[jagswolves]

After the full moon, with the shadow on the upper part of the moon, there is a shadow-like notch separate from the shadow cast by the moon. If the moon was a clock and the hour hand was at midnite, the notch would be at the 12:16 or 12:17 position. I have noticed this more than once in the past months and would like to know what is casting this additional shadow on the moon? Outside of the Earth aren't Venus and Mars the only thing that could be casting as shadow? Or possibly some type of comet? I would appreciate any help with this.

[ebaines]

I'm not following your description. How big is this "notch?" A couple of days after the full moon there is indeed a shadow on the dark side of the terminator (the line that separates day from night), which for obseervers in the northern hemisphere is on the upper right portion of the moon's disc. Not sure what extra notch you are seeing, but my guess is that perhaps one of the maria (which are the dark area "seas" on the moon) may blend into the shadow in such as way as to look like an extra notch. See the attached pictures and note how the dark area blends into the terminator along the right edge.

One thing for sure: none of the other bodies you mentioned are responsible - Mars, Venus, comets, etc can not cast a shadow on the moon, and when the earth casts a shadow on the moon it's called a lunar eclipse and does not appear the way you are describing.

[Stratmando]

ebaines, just curious, are you saying Mercury and Venus never cast a shadow on our moon, or we just can't see it as it would be on the other side of the moon, or if it was in a position to see, the sun would be too bright?

[ebaines]

Hi Stratmando: An object can cast a shadow only of its apparent size is equal to or larger than the source of illumination. Thus the moon can cast a shadow on the earth because it is 1/400 the diameter of the sun and also 1/400 the distance from the earth as the sun. So as seen from the earth they are both the same apparent size. What we see in a solar eclipse is the moon covering the sun, and it can cast a narrow shadow on the earth during a solar eclipse. But objects much further away - like Venus - have an apparent diameter that is too small compared to the sun to cast a shadow on the earth or moon. Instead what we see is a small disc of the planet in front of a much larger disc of the sun. I've attached an image of Venus crossing in front of the sun to illustrate this.

[Stratmando]

Thanks for shining light on the subject. I understand now, Would have figured it if I thought a little more. Thanks again.