Jim, that sounds like a good point to design around. Long enough F# to avoid most of the off axis aberations, short enough you do not have to climb too high on the ladder. It will still take up a fair amount of room for transportation though. Do you plan on making the mirror yourself, or have Steve build it? John Zeigler -----Original Message----- From: Gibson, Jim [mailto:gibson@dpg.army.mil] Sent: Wednesday, October 01, 2003 2:57 PM To: 'Utah Valley Astronomy Association' Subject: RE: [UVAA] Scope Length John for 110" I could go for a 20" mirror with a f5.5 ratio. That might be the best compromise. Thanks Jim