Aldrin versus Armstrong in AS11-40-5903. I see the problem; it's my fault.

Aldrin is the subject of the photo, but Armstrong appears in it in the visor reflection. The problem is that there are two hot-spots in this photo: one behind Aldrin and likely caused by the reflection from facets of the LM, and one associated with Armstrong and very clearly due to heiligenschien. We have to be certain which pool of light we're talking about from moment to moment.

Anticipating Mr. Cosnette's typical, "But which is it? You can't seem to agree!" let me be as explicit as possible.

The pool of light behind Aldrin is most likely the somewhat directional reflection of light from the cover of the LM's aft equipment bay. That is the most likely LM surface to provide such a reflection. Obviously an object like the lunar module with many facets facing odd directions will present a number of opportunities for partially directional reflections.

If we closely examine the reflection in Aldrin's visor, we see the reflection of Armstrong taking the picture. And in the reflection of the lunar surface behind the reflection of Armstrong we see another pool of light. Reflection establishes a new line of sight. The image in the visor is produced by the line(s) of sight which extend from there to objects and surfaces in front of Aldrin, and probably behind the photographer.

When the light of sight corresponds to the angle at which light strikes the object, we say scientifically that the phase angle is zero. And some peculiar things happen when the phase angle is zero. Specifically, objects obscure their own shadows.

I've already posted photos taken on earth which show this phenomenon. It can be seen on earth, typically any time you have a broad expanse of textured surface. I recently saw some film taken from one of those hydrogen peroxide rocket packs which showed the pilot's shadow on a grassy field. Heiligenschein was clearly apparent. There is also a down-sun shot from the film Apocalypse Now in which helicopters are flying over the jungle canopy and heiligenschein is very noticeable around the copter's shadow. It can be seen on earth, but it's harsher on the lunar surface where shadows are harsher.

It's quite important to realize that it's solely a function of phase angle, or the difference between the line of sight and the direction of illumination. If I were standing on the lunar surface taking a picture of my own shadow, I would see a very strong heiligenschein surrounding the "head" of my shadow. But if my companion astronaut were standing off to the side and looking at the tip of my shadow from a different angle, he wouldn't see it.

The hot spot reflected in the visor is actually the easiest to explain. And despite what Mr. Lundberg thinks, it's not a spot light.


<font size=-1>[ This Message was edited by: JayUtah on 2002-06-29 17:52 ]</font>