Re: Stereo photos of the moon

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

I tried to take stereo photos of the moon several years ago, with
unsatisfactory results. Several factors:
 - I tried the "Earth rotation" method. As a result, I needed to try it
    when the moon was full or near-full, for two reasons:
     1) Near full moon is the only time of the month that the moon is
         up and in a dark sky for most of the night.
     2) If the terminator (day-night line) were visible, it would move
         enough over the course of a night to be visibly different on the
         two photos.
   But the best moon photos are usually taken when the terminator is visible
    (moon only partially full), because the side lighting highlights the
    craters. The full moon does have visible features, however.
 - Those good stereo photos that have been taken with intervals of months
    or years between the shots involve *extremely* complicated calculations
    to get the moon in favorable positions *and* the terminator in the same
    place in the two shots.
 - I used a telescope to get my moon photos to pretty much fill the field
    of view. But the magnification distorted the stereo effect very badly.
    If you don't magnify at all, you may get good 3D, but it would be
    comparable to the 3D you see in a marble held at arm's length.
    A moderate amount of magnification may be acceptable. (This seems to
    be one of those cases where creating a computer model and using it
    to change the perspective would be helpful.)

John R

PS - regarding features on the sun - we're currently somewhere near the
11-year solar minimum, which means fewer sunspots than usual. I got some
good sunspot photos several years ago using equipment designed for the
purpose, but again the high magnification I used caused problems in
producing a stereo pair.


------------------------------