What an interesting thread.
Got to agree with Peter on this one.
1)_ Recently attented an astro-photo meeting at the ASNSW and Mike BJ did a talk that reflects exactly what Stan Moore is talking about.
2)_ Don't know much about RCs, I trust Peter had enough in his hands to play with and knows what he's talking about. but I know my 5" f/5 newt is very fiddly to collimate from scratch.
3)_ Longer FL harder tracking. Longer tubes catch the breeze. That's a given
Quote:
Originally Posted by Peter Ward
Mark,
1) I was incorrect in quoting Russ as the author of the F-ratio myth...it was in fact Stan Moore. Interested punters can read about it here:
http://www.stanmooreastro.com/f_ratio_myth.htm
Do you disagree with Stan's analysis?
2) You are assuming the primary is decentered by the factory. I've tested close to a dozen of these scopes are not one had a problem. Also last time I checked an F5 of anything was far more of a bugger to collimate than a F8
3) The point Greg made was the *tube was longer*.
It is patently not,
and will suffer less from wind loading as a result....though I do take the point the longer focal length could be more sensitive to seeing and tracking errors. |