17 December 2007

If wolly fleeces spread the heavenly way, Be sure no rain disturbs the day.

Observing Location	Dennis L Devlin Park, Bronx, NY
Observational Period	1245-1300 EST
Atmospheric Conditions	Cloud Cover Scattered Clouds Temperature 31°F Wind Gentle Breeze gusting to Moderate Breeze Humidity Low Feels Like Cold Wind Chill 23°F It doesn’t feel that bad until the wind picks up. Fortunately it is on the decrease after a can-and-dog storm. Transparency Good Seeing II
Instruments	25x30 spyglass telescope w/Welco gold shade 14 welder's filter - Charlie This was more of an experiment to see if I could observe with this optic than a real observing session since I didn’t anticipate there being any spots left to observe. There is a lot of dirt in the optics so it will be hard to tell the spots from the dust except that the dust will move when I move the scope. It was a little difficult finding the sun but not as difficult holding it in the FoV as I had expected that it would be.
Observing Party	Charlie Ridgway

Target Sunspots Constellation Oph Category Solar Time yyyymmdd.hhmm 20071217.1245 EST Comments Distance Light Time 0.984 AU 8ms Angular Size 32' 33.5" Altitude 25.4° Heliographic Latitude (B0) -1.20° Heliographic Longitude (L0) 148.99° Position Angle (P) 9.14° Carrington rotation number (CR) 2064 Space Weather says that Group 978 is still visible hard on the western limb but I did not see it.   Groups Spots R North 0 0 0 South 0 0 0 Total 0 0 0 R = (Groups * 10) + Spots)

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I was doing some research into precipitation in Exploring the Sky by Day by Terence Dickinson and found a place where he says that it is less than two minutes from the time the sin first touches the horizon until it is completely gone. I did the math and it looks to me like it is a little more than two minutes. The sun is 32.15’ in diameter on average. It travels at 0.25°/min. So I calculate that it should take 2.16 minutes or 2 m 9.6s for it to set.

Time = Distance / Speed

Time = (32.15 / 60) / (360 / (24 * 60)) = 2.16 minutes

Diameter	Time	Comment
31.6’ 0.53°	2.11 min	perihelion
32.15’ 0.54°	2.16 min	average distance
32.7’ 0.55°	2.18 min	aphelion

This is something to try to time if Team TotL ever gets out to Orient Point again to observe the green flash. It would be easier to do it on a sunset when you can see the sun approaching the horizon and know when and where it will touch, but I don't forsee Team TotL making a trip to Florida or out to the left coast to get an unobstructed western horizon.

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Winter Solstice, when the sun will align with one of the sides of the McGraw-Hill Sun Trianggle, is on Saturday, 22Dec07, when the McGraw-Hill plaza will be closed. But it occurs at 0108 EDT which is close to midnight on Friday so I am considering going down to see what happens at noon on Friday. They are saying it will be partly cloudy with clouds increasing through the day and the possibility of more rain on snow.