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Old Moon 20 hours from New (aka Old Moon Spotting)

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#1 Dave Chapman

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Posted 09 February 2013 - 01:23 PM

Here at the Winter Star Party, we rose at 5:30 EST to prepare for moonrise at 6:14. There were few clouds, but the haze was thick for a couple of degrees at the horizon. Before dawn's light, I measured an SQM of 21.5 away from obvious sky glow. Greg Palman slewed his Go To 6" refractor to the Moon shortly after moonrise and was the first to see it with optical aid. Quinn Smith found it in his ED80, and used the red dot finder to locate the point in the sky to look with the unaided eye. I found it in  binoculars but could not see it unaided, until I used Quinn's method. The time was 6:26 EST, 12 minutes after moonrise, 36 minutes before sunrise, at an altitude of just under 3 degrees. After this,we could not maintain unaided eye contact, as the sky was brightening. While searching for the Moon, I snapped several exposures with a Canon SXi and 300 mm lens to set the background brightness, and I later discovered that I had captured it on several frames around 6:19. Here is one of them, cropped but otherwise unprocessed: http://flic.kr/p/dTpL7F

Venus rose after the Moon. For a short time I saw both the Moon and Venus in binos, and then Venus unaided, but never the two together, unaided.

This observation was aided by several factors: an ocean horizon, clear (although hazy) skies, a moderately steep ecliptic angle at the sunrise azimuth, the Moon being north of the ecliptic, and 12 degree elongation from the Sun (perigee was Thursday), not to mention alert, prepared, and experienced observers! Quinn and I had made a dry run the previous day, and we were talking about it at night, so a small group joined us to look, while everyone else was in bed or actually packing to leave.

Dave Chapman

#2 Centaur

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Posted 11 February 2013 - 12:21 AM

Thanks for your fine report and photo of the Old Moon, Dave. It's been hard for me to get folks involved in an Old Moon spotting challenge, due to early morning requirement.

Glad you were able to take a stroll along the coast to visit the Keys. We're just waiting out a relatively mild winter here in Chicagoland, but nevertheless winter.

#3 rookie

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Posted 11 February 2013 - 09:36 PM

That's a beautiful picture Dave! Great catch. The preparation and readiness was worth it. :bow:






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