Formerly I asked somewhere (or someone else did) how come that strange 9 1/4 aperture size.
8 was first, 11 followed then came the 9
First, there's definitively a huge gap between the 8 and the 11. It's still large between the 9 and the 11.
Now both scopes seem to exactly or closely share the focal lengths of their primary mirrors.
So, another scope size using the same mirror curvature, maybe the same mirrors cut down to the new size yould yield some synergetics. This applies to both, primary and sec. mirror. No change of curvatures for a new 9.25" scope
The 9 is a pre edge design. The aim was a significant coma reduction fitting the new scope to ap (APS C size those days was great)
Then this 9.25" inch size was a compromise at: significantly larger than 8 and significantly less coma than 8 by a significantly longer primary mirror.
Strange only that as far as I can tell the 11, too shows significantly less coma than the 8 already.
But the 9 does still better and it fills the size gap, so worth it anyway. Maybe the 11 was half the way to imaging which the 9 was supposed to complete at a more convenient size
Edited by quilty, 19 April 2025 - 06:26 AM.
