SOLAR PHOTOGRAPHY OCCLUDER RIG
» 1¾"× 5" steel
mending plates ( 3)
» #6-32 screws ( 6)
» #6-32 nuts ( 8)
» ¼- 20 bolt
» 1" threaded rod
» Wood ball slightly
larger than the diameter of the camera’s
lens Found at craft or
hobby stores, wood
balls may come with
or without a hole
bored partway or
» Black ink or paint
A black marker pen
» Drill and drill bits
Join 2 of the mending plates end-to-end with
three 6-32 screws and nuts, as shown in the photo
above. (You may need to slightly enlarge the holes
in the mending plates.) Drill out the center hole near
the end of the third plate to ¼" diameter, to accept
the ¼- 20 bolt that will secure the camera. Bend the
third plate twice as shown above and fasten it to the
center of one of the 2 base plates with 3 more 6-32
screws and nuts.
Next, determine how high the wood ball needs to
be so that it’s in line with the camera lens. Mount
your camera atop the bent plate with the ¼- 20 bolt.
Hand-tighten the bolt to avoid damaging the camera;
if it’s loose, insert a few washers to take up the slack.
Now measure the distance from the base plates to
the center of the lens. Add to this distance 1" plus
half the diameter of the wood ball. Use a hacksaw to
cut the threaded rod to this length.
Twist the cut end of the rod into the wood ball.
Turn a 6-32 nut onto the uncut end of the rod until
it’s about 1" from the end. Remove the camera and
set it aside. Insert the end of the rod through the
center hole in the end of the base plate opposite the
camera mount and secure it with another 6-32 nut.
Complete the occluder by coating the ball and the
threaded rod with black paint or ink.
29 Jun 2008. African dust. Sunlight
transmission at 525 nm (green): 60.1%
08 Oct 2008. Clear sky. Sunlight
transmission at 525 nm (green): 94.3%
Photography by Forrest M. Mims III
TOP: The author’s
Canon G9 mounted on
a simple occluder platform that blocks direct
sunlight from entering
the camera lens.
BOTTOM: The solar
from South Texas on
a day with thick dust
from the Sahara (left)
and a very clear day
(right). Both images
confirm the Naval
Research Lab’s aerosol
forecasts for the same
days ( nrlmry.navy.mil/