Largest Moon of 2009 over the alps (2009 Jan 13)

[Donald Pelletier]

One of my student tell me that the phrase "about 30 percent larger in area" is incorrect. It's not. He forget to read AREA!

At perigee, the distance between the moon and the earth is 363 300 km, for an angle of 0,55°. At apogee, the distance is 405 500 km, for an angle of 0,49°. The variation is equal to 0,06°, about 12% for the diameter. The area of the moon is than (1,12) x (1,12) = 1,25 greater at perigee. So,the variation is about 25%.

[orin stepanek]

http://apod.nasa.gov/apod/ap090113.html
Never the less; it's a beautiful photo! 8) Most full moon photos are though.

Orin

[neufer]

One of my student tell me that the phrase "about 30 percent larger in area" is incorrect. It's not. He forget to read AREA!

At perigee, the distance between the moon and the earth is 363 300 km, for an angle of 0,55°. At apogee, the distance is 405 500 km, for an angle of 0,49°. The variation is equal to 0,06°, about 12% for the diameter. The area of the moon is than (1,12) x (1,12) = 1,25 greater at perigee. So,the variation is about 25%.

So the student was right about the phrase "about 30 percent larger in area"
(assuming that that was the original terminology).

The current terminology:
"about 15 percent larger in area and brightness than a more typical full Moon"
is certainly true for a moon that spends a shorter time at perigee than apogee
and an earth that spends a shorter time at perihelion than aphelion.

[Donald Pelletier]

He show me his calcul base on angle, 12%.
If you take the variation between a typical full moon and the extremes, the result is 12,5%, than writing about 15% is ok.