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Naked-Eye Observing - The Moon

It is no surprise that the Moon is on the list for naked eye observing. It is the only celestial object (except our Sun) that can be seen in the daylight (however there have been comets in the past that were bright and large enough to also be seen in the daylight - and Venus can also be visible if you know exactly where to look).

The Moon and its prominent features are easily viewable with the eye. The full Moon does look very large, but you will find that the Moon will be covered by your finger. Your finger will measure about 1 degree while the full Moon is only 1/2º. Click on the image to see a larger, rollover image with labels of the prominent features.

In addition to observing the features of the Moon, the phases of the Moon can also be observed. See the section on the Moon for more details.

Try this neat trick: a full moon near the horizon appears much larger than when the full moon is high in the sky. Is the disk of the moon larger at the horizon? The answer will surprise you - the moon's apparent diameter is ALWAYS 1/2º, both at the horizon and at zenith. This website expands on this illusion.

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