Conventional wisdom (CW) in astronomy:
(1) CW: A larger telescope is more affected by bad seeing
Truth: A larger telescope is affected the same by seeing given same magnification, but it may not live up to its higher resolution potential except on good seeing days (or never, if it's a 24"
(2) CW: Quality APO refractors are the best planetary scopes
Truth: Quality APOs do perform as well or better than other telescopes of same aperture and quality. They are also the by far most expensive scopes per inch of aperture/photon collected/arc sec resolution, bar a few handmade and rarely sold other types.
(3) CW: The central obstruction in SCTs (or most other reflectors, for that matter) greatly reduces contrast
Truth: The central obstruction in SCTs slightly reduces contrast. Consider that practically all professional telescopes built in the last 100 years (ground or space-based) have a central obstruction, and if they are Ritchey-Chretiens, which many are, a rather large central obstruction at that!
(4) CW: Binocular viewers are only good for bright objects because of the light loss
Truth: Quality binocular viewers are good for all objects. The brain makes up for (almost all/all) of the light loss so that only on very dim objects at the edge of visibility there may be a difference in what can be seen.
(5) CW: Beginners need to learn star hopping first
Truth: Depends on if you like the journey or the destination! Seriously, not finding objects is the largest reasons for beginners to ditch the hobby. Not having to star hop does not preclude anyone from "learning the sky" if they so desire. And, most beginners observe mostly from their light polluted back yard, and star hopping to objects never seen before using a few dozen visible stars is very challenging event for experienced observers to say the least!
(6) CW: Aperture rules
Truth: Almost true. Aperture rules as long as the scope isn't to large/heavy to be used. Resolution increases linearly with aperture, light gathering with the square of the aperture, and weight almost with the square of aperture. But: Aperture = power, not magnification = power (as anyone who ever owned a 50mm Tasco refractor knows quite well)
Woohoo! Let's get this show on the road.
And - it's OK if someone else but the three APO musketeers (it's all in good fun, right?) posts/flames/(or dare I say) agrees!