Sunday, February 12, 2012

Moon Perigee

My impressions from the last (2012-05-05) are in the following article

The moon orbit around earth is quite ecliptic and the moon distance can vary a lot within a lunar month. At perigee, which is the nearest point in its orbit to Earth, the distance is about 367,000 Km. The point of greatest distance is called apogee and it was more or less 402,00Km . The perigee and apogee points' distances change each month and the minimal perigee is 356,000 Km while the maximal apogee is 406,000Km. Again, the cause for the distance difference is the moon orbit which is not circle but, like all other orbs, elliptical.
This distance's difference make the moon looks slightly bigger in its perigee. However it is very hard to notice this difference with the naked eye. The perigee and apogee point are in different moon phases, and there is no easy way to compare them, but taking photos and put them side by side. 
Even that is not so simple. The moon is in different phase, and in different angle. The best option is to wait until a full moon apogee and a full moon perigee. Patience is needed but the result will be better as demonstrated by Anthony Ayiomamitis photo  which shows the difference very well.
Here are two photos from February 2012. The moon at perigee (the right photo) and the moon 10 days before it (A little after its apogee). Can you see the difference? Try and calculate it and see what are the results. Take into account the fact that when the moon is low in the skies it is a little further (Add some of the radii of the Earth) to the distance. This difference can be about 1-1.5%
Moon at Perigee and Apogee. try to compare the size
Moon at perigee and apogee. try to compare the size

Also, do not mistake a perigee moon with the large moon illusion or the orange color of  a rising moon which are different (and in my opinion, more interesting)
Orange moon rising. It looks large to the naked eye due to the large moon illusion. It is also a supermoon.

During 2012 the moon will be full at perigee on May 6 2012. The moon will be exactly full on its minimal distance of only 356953 Km and in apogee on 28th of November (406364Km). These dates are the best to take photos and compare the moon size.
Here is the Moon from May 5 2012 - Known as Supermoon of 2012. The comparison photo will wait a few months.
Supermoon May 2012
Supermoon May 2012