The geometries for solar and lunar eclipes are:

Solar Eclipses: Occur Only During New Moon

Lunar Eclipses: Occur Only During Full Moon

The complete blocking of the Sun, the dark shadow is the Umbra. The partial blocking of the Sun, the incomplete shadow is the Penumbra. If the distance between the Moon and Earth is too large, the umbral shadow will not reach the Earth and we will have what is called an Annular Eclipse.

In general, far more people have seen total lunar eclipses than total solar eclipses. Why is this true?

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Moon is reddish during total eclipse

Setting Sun is reddish

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We see that solar eclipses may occur when the moon is new and lunar eclipses may occur when the moon is full. Wait a minute. New moon and full moon occur every month but there are eclipse seasons which recur roughly every 6 months (during eclipse seasons).

Why don't we have eclipses every new moon and every full month?

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Upcoming Eclipses

A nice reference: eclipse.gsfc.nasa.gov/eclipse.html

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Eclipses (Transits) in Extra-Solar Planetary Systems

There is nothing unique to the Sun-Earth-moon system that restricts eclipses to only them. We can also get eclipses (known as transits) when the planets Mercury and Venus pass in-between us and the Sun. As a neat use of this idea (phenomenon), one of the most powerful methods currently utilized in searches for planets outside of our Solar System, is to look for transits of extra-Solar planets in front of their own stars (see the Kepler and TESS missions). We will spend much more time on these missions later.

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