I'll have to admit that I don't have real life experience supporting 4" refractors - although I'm planing to gain some soon.
My weight calculations come from 4" f/7 scope like the AT102mm ED (9 lbs), alt-az mount like the Stellarvue M002 w/ column (6.5 lbs), and carbon fiber photo tripod like the Robus RC-5558 (5.5 lbs). This leave around ~ 5 lbs for visual accessory’s. Simple red dot finder and 1.25" diagonal and eyepieces should theoretically squeak the whole shebang in around 25 lbs - in theory
In reality 35 lbs would still be fine by me. In the end I find the shape and placement of the weight while moving more important the final weight.
I'm always willing to learn more, please share the set up that you find adequate support for a 4" scope. I think this would be useful knowledge for me and the OP. If they're seriously considering a 4" they may need to flex their max weight requirement.
I had my TV NP101 on a DiscMounts DM6 and DiscMounts wooden tripod for a few years. It’s more mount than necessary for a 4” scope, but I also used it with Tak Mewlon 210 (8”).
My current 4-inch class mount is a DiscMounts DM4. DiscMounts recommends a Berlebach UNI-18 wooden surveyor tripod for this mount. Tom Peters designed the DM4 for a 4-inch refractor.
I found it pays to be very skeptical of published weights because they are often more aspirational than actual.
To me, the potential for a wide field of view one of the most attractive features of a small refractor, so I use heavier 2-inch accessories with mine.
A 4” refractor often needs an extension column between the mount and the tripod to allow scope to point at the zenith before it hits the tripod, which adds about 3#.
I would be wary of using a photo tripod under a 4” refractor unless I had prior personal experience with it and knew it was capable of solidly supporting a scope of similar weigh AND length.
Unquestionably you can assemble a 4” refractor, mount, and tripod that weighs 25#. The question is whether the scope will work well enough to satisfy you. When I slew my scope to a target and remove my hand, I want the scope to stop instantly without moving or shaking, and the image shouldn’t jiggle while I am focusing. For this kind of performance, I think 35# is a more realistic minimum weight budget, but I think it might be possible to take a few pounds off with a high-end carbon fiber tripod like a Gitzo Series 5, but I haven’t tried it yet.
Edited by gwlee, 26 November 2020 - 07:39 PM.