birding with big cat scopes

I have a c5 spotter, does anyone use any bigger ones, and
is there any benefit to using a bigger one for terrestial
viewing, I read an article that said nothing compares to
the view from a mirror rather than a prism. thanks in
advance for any thoughts.

I have used a 20-60X 60mm Celestron spotting scope, 80mmF5 short tube refractor and a Meade 4" SCT for terrestrial viewing. Have not tried anything bigger. None of the above socpes offer outstanding optics. The Meade SCT is OK with the supplied 25 mm MA eyepiece(40X) but dim with the 9mm(111X). My 80mm F5 gives sharp view of the planets at 88X(with 2X barlow). However, both scopes are awkard in daytime use with the 90 deg diagnol, reverse image and narrow FOV. IMO there is nothing much to be gained by going to a bigger scope in terrestrial viewing. The atomsphere rarely premits much more than 80X and you don't need larger objective to collect more light.

I am quite interested in the 100mm Pentax ED though. It's little brother, the 80mm ED, has received rave reviews here and elsewere. Since over 50% of my scope use is for astronomy from my backyard the 100m Pentax appears to be a great dual-use scope. It's also about 1/2 the price of a TV-101/102. I wonder how it would perform with a premium TV eyepiece at 100-120X compared to a Tele Vue APO?

Erik D