Hello, and thank you for the comments.

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I'm curious tho- if a person were willing to create a second (*slightly* shorter) set of truss-poles for BVer mode that would accomodate focus using the OTHER glasspath correctors, the first few you mentioned- would there be an optical benefit in doing so?

I know, it'd make the Dob pretty much a "dedicated" BVer scope for that session, perhaps accompanied by a mono-scope set up adjacent? But if it would alleviate the need for the "fix" you've described, would the image quality deriving therefrom be an attractive option?

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Also, at what F# would you estimate that the abberations you've described would be lessened to such a degree that *you* would consider them negligent. I know, each observer might call that at different points- yet for continuity of thot, i'm curious where *you* would mark it.

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I've already asked myself this question. As a planet and lunar enthusiast, I am actually thinking about a 12" f/5 telescope. It would be less sensitive to atmospheric turbulence, it would reach thermal balance more quickly, coma would be reduced or easier to cancel, and it would nicely accept any optical accessory. For larger Dobs, which are generally limited by turbulence, I would choose f/4.5. Interestingly, I have searched some information about aberrations with fast scopes, and I have learned that SA of accessories (some eyepieces, Barlow lenses, OCS…) increases as the fourth power of 1/f# ! So an accessory can be perfect at f/5, acceptable at f/4.5, and faulty at f/4.

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