OP --

According to the surface journals, At the same time that picture of Buzz Aldrin was being taken (the one in the OP), Buzz was setting up the solar wind experiment (that mast and panel in front of him) and saying this:

110:03:36 Aldrin:
And, incidentally, you can use the shadow that the staff makes to assist you getting it perpendicular (to the Sun line)

So it is possible he was pointing at the shadow made by the solar wind experiment, which would coincide with the discussion he was having with the people at Houston. According to Armstrong's log, he took two images about the time Aldrin was talking about the solar wind experiment, this image being one of them.