Sky & Telescope - July 2020 - 6

FROM OUR READERS
Resolving Power

Stars in the City

Ken Pilon captured this image of
the January 2019 lunar eclipse
from his ninth-ﬂoor city balcony.

Ken Pilon's Focal Point (S&T: Feb. 2020, p. 84) surprised me. There were no examples of the purported good images taken from his ninth-ﬂoor city balcony. There
wasn't even a link to a website with his images. I sure would have liked to see some.
Richard Lighthill * La Pine, Oregon

Ken Pilon replies: I am so glad that you want to see a few of my photos. I just
completed a new website on the very same subject, astro-imaging from an urban
balcony, https://is.gd/thewhitezone.

I found Ken Pilon's article fascinating and encouraging. For years, I have been
observing from the driveway of my townhouse complex. The only semi-dark skies
available are in the north and west. But I made it work using the same techniques
as Ken, particularly selecting star clusters for most of my imaging objects.
Then, in December of 2018, I started using the observatory at Garvey Ranch
Park, located in very urban Monterey Park, right next to Los Angeles. It allows our
club members to observe every Wednesday night, weather permitting. The ease of
use of the facility, particularly no equipment setup, increases observing time. However, there is an athletic ﬁeld right next to the observatory with lots of ﬂoodlights.
The more I observe the more I see, and as long as I keep my expectations reasonable, I can see a lot!
Dave Nakamoto * Azusa, California

Jack and the Moon Giants
The letter from Jim Michnowicz (S&T:
Feb. 2020, p. 6) noted his observation of
a "Lunar Tiki God" near the Fra Mauro
region of the Moon. As he mentions, this
is an example of pareidolia - the tendency to perceive a recognizable object in
a visually ambiguous image.
Many others have reported such
Moon illusions, but the undisputed
"King of Lunar Pareidolia" is Jack P.
Swaney. During the early 1980s, in
a series of letters to Fate magazine,
Swaney reported detecting dozens of
huge, artiﬁcial structures on the Moon
using his amateur telescope. They reveal
6

J U LY 2 0 2 0 * S K Y & T E L E S C O P E

a bewildering assortment of objects,
including a construction crane, a bridge,
a pipe, and even a kewpie doll.
One of my favorite observing
projects is to examine these "Swaney
Objects" with my 8-inch SchmidtCassegrain. After years of careful
telescopic scrutiny, I can't ﬁnd any
convincing evidence for the existence
of any of them. Either Swaney has a
more active imagination than I do, or
extraterrestrials have secretly removed
these objects to eliminate all evidence
of an alien presence on the Moon.
Frank Ridolfo
Bloomﬁeld, Connecticut

Robert Dick (S&T: Feb. 2020, p. 8)
points out that our eyes have better
horizontal resolution than vertical resolution. I ﬁrst noticed this when I found
that I could see a sailplane towline
in the sky when it was well below the
resolution limit computed by standard
telescope equations using my eye's lens
as the objective's size. Subsequently, I
read that our eyes wiggle horizontally
all the time. While normally this is too
small to detect, I had an acquaintance
with vision so poor I could see his eyes
wiggling back and forth.
If one imagines an image projected
on a grid of sensors, be they pixels or
cells in the eye, and further imagines
moving the image by tiny amounts,
greater detail can be inferred by which
sensors turn on and off. The eye-brain
system does this in real time.
There might be an application of
the mirror-movement systems that
currently combat air turbulence to a
new kind of telescope that increases
resolution by wiggling the objective
and measuring the effects on an image
sensor. For example, this could increase
a space telescope's resolving power
without a larger objective.
Tom Wright
San Diego, California

Sabrina Garvin replies: Accord-

ing to adaptive optics lab director
Donald Gavel (University of California, Santa
Cruz), this method, known as Drizzling, is
often used by the Hubble Space Telescope.
Hubble imagers move the telescope by
a fraction of a pixel to gain more spatial
information about an object. Astronomers
originally developed the technique to help
create the Hubble Deep Field images.

Driveway Spectrum
I was very interested in Jerry Oltion's
article (S&T: Feb. 2020, p. 32) regarding a simple reﬂection spectrograph. A
few years ago, I did a similar experiment
with a cheap 1,500-line-per-inch Hilger
& Watts diffraction grating placed in
front of a 100-mm lens on my DSLR
camera, which I pointed down at the
solar reﬂection off a sewing needle.

https://www.is.gd/thewhitezone

Sky & Telescope - July 2020

Table of Contents for the Digital Edition of Sky & Telescope - July 2020