Venus over the Apollo 14 LM
Copyright © 2007 by Danny
Ross Lunsford and Eric
All rights reserved.
Last revised 17 August 2009.
Scans of the images taken on the moon sometimes show star-like spots
due to dust on the film or other causes.
don't appear in separate
frames of the same celestial location (see below). The fact that
star-like object shows up in both frames at the same location relative
to the crescent Earth strongly indicates that it is a real celestial
object. The fact that it also appears in the same relative
location in the other seven frames in the series is compelling evidence
that it is either a planet or a very bright star. Note that
Charlie Duke also photographed Venus, capturing it in three frames of his
Apollo 16 Station 10 Prime panorama.
Enhanced versions of two of a series of nine photos of Earth -
AS14-64-9189 to 9197 -
Al Shepard took of Earth over the LM at 135:03:42 while
waiting for CapCom
Fred Haise to get an answer from the Backroom.
Software such as Starry Night or Celestia let us see what the sky was
like at the Fra Mauro landing site at the time Shepard took the photos,
which was about 1207 GMT/UTC on 6 February 1971. A quick look
shows that Venus was in the right relative location. At that time
and on the airless Moon, Venus had an apparent magntiude of about
-4.1. Only the Sun and Earth were brighter. The next
brightest object visible at that time was Jupiter, with a magnitude of
-2.0 but eight degrees west of the zenith and well out of the
field-of-view. Even if it had been in view, it would have been 7
times fainter than Venus and, because of the short exposure times,
might not have registered on the film.
This comparison has a negative (reverse) detail from AS14-64-9191
on the right and a negative detail of Venus and the Earth from Starry
Night. The latter has been rotated and scaled to match the
mission photo. An overlay of the two images is shown at the
center. Note that we are able to match both the separation
between Venus and the Earth and the Earth's size, which further
confirms that the star-like object is Venus.
Even though Venus's angular diameter as
seen from the Moon was only 21 arc seconds - about 1/325th of Earth's
- it has the same surface brightness it would have if we were
right on top of it, because of the inverse square law of light
propagation. Because Venus is covered with clouds, and closer to the
Sun, its surface brightness is roughly twice that of Earth.
Consequently, an exposure that gets the Earth right, will also
necessarily show Venus. This is why you can see Venus in broad daylight
if you know exactly where to look - and can manage the trick of
focusing at infinity when confronted with an otherwise featureless
As mentioned above, Venus is
present in all nine of the images in Al Shepard's sequence of Earth
photos. In many of the images, we can also see bright spots
which, because they don't repeat from frame to frame, are undoubtedly
due to dust on the film or on the scanner, or some other cause
unrelated to what was actually in the sky over Fra Mauro. In the
following film strip, the details from the mission photos are presented
at the same scale and with the same brightness enhancement (255 levels
reduced to 50). For ease of comparison, an L-shaped figure was
drawn from the detail of AS14-64-9192 with the longer line connecting
the horns of the crescent Earth and the shorter line pointing at
Venus. The L-shaped figure was then superimposed on each of the
other frame details after a rotation needed to put the figure into same
orientation relative to the crescent and to Venus. No scaling was
done. Rotation of the L-shaped figure is necessary because
Shepard took the photos while holding onto the LM ladder, leaning back,
and holding the camera in his hand. As can be seen in the film
strip, he was in much the same position while taking each of the first
five photos but then leaned to his right - moving Venus away from the
rendezvous radar antenna - for the last four photos. Possibly he
saw Venus and shifted to his right to ensure that he captured it in at
least the last four images. We don't
know if he changed f-stops, but all the frames were undoubtedly taken
at 1/250th of a second.
Animated gif by Yuri Krasilnikov,
after a similar animation posted
by 'Data Cable'.
Details from the nine frames taken by Al Shepard at about 1207
GMT/UT on 6 February 1971. The L-shaped figure was constructed as
an overlay to 9192 with the long line connecting the horns of the
crescent Earth and the short line pointing at Venus. The L-shaped
figure was then superimposed on the details from the other frames after
a rotation to reproduce the positon of the figure relative to the
crescent Earth and Venus. No scaling was done. Note the
various star-like spots, particularly in the later frames.