Obs Notes: Venus and Mercury at sunset 8-17 to 8-23
On 8/17 through 8/23 at sunset, Venus (-3.9) and Mercury (-1.1) will be visible within a 1.2 deg eyepiece view. Venus and Mercury will be at approx. 275 az alt 8 at 8:20pm MDT each night. Venus becomes naked eye visible at around 8:35pm, allowing for easy target acquistion. On 8/16/2008 2:20UT (8:20 MDT), I watched Venus and Mercury (Saturn was not visible) with 10x50 binos and a smaller 70mm refractor for the purpose of getting a feel for the visibility of this wide conjunction. The following are my notes on visibility as Venus set between 8:20pm MDT and 9:00pm MDT: 8:20 MDT - Venus visible telescopically at approx. 7 degs alt; 275 az. Venus phase easily seen in refractor at low power. Sky Quality Meter ZLM 8.7 MPSAS (-5.5 mags). (The sky was much brighter near the horizon.) Unable to detect Saturn or Mercury. 8:35 MDT - Venus visible the naked eye. Sky Quality Meter ZLM 9.5 MPSAS (-4.2 mags). Mercury not detectable visually or telescopically. 8:56 MDT - Mercury first detected telescopically about 1.5 degs from Venus - but only 2 degs above the horizon. Mercury was only visible for a couple a minutes before being obstructed by a horizon object. Sky Quality Meter ZLM 13.1 MPSAS (-0.6 mags). Zero magnitude stars just coming out within 25 degs zenithal distance. ~9:05 MDT - Venus sets. Saturn (1.1) was not detectable at any time. For this evening (8/17 to 8-23), Mercury should be much easier to detect telescopically in the same AFOV as Venus, earlier in twilight and at a higher initial altitude. - Kurt
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Canopus56