23 March 2006

There is a notice on SpaceWeather.com today about a hoax picture circulating on the internet that is supposed to show a huge Moon hanging over the tiny Sun as seen from the South Pole. It is a nice picture but the explanation goes on to say that it just can't happen that way. That got me to thinking about the relative size of the planets at aphelion/perihelion and apogee/perigee. And that got me thinking about a day when I was out at the park along and someone asked the distance to Mars and I could look it up in planetarium which gave it in AU, but I couldn't put that into miles which is what the questioner wanted. So I decided to create a spreadsheet to do the conversions in my Palm (that will get lost the next time I have to reset but may come in handy sometime before then). That got me searching the Web and got me a reference to a site called Solar System Live (which I notice is at Forumilab which is one of the sites I am seeing a lot recently). It will show you where all the planets are in their orbits on any data and at any time. You can even plug in the orbital elements of your favorite comet and see where it is.

I wasn't able to find anywhere on the Net where anyone has listed the date of closest perihelion and farthest aphelion. I did find that information for apogee and perigee within a 100 year window ending at 2015. So I have had to use this year's sun information with the historical moon data in the following chart.

	Aphelion (typical) Apogee (mazimum)		Perihelion (typical) Perigee (minimum)
	Distance	Subtends	Distance	Subtends
Sun	152,000,000 km 94,500,000 miles	31.47'	146,000,000 km 91,000,000 miles	32.53'
Moon	406,720 km 252,724 miles	29.78'	356,375 km 221,441 miles	33.83

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Observing Location	TotL
Observational Period	2015-2200 EST
Atmospheric Conditions	At noon it is mostly clear with a few passing fair weather cumulus clouds. The NOAA satellite imagery shows a hole in the clouds ovre the NYC metro area. NOAA graphic CSC says it will be clear through 2000 EST then cloud up a little to 10% cover through 0100 EST. Clear Sky Clock graphic But NOAA is saying that clouds will already be at 21% by 1900 EST and will build from there. NOAA graphic AccuWeather is forecasting thickening clouds for the overnight period with the temperature only dropping to 38°F and the winds around 5mph. They are predicting a RealFeel temperature of 36°F. When I went out to dinner it was cloudy but when I returned a half hour later it was clear. I got my gear together and headed out and by the time I got back downstairs it was mostly cloudy but I kept going. When I got into the park it was mostly cloudy but there were some holes, or at least thinner spots, in the clouds. Sometimes you could see a star and sometimes it would be gone. It was a little nippy but there was no wind. I think conditions were worse tonight than what CSC was (and still is) predicting and more in line with the NOAA prediction.
Instruments	SAR: Coulter CT-100 - Charlie I had the scope with me so set it up but didn't use it much.
Observing Party	Charlie Ridgway Kin Lee

Naked-eye Limiting Magnitude Observations	I wanted to do a limiting magnitude assessment for GLOBE at Night but the sky wouldn't cooperate again tonight. I did eventaully see stars down in the Mag 3.5-4 range, but not early enough to count them toward a GLOBE observation.

Target	Saturn
Constellation	Cnc
Category	Planet
Time	20060323.2045 EST
Comments	I could tell that Saturn wasn't round and when it was off to the left side of the field of view I thought I detected space between the rings and the planet on the sides. Saturn does not look as cigar shaped as it used to. This is due to the rings being near their maximum inclination (through 15May06) which makes the view more face on rather than edge on. After seeing the location of the moons in Kin's Tablet PC planetarium program it was fairly easy to pick out Titan off to the west of the planet.

Target	M45, The Beehive Cluster
Constellation	Cnc
Category	Deep Sky Object
Time	20060323.2130 EST
Comments	I looked at M45 early on and all I could see were the bright stars. Later, when it had moved further west, I could see the dusting of faint stars between the gright ones.