Proposal: Self-portrait with telescope (via the moon)

The concept

An image taken through a telescope pointed at the retroreflectors on the moon. The image in principle then consists of a photograph in a mirror of the photographer with the telescope.

Whether this makes a compelling image is in the eye of the beholder, but it is only of significance if the technique for taking the photograph is known.

Simulated image below (yes, it just looks like one pixel)

selfportraitwithtelescope

The science

Retroreflectors bounce light back along the incident path so act like a plane mirror but from all angles and with the image flipped. The Apollo 11, 14, and 15 missions left sets of retroreflectors on the moon for the Lunar Laser Ranging Experiment, as did some Russian missions.

Hence a photograph taken of the retroreflectors will include the camera centered in the frame of the image.

The real challenge is that not enough light travels from the telescope to the moon and back to the telescope to create a strong image. In fact, the lunar laser ranging experiments point a high-powered laser at the moon. By the time the laser beam reaches the moon is it approximately 6.5 km wide and only about 1 in 10^17 photons originating in each laser pulse return to the laser every few seconds.

The portrait

Because the amount of light returned is minimal, it is only through luck that an actual photon would return in the duration of any particular exposure. If a single photon were returned, the best you could do to reconstruct an image is a single dot on the frame of the camera film/CCD and the color would be close to the color of light reflected from the telescope in the first place. Hence the image would be almost entirely black but with one dot of light at some random point on the film.

 

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