first calculation if the primary is an f/3.26, the amp would be 12/3.26 = 3.69x
This was my calculation as well.
In you first part, using a f/3 primary with a separation of the mirrors at 324mm. I come up with a secondary diameter as 44.8mm. You say the diameter is actually 48.5mm, so I don't know what the problem is there.
Well, I do. As I said in this constellation I would have useless CO, the sec is 6 mm too large, or 4 mm in your calculation. But this was the case if the primary mirror was a f/3 which supposition you find everywhere and this is not reality.
Primary f/3.25In this one, the amp is 452/137 = 3.29x, for a system of f/10.75.
Your number do not work, as this is not a f/12.
As I already said, I don't mind if the resulting scope is f/12 or f/11 or f/13 I just want no castrated one. And at f/11 maybe a hyper primary would do better, I don't mind that neither, for I had more aperture and less CO THOUGH f/11 instead of f/12. And this shows why the actual design is not perfect. And why doesn't that make sense?
In this one, p = 136, (460 - 324). p' = 324 + 100, or 424mm. So the amp = p'/p = 424/136 = 3.11x.
But for this example, the secondary needs to be 50.1mm in diameter.
The last two examples are puzzling me. When you calculate f primary times power secondary and f primary is f/2.85 then the secondary power should be more than 4x,shouldn't it? And is logical for curvature must be higher to better collimate the mor inclined light rays from the primary, correct?
But in the last example an f/2.85 primary needs just a 3.11x secondary, that I cannot understand.
Or, this way, 3.11x2.85 would yield an f/8.8 total wouldn't it? Great, faster than the RC while less CO and more aperture!
Again, my secondary inner diameter is 48.5 mm, mirror distance is 324 mm (depending a bit on collimation setting), the primary dia is 150 mm. The true aperture is 138 mm. The rest is calculated using ray set (do you say so, just considering at what distance the circumference light cone reduces to the sec size and to nought at the focal length. And this yields a focal length of 489 mm while direct measurement yields 49 +-1 cm which matches very good.
And again, designing the scope mirrors while mirror distance and scope dimensions is fix given would mean, the resulting f factor may be not at free choice, ok then, I don't care. Better having an f/13 or f/11 6.3 inch scope at 38% CO than an exact f/12 5.4" scope with 44% CO, true?
Better dropping a good friend than skipping a bad joke
Edited by quilty, 26 October 2020 - 12:48 PM.