Gosh Tel....

Just wondering if you ran the batteries in you calculator down doing all that math.... LOL

Even if you did the above is another GREAT post from you....

However I not really that sure at what point a Focal reducer fails to be effective (or offers anything worth the effort) ...I seem to remember reading that one gains nothing if you use one with any possle eyepiece less then 12 mm.

I just do not know...

Bob G.