Sky and Telescope - June 2015 - 40

Solargraphy
To record your own
solargraph, you'll need
a thin metal can or
other waterproof container that can be sealed
from extraneous light,
black-and-white photographic paper, a pin
or needle, scissors,
a nail ﬁle, and black electrical tape.
The most important part
of your pinhole camera
is the pinhole aperture.
Place it in the middle of
your can, but be careful
not to make the hole
too big or else it will let
in too much sunlight
and overexpose your
solargraph.
When inserting your
photographic paper, be
careful not to expose it
to direct sunlight, and
make sure its emulsion side is facing your
pinhole aperture. Secure
the paper to the inside
of your camera on its
four corners with small
pieces of tape.
Seal the end of the can
tightly with several
layers of tape to ensure
that no extraneous light
gets into your pinhole
camera. Also be sure
to cover the pinhole
aperture with a piece of
tape until you're ready
to begin the solargraph
exposure.

you'll need to assemble your pinhole camera. This may
be an aluminum beverage can or any other light-tight
and weatherproof container. You'll need to be able to
open and close the camera, so if you use a can, expand
the opening using a can opener or a knife.
The next step is to make a tiny pinhole measuring 1
millimeter or smaller using a needle. The smaller the
pinhole, the sharper the image produced and the longer
you can expose your paper before overexposure, or "fogging" becomes a problem. The goal is to be able to take
the longest exposure possible. Poking the hole from the
inside of your can will allow you to easily ﬁ le oﬀ any
burrs, which will reduce vignetting in your ﬁnal image.
Now that you have the pinhole camera ready to go,
you'll need a sheet of photographic paper. You can ﬁnd
photo paper in photography stores, and many sources
are available online. Although any brand can be used,
the key is to use black-and-white photographic paper,
which contains silver compounds that break down in the
presence of light. Color photographic paper contains different compounds that do not react in the same way. In
fact, black-and-white photographic paper will still work
for solargraphy even if it's beyond its marked expiration
date (and therefore cheaper).
Loading the paper into the camera doesn't have to be
done in total darkness, but it's important not to expose
the paper to direct sunlight. Perhaps the best method is
to insert the paper by the light of a single dim bulb in
the opposite corner of a room. Make sure to insert the
paper with the light-sensitive side (the emulsion) facing
the pinhole. Tape the corners to the inside of the can, to
ensure changes in temperature or humidity won't curl
the paper during its long exposure. Finally, close the
can tightly using black insulation tape, to ensure that
no other light enters into the can except through the
pinhole aperture. Finally, cover the pinhole with a small
piece of black tape as well.

Caution Before Exposing
Now your solargraph is ready to use. But before setting
it up for its long exposure, it is crucial that if you plan to
place your camera in a public location, you ﬁrst attain
any necessary permissions from property owners or local
authorities. In early February, a pinhole camera aﬃ xed to
a bridge in downtown Atlanta, Georgia, caused a major
disruption that required disposal by a bomb squad!
Choose a spot where the camera will remain
untouched throughout the entire planned exposure
time. Aﬃ xing it to a stable structure is a good idea: you
can attach the camera to a balcony, pole, railing, or tree.
Securely mount your pinhole camera so that it doesn't move
at all during its half-year exposure. Also be sure to attain
permission from the local authorities before mounting your
camera in a public location.

June 2015 sky & telescope

Sky and Telescope - June 2015

Table of Contents for the Digital Edition of Sky and Telescope - June 2015