Friday, September 11, 2009

Seeing the Moon in Daylight.

The Moon in daylight. Left image, standard photo, right image, photo through polaroid glasses.

As long time readers of this blog know, I'm very enthusiastic about getting people to see Venus and Jupiter in the daylight. But did you know you can see the Moon in the daylight?

Now the dedicated astronomer types here will be going "What do you mean? Of course you you can see the Moon in daylight". Some others of you will remember a nearly full Moon rising just before sunset.

But many people have never noticed the Moon in the daytime sky. The Moon is a lot paler in the daytime sky, and can often be easily missed or or its pale aspect mistaken for a cloud. Also, for most of us living in suburban and urban settings , the sky is often a narrow band broken up by buildings or other obstructions, so seeing anything in the sky is a bit haphazard if you don't know where to look.

And of course there is clouds, we won't talk about clouds.

As well, when the Moon is at is largest, near full, it is only in the daytime sky for a short time, low to the horizon. Even today, as I write, the nearly last quarter Moon is low in the daytime sky, two hours after sunrise. Still, overall the Moon is visible in the daytime sky for a fair amount of time between full and three days before new Moon. You can actually see the crescent Moon two days before new, but it is very close to the Sun, and much care is needed (and often binoculars). In the past, I've had to use daylight Venus to help me find the thin crescent!

To find the Moon in the daylight it helps to have a good idea of where it is at night. After full it is relatively easy, you can see where the Moon is just before Sunrise, and can keep an eye on it after Sunrise. In the daylight, a lot of the moons features are easier to see with the unaided eye, as they are not lost in the glare of the Moons brightness. You can use polaroid glasses or filters to help see the Moon. Unlike Venus, whose light is strongly polarised, using polaroid filters cam increase the contrast between the Moon and the sky quite significantly (the images above don't do the actual increase justice).

Before full, you can use a newspapers Moon rise and set times (often up the back) or set of astronomical tables (or tide time tables) to find when the Moon rises, and scan the sky (wearing polaroid glasses if you like) for the Moon. Or you could see where the Moon is the previous night just after sunset, then, remembering that the Moon is around two hand spans further on each night, look in the approximate position the Moon was the next day (but two hand spans over).

We often think that astronomical activities cease when the Sun rises, but for the Moon and bright planets, it's not really over. Happy Moon hunting!

This is the fifth of a planned series of posts on looking at the sky and how to find your way around it as a beginner.

First post: The Dark Adapted Eye.
Second post: Let the Moon be Your Guide
Third Post: Seeing the Emu.
Fourth Post: Cloudy, Cloudy Sky


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