Crepuscular Moon Rays Over Thurso Castle (APOD 2009 May 18)

[Chris Peterson]

I'm thinking that the magnitude -27 sun produces magnitude -2 to -7 crepuscular rays (depending on the "misting factor")
so a magnitude -13 full moon should produce magnitude +12 to +7 crepuscular rays.

The Thurso Castle "crepuscular rays" look a lot brighter than that!

Well, if the rays are the shadows, there's no problem. Keep in mind that people regularly make nighttime images under moonlight using 30-60 second exposures, and these are indistinguishable from daytime shots.

[neufer]

I'm thinking that the magnitude -27 sun produces magnitude -2 to -7 crepuscular rays (depending on the "misting factor")
so a magnitude -13 full moon should produce magnitude +12 to +7 crepuscular rays.

The Thurso Castle "crepuscular rays" look a lot brighter than that!

Well, if the rays are the shadows, there's no problem. Keep in mind that people regularly make nighttime images under moonlight using 30-60 second exposures, and these are indistinguishable from daytime shots.

Well, if the"lunar crepuscular rays" are MOVING shadows, there IS a problem.
Clouds, including the one that you assume covers the April 8 moon,
often move quite a bit over a period of 30-60 seconds.

(Perhaps the periodic clouds that are generating the periodic
"lunar crepuscular rays" on the left are due to standing mountain wave clouds.)

Besides, if longer exposures, faster film & shorter f-stops are turning the full moon
into a 400,000 times brighter (effective) sun then why is the sky so darn dark?

I recommend that this APOD gets renamed "Moon Rays Over Thurso Castle?"
and have APOD members queried as to what they think we are seeing.