Sky & Telescope - February 2020 - 84

FOCAL POINT by Ken Pilon

You might be surprised at all the
advantages over a dark-sky site.
THE NIGHT SKY IS NOW CLEAR and

dark. With a limiting magnitude of
3.5, it's a good night. I set up the telescope for some deep-sky imaging.
My site is not ideal. I'm imaging
from my 9th-ﬂoor, northwest-facing
balcony in heavy light pollution amidst
Toronto's population of ﬁve million.
Having no convenient access to a dark
sky, I work with what I have. Other
amateurs who live in cities might not
even try urban astronomy, ﬁguring
what's the point.
I used to observe in the usual way,
eyeball to eyepiece, using my 20-cm
Schmidt-Cass Go To telescope. Finding
targets in a washed-out sky proved
difﬁcult, but I didn't give up. I wanted
more. So I set the eyepieces aside and
invested in an astronomical camera
and a laptop. I then learned the best
targets to image with my equipment
and light-polluted skies without using
ﬁlters. It changed everything.
Monochrome CCD/CMOS sensors are about three times faster than

84

FEBRUARY 2 02 0 * SK Y & TELESCOPE

and rigid. Equipment theft is not an
issue, so my suitably protected telescope and equipment can stay on the
balcony year-round.
Lastly, observing from a dark-sky
site can involve costs for gas, vacation
time, even hotels and restaurants. A
balcony site's cost is effectively zero
every time. I also know when it's clear
for each balcony observing session.
This contrasts with a distant dark-sky
site, which might have clouded over
by the time you reach it, or, worse,
remains cloudy throughout your
expensive cottage rental period. Ouch!
They say the best telescope to buy is
the one you'll actually use. Well, the
same is true for observing sites! This
city astronomer can now smile.
¢ KEN PILON, an urban astronomer
for more than half a century, is a former
editor of 'Scope, the newsletter of the
Royal Astronomical Society of Canada's
Toronto Center.

VA LLE YBOI 6 3 / SHUT TERSTOCK .COM

Imaging
Nine
Floors Up

color cameras. They also have a wide
spectral response that includes stellar
wavelengths not produced by artiﬁcial
lighting. Taking multiple exposures of
1 to 10 seconds each, totaling 10 to 20
minutes, reduces any tracking issues.
Software then removes ﬁeld rotation
and sky brightness while at the same
time enhancing my targets.
I can now image faint magnitudes.
The telescope's limiting magnitude
went from 12.5 visually to 15.5 on the
live-image laptop and, after processing, to 18 with the full Moon and
greater than 19 when moonless. My
observing sessions are now longer, and
they go much deeper into space. I've
gained 7 magnitudes by switching to
mono-imaging and lose just 1.3 magnitudes compared to a dark-sky site.
I have discovered many advantages
of a balcony over a distant dark-sky
location. Travel time from home to
observing site is only seconds, and my
set-up time is under 15 minutes. Nine
ﬂoors up means no dew or mosquitoes,
ever. I can "observe" from my living
room, and, barring a blackout, I'll
never run out of power. Maintaining
dark adaptation is unnecessary, and I
can easily see my way around the balcony site. Forgetting to bring critical
items to a distant viewing site can be
a big deal. With the balcony, I simply
step inside to retrieve them.
A balcony also has full site security. No strangers, curiosity seekers,
animals, property owners, or police
with ﬂashlights will ever show up. The
balcony's concrete ﬂoor is ﬂat, hard,
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Sky & Telescope - February 2020

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