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"Rank Amateur" wrote in message
link.net...
Last night I attended a star party here in Central Texas. The seeing
was
unusually good for this area, and, among other things, I observed the
Trapezium through three SCT's -- an old orange-tube C8, a brand new
one-arm
C8, and a recent-vintage Meade 10". Through the orange tube, the
Trapezium
stars were beautiful, sharp points and the E and F stars easy to see.
Through the other two scopes, the Trapezium stars appeared a bit "dull"
and
lackluster, and the E and F stars were barely perceptible.

Was the orange tube just an unusually good SCT, or maybe it was just
better
collimated? The eyepieces and diagonals were comparable on the two
C8's,
and the Meade had high-dollar TeleVue eyepieces and diagonal.

I tell you, after observing through the orange tube, I am convinced that
SCT's can give excellent views.

Any of those scopes should have shown the Trapezium with all six stars
crisp and well defined, given the kind of seeing you describe, and the
fact you saw them that way in one of the scopes. The other scopes may not
have been properly collimated, may not have been in thermal equilibrium
with the surrounding air, or both. But they should all have shown all six
stars sharply if one did. And the 10" easiest of all... Could be a bad
scope, but chances are, it was collimation and/or equilibration...