all on top of the C-8 OTA. But the dovetail directly connected to the mount carries all that weight plus another 15-20 lbs. of C-8 OTA, finder, DewBuster, Dewshield, 2 dovetails .... Well, all this adds up 30-40 lbs. (14-18 kg.) being supported by three small screws, holding an extrusion that is not in good contact with the OTA front/rear castings. This was a concern to me.
So I decided to buy a pair of Parallax C-8 tube rings. Astronomics had one in stock for $220. When I told the telephone sales person of my concerns (I forget his name), he suggested a less expensive alternative - that is two Losmandy C-8 dovetails for $190. This is shown below.
He explained that the two curved dovetail blocks give a much more secure and stable connection than the orange Celestron dovetails. Supplied with the Losmandy product are high quality stainless screws needed to connect to the OTA. Further he said with the parallax tube rings, securing the orange dovetails to the flat boss above and below would not be a very secure or stable connection. He recommended against that in favor for the less expensive Losmandy product. I appreciate the knowledgeable staff at Astronomics.
Now they only had one Losmandy dovetail in stock. But that will replace the lower dovetail carrying the most weight. Later if I decide to replace the upper one, I'm still money ahead over the less suitable Parallax rings solution. So with the dovetail and a lens brush to get over $100, shipping was free. The tracking number shows they send the parts via 2-day FedEX. Kudos to our Cloudy Nights sponsor - Astronomics.
So that's where I'm at with transitioning to my old Celestron-8 on the Losmandy mount. I keep you'll posted.
Edited by Rustler46, 05 January 2021 - 02:41 AM.