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Introduction
Introduction
This project will consist of a 22" f/2.8 meniscus mirror made out of BVC, and a telescope based around it. The 22" is to replace my 24" scope, which is currently pending sale. The blank weighs only 38 pounds, which is not the lightest but it's better than the 60 pounds of the 24". It's 1" thick with a 0.5" deep curve (sagitta) so it acts about as stiff as a 1.5" thick typical blank, which most people would consider fairly reasonable. I could've gone thinner but wanted to alleviate the risk seeing as it's already going to be the largest and most difficult mirror I've ever done.
The finished scope will be 5 feet tall, less than 70 pounds, and fit in a Prius if need be. The idea is to have a fairly convenient instrument that acts more like a scaled-up version of my 14.7" scope and less like a dinosaur Obsession clone. Using composite construction, etc. this is feasible.
Update 1- 3/5/22
Update 1- 3/5/22
Bit of an update: Blank #2 (B) is here. It's 1/4" smaller, slump is a bit better, weight difference is about 1 pound. The diameter and mass difference may pose a challenge in any attempt to swap the mirrors out of a single structure, so I surveyed my options.
1. Binoscope
This has been a thought from the beginning, but I've basically axed it at this point.
Pros: It's a binoscope, more light gathering ability
Cons: Bulky, heavy, collimation hell, large secondary mirrors needed which balloons budget, pairs of eyepieces and coma correctors make it essentially non-viable price wise
2. Make the second scope into an astrophotography-oriented instrument
Pros: Unique purpose for both scope
Cons: Cost, complexity in adding guidable EQ platform or driven mount, I don't really do astrophotography
3. Just find someone else to grind the second blank
Pros: I get a bit of money back, don't have to worry about dealing with 2 mirrors
Cons: I only get to keep 1 mirror
I ultimately went with #3. I have a friend in California who wants to turn the second blank into a mirror, so after both blanks are smoothed out front and back to #220 I'll be sending one his way.
Additionally, the grits are on order, I seem to have found a grinding machine that may help some of the process, and the 24" is on its way out.
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