Site that will tell me when the moon will show up at a larger size?

[ziggie216]

There were couple of nights during this winter where the moon was showing up ether double or triple of its usual viewable size for probably an hour or so. Any chance there is a website that will tell me the day, time, and location of when this happens?

[Josh_30]

I think that's just an optical illusion, considering that would involve the position of the moon in relation to the earth to shift a great deal in a short period of time. But generally the moon looks larger when its near the horizon vs when its up in the middle of the sky.

There is a difference in distance between the nearest and farthest distances during lunar orbit, but nothing that would contribute to a 2-3x enlargement.

[gjl711]

Then there is photoshop. you can make the moon any size you can dream up. :)

But here is a description of the moon at perigee and apogee:
http://www.fourmilab.ch/earthview/moon_ap_per.html

And buried in that page is the perigee/apogee calculator.
http://www.fourmilab.ch/earthview/pacalc.html

[A.S.I.G.N. Observatory]

The moon only looks bigger when it is near the horizon because you have a known point of reference to compare it to. If you held a disc at arms length that would hide the moon exactly, you will find it will be the same when it is straight up.

The full moon rises once a month and it takes a while to learn it's times of night for rise and set by heart. There are plenty of moon phase calculators online to plan your viewing sessions to catch it at it's fullest just as it cracks over the horizon.

A lot of people say to me, "Wow! did you see the moon the other night? It was HUGE! Was there something special about that? How often does that happen?"

I usually say..."ho hum...yeah, every month dude.....but you are probably never outside looking for it so when you see it by chance it may seem unusual."

[hollis_f]

The best explanation for the moon illusion (where it looks much larger when close to the horizon) is that we don't perceive the heavens as being a perfect hemisphere. The human brain is used to things on the horizon being a long way away, whereas things overhead are normally a lot closer. So the sky is more of a shallow bowl than a hemisphere.

When we see the Moon overhead we see something that's 0.5º wide and fairly close - so the brain tells us it's fairly small. But the same Moon, still 0.5º wide, on the horizon is, according to out brains, a lot further away - so it must be bigger than the overhead Moon.

This sounds more plausible than the 'point of reference' theory; if only because the effect is more pronounced when the lanscape is flat and featureless (desert, sea) which makes the horizon seem even futher away.

[tiger roach]

The moon does get a little larger and smaller since its orbit is elliptical, but not by a lot (nothing like 2-3 times its normal size).

This link explains the phenomenon, and includes a link to a calculator if you want to see when to catch the moon at perigee.

http://www.fourmilab.ch/earthview/moon_ap_per.html

[ziggie216]

Thanks for all the info. When I see the moon "bigger" it's usually in a dark yellow color as well compare to the "normal" size I see from my location which has the gray color.