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Subject: Daytime Viewing
From: Robert Preston
Reply To: mapug@shore.net
Date: Thu Nov 17 08:09:55 1994

Venus knocks the eyes out these days, in the morning sky; gorgeous crescent in a telescope (or even 7x binoculars).

But mainly, I reached a new (for me) magnitude limit for visibility during the daytime: With the sun 14 deg above the horizon, I could see the mag. 5.6 companion in Cor Caroli, which was near the zenith in a not-deep blue sky. Then, while futzing with the planetarium program and sci.astro.amateur for a half hour or so, the rising sun slipped around the umbrella-C-clamped-to- a-stepladder sun shield for the 8" f10 SCT, and in no time the OTA was warm to the touch and even the mag 2.9 in Cor Caroli could hardly be seen due to thermal crap in the tube. Even a half-hour back in the shade hasn't brought back the mag. 5.6 companion 19 arcsec away. I assume it's still thermal distortion-related, although the mag. 2.9 Cor Caroli is pretty crisp.

Mars is real nice, esp with an 82A red filter that raises the contrast a bit by darkening the sky. I don't have a polarizer to try. Easily visible dark markings and bright polar cap.

Mercury is "too close to sun" according to the LX200 ver. 3.20L control pad display, for safe viewing. The planetarium program puts it about 15 deg from the sun: I guess I really don't want to melt my telescope off-axis parts by going manual for a look.

....later: nope, it's not OTA heating that's trashing resolution/contrast, it's just the sun is high enough now, at 10 AM, to heat the nearby roof-tops and so forth. Seeing is definitely getting crappy. Time to pack it up at this site/session. Clouds predicted for the night. Oh, well, I got my astro fix for the day already.