A Straight Line on the Moon

[DaveP]

I take photos of the Moon semi-regularly, with just an APSC DSLR and only 420mm of lens focal length to play with. Early this morning as I was preparing to leave my night job, I noticed that the clouds had parted and a nice Moon was out, fairly low in the sky. So, I quickly prepared my camera, but didn't have time to use a tripod and decided just to take some hand-held shots (so, sorry about the quality). Immediately upon looking through the viewfinder, I noticed this anomaly: a dark, straight line on the Southern end. I've never noticed it before, and I knew it was not something in the camera. It remained for several minutes until clouds once again obscured the Moon. This gave me time to grab an OK shot, but somewhat under-exposed. So... what is it???
OK, so I can't seem to find a way to post the image. Here is a link to it on Flicker, if the admins will allow:


-Dave

 

[ChrisA]

You are going to have to put a red circle around your "straight line". I do notice a shadow that appears straight because of the angle.

Remember that any future near the limb is seen nearly edge-on. Even a perfect circle seen edge-on looks like a very elongated eclipse. Could it be that you are seeing a shadow-filled eclipse?

To explore this you need to use software to process the image to appear as seen from directly overhead, to project the eclipse back into a circle. then see if it is still straight.

 

[COLGeek]

Angle of shadow from a crater. Nothing else.