USA: Seen: ICOP member Mr. Jim Stamm said:
"I hadn't planned to observe this event, considering it to be trivial. Then Roger Sinnott published a piece about the time interval between opposing Moons. I thought that maybe I could follow the old crescent several hours into the day and then by observing Monday's new Moon crescent, break my old record of 33 hours 9 minutes, obtained 21 January 1996.
This observation was anything but trivial. I wanted to use my technique for pinpointing the location of the crescent despite the prediction of a naked eye crescent - for practice, and to look for ways of improving the technique. It turns out that I needed the technique.
There were intermittent clouds all along the eastern horizon, well up into the sky. However, my plans worked well (except for not getting a limiting magnitude), and I was pointed at the correct location an hour before the Moon would rise above Pusch Ridge.
When the time came, I was on a cloud, but engaging the clock drive, and following the invisible Moon for ten minutes brought it to a break, and the crescent was visible. However, it was too tenuous to be seen in the finder scope, let alone with the naked eye. I followed it for 41 minutes, and the image became less and less distinct. I wasn't able to measure the extent of the crescent with any precision. This was through several deep blue breaks in the clouds. At 06:13 a.m. (local) the crescent faded from view in a clear part of the sky - before the sun rose over Pusch Ridge.
The significance of all of this? Ever since failing to see crescents which were 20-some hours from new, while easily observing them about 17 hours from new, when other conditions like altitude, atmosphere, and elongation were similar, I have considered it a mystery. I usually attributed that mystery to looking in the wrong place, being out of focus, or observing through inconspicuous weather problems. However, I was never fully satisfied with any of those explanations. Yesterday's observation has given me a hypothesis that I have long been considering.
I believe that the reflectance for the edge of the Moon that we are seeking when observing the crescent varies considerably, and this reflectance is more determinant with respect to visibility than the calculated width of the crescent or the calculated percent illuminated. Furthermore, I suspect that the range in this effect is significant enough to become a greater factor in observability than clear sky atmospherics. Finally, I believe that we have a good enough understanding of the Moon's topography, geology, and libration to be able to predict the reflectance.
Old Moon Crescent Observation Report
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Observed: 2008 May 04
Location = Tucson, Arizona (USA)
Longitude = 110.9645 W
Latitude = 32.4204 N
Elevation = 842 meters
Time Zone = -7.0 hours
Surface conditions at time of sighting at
Tucson International Airport (805 m):
Temperature = 14 degrees Celsius
Relative Humidity = 16 percent
Sea Level Pressure = 1008 mb
Significant thin cloud cover in eastern sky, with breaks
Topocentric and local time values from “Accurate Times”:
Moonrise (at sea level) = 04:32
Sunrise (at sea level) = 05:29
Time from new moon at 06:13 = 22 hr. 11 min.
Moon lag time = 57 min.
Relative Altitude = 11.3 degrees
Elongation from sun = 14 degrees
Crescent width = 30 arc seconds
Illumination = 1.5 percent
Crescent first observed through 8” SC telescope:
Time = 05:32
Altitude = 10.1 degrees
Final observation with telescope:
Time = 06:13
Altitude = 18.4 degrees
Observer(s): Jim Stamm
E-mail Address: StammJim@gmail.com"