Last night headed out with the 76mm Sears 6339a under a reasonable sky (border between bortle 5 & 4). First clear weekend evening for a while! Removed the draw tube and experimented with the number of extension tubes needed for getting 1.25" eyepieces (w/diagonal) to focus. One 2" thread-on and one 2" inserted extension was needed and still had to pull out the extension tube by about 1" to get the eyepieces to focus. The inserted extension has a long barrel so pulling it out a bit wasn't a problem. Used the Interstellarum atlas...Not sure if I'm a fan yet...more used to Uranometria.
From what I remember:
Gamma Andromedae: great colored pair
Gamma Delphini: yellow primary with off-yellow secondary
Gamma Arietis (geez, lots of gamma's tonight): Tight white pair, similar magnitudes
Eta Persei: Nice orange primary with distant and faint secondary
Lambda Orionis: Tight white pair of unequal brightness
M15 (globular): hints of graininess along the edges but no clearly resolved stars at 160X
M37 (open): Super nice! dusting of faint stars, best view with 16mm Konig
M57 (planetary): small but obvious at 50X, dark center at 100X
M77 (galaxy): obvious at 75X, but in within the local light dome. The nearby 10th mag star was visible.
NGC7006 (globular in Delphinus): Faint and small, but clearly visible.
NGC772 (galaxy in Aries): Actually, a no-sighting...some potential hints, but no confirmation
NGC1746 (open in Taurus): large and poorly concentrated center; sorta nice @ 50X, sorta unrecognizable as a cluster @ 100X
The big score: Comet Wirtanen: situated on the border of Eridanus and Cetus. Found in 8" f/6 dob @ 50X. Large and diffuse with brightish center, but overall quite faint - averted vision was needed for it to pop out.