On 8/18/2017 6:29 PM, Davoud wrote:
Ken Hart:
I would think you would need more than one flash. Remember, the light
diminishes as the square of the distance...

Right. But you won't need a flash at all to photograph details on the
near side. The geometry will be such that the near side will be fully
illuminated by reflected earthlight. My imaging partner plans to
photograph the Moon in that fashion, no doubt overexposing the solar
corona by a certain amount. Should be a beautiful photo.


Indeed. The concept sounds neat. Depending on the length of the
exposure, HDR might work.
For long exposures of sunsets,or sunrises, I have placed my hand, or
other opaque object, near the top of the lens to hold back exposure in
that area. Your shooting partner might want to try cutting a hold in the
cardboard. It works something like a graduated filter, but I don't have
the drawback of an extra surface.

--
PeterN