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Originally Posted by ramsquire
Earlier this morning in South California, where I am, the moon and Sun were in the exact same portion of the sky. In fact the sun was "above" the moon forming a sort of figure 8.
I'm a beginner stargazer and wondered how frequent does this occur, and what is it called when it happens?
Also, without using a sun filter, can I view the moon when this occurs? both objects were very bright, but considering the moon is just reflecting the light is it okay to not use a filter?
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Welcome to the BABB!
What you're seeing is a result of the Moon's orbit around the Earth. It's what you'll often see referred to as the "phases of the Moon". If we start with a New Moon, we have the Moon directly between the Sun and the Earth and we don't see any of the Moon. As the Moon progresses in its orbit you'll begin to see a "waxing crescent" Moon and you'll notice that it gets higher and higher from the western horizon.
After about 1 week you'll notice that the Moon is half illuminated and is about 90 degrees from either horizon when the Sun sets. This is called a "first quarter" since the Moon has completed 1/4 of its orbit around the Earth. From first quarter onward you will notice more than half of the Moon is illuminated. This is called a "waxing gibbous" Moon. Gibbous is derived from the Latin word which means "hump" or "humpbacked".
After about another week the Moon is "full" and rises on the eastern horizon about the same time the Sun sets in the west. From Full Moon onward the phases repeat themselves in the reverse order. For the next week you will see a "waning gibbous" phase, but this time the "hump" will be on the opposite side from the "waxing gibbous" phase.
The Moon then enters the "last quarter" phase where the Moon is again half illuminated and again is on the opposite side from first quarter. From last quarter the Moon preceeds to a "waning crescent" phase back to a New Moon.
The view you described was during the Moon's last quarter when the Moon rises before the Sun and it appears as if the Sun is chasing the Moon toward the western horizon. Every month, during last quarter phase, you can see this occur.
It's safe to look at the Moon without a filter. However, a really bright Moon can be uncomfortable for some people. Just remember to exercise extra caution if you try to look at the Moon when the Sun is close to it in the sky. Accidently bumping or moving the scope could have some bad results.