Sky and Telescope - March 2017 - 72

Astronomer's Workbench by Jerry Oltion

Let There Be Light
How to darken your relations with your neighbors.

amateur astronomers' existence. For
many of us, our backyards or driveways
would be great places for observing if
it weren't for those $#@! lights shining at us from all sides. Fortunately the
International Dark Sky Association and
many medical professionals have been
getting the word out that too much
light is not only bad for astronomy but
bad for people's (and animals') health.
That means we have more ammunition
than ever in convincing our neighbors
to let us shield their lights.
And that means we need to be ready
to shield those lights the moment we get
permission. It may seem simple - and it
is - but you don't want to be fumbling
around on your neighbor's front porch
learning how when the time comes. You
want to know exactly what to do and do
it efﬁciently and well. Here's how:
You can always buy a shielded ﬁ xture
and install it. I recommend the Hampton Bay #HB48017MP-237 from Home
Depot, seen on the facing page. It's fully
shielded and has a motion sensor so the
light will stay off until it's needed.
Or you can make a shield yourself

out of galvanized tin. What you want is
to block light from going outward and
upward, while letting it shine downward onto the porch and walkway. The
ﬁrst step, then, is to make sure the
existing ﬁ xture will allow light to shine
down. Many carriage-lantern style ﬁ xtures won't. They're generally too bulky
to shield anyway, so you'll need to buy
a small ﬁ xture that lets the bulb point
downward. Fortunately those are both
common and cheap.
While you're buying the smaller
ﬁ xture, get a length of galvanized tin
about 18 to 22 inches long and 7 to
10 inches high. File the edges smooth
so you don't cut yourself on them. It
will probably already be curved from
being on a roll. Gently adjust the curve
to make a half cylinder out of it. Then
get (or make) some simple right-angle
mounting brackets.
Paint the outside of the shield
whatever color your neighbor prefers,
but leave the inside galvanized so it will
reﬂect light.
Now simply mount the new ﬁ xture (make sure the power is off!) and
install the light bulb. I recommend a

p A carriage-lantern style light, one of the
worst kind for glare. Note that it doesn't shine
downward, where the light is needed most.

40-watt equivalent (7-watt actual) LED
ﬂoodlight. Get the warmest color temperature you can ﬁnd (probably 2700K).
Then install the shield around
the ﬁ xture and bulb. You do that by
screwing the brackets to the wall, then
attaching the shield to the brackets.
It should be positioned to completely
block the bulb from view for anyone
standing more than a few feet away
from it, while letting the downward-

p Left: Replace the carriage light with a downward-facing fixture and a downward-facing flood bulb. Note the brackets for mounting the shield that
are attached to the siding. Middle: Install the brackets on the wall, and then attach the shield (shown assembled). Right: The finished shielded fixture
casts its light downward where it's useful, not outward into your eyepiece.

M A R C H 2 0 1 7 * SK Y & TELESCOPE

JERRY OLTION (4)

OUTDOOR LIGHTS ARE THE BANE of

Sky and Telescope - March 2017

Table of Contents for the Digital Edition of Sky and Telescope - March 2017