Sky & Telescope - December 2022 - 6

GREG CISKO
FROM OUR READERS
Deep-Sky Imaging with Sequator
I read Sean Walker's Test Report " Nightscaping with Sequator " (S&T: Aug. 2022,
p. 66) with great interest. I have been using Sequator for many years because of its
ease of use and great results.
I've used Sequator for the quick exposures mentioned in the article for nightscapes.
But to my surprise, I found Sequator also works well for images of deepsky
objects with longer exposures, by stacking a great number of subexposures to
create the image.
I took the image of M51 at left on June 28, 2022, using a Sony α7 camera and
Astro-Tech 72-mm ED refractor on a Star Adventurer mount. The total image integration
time was 74 minutes and contains 150 subexposures, each 30 seconds long
with 20 dark frames. I stacked them all in Sequator and adjusted it in Photoshop.
Greg Cisko * St. Charles, Illinois
The Hunt for
Technosignatures
As a member of the board at the SETI
Institute, I just wanted to congratulate
and thank Jeff Hecht for the superb
article " SETI's Big Boost " (S&T: Aug.
2022, p. 34). Hecht captures both the
excitement and the challenges of the
new work effectively for the lay reader.
This article is now my go-to place
for explaining what is happening in
the field to students and anyone who
is interested in the Search for Extraterrestrial
Intelligence. I have shared the
article with all our board members and
will also include a reference to it in the
online textbook I write for OpenStax
(https://is.gd/OpenStaxSETI).
Andrew Fraknoi
San Francisco, California
I read with great interest the latest
update on SETI. However, I would like
to offer a different approach: Instead of
listening for a signal from outer space,
why not generate our own? What if we
sent laser light beams out in a shotgun
approach to different points in the sky?
Based on the speed of light, it might
take hundreds of years to get to some
locations, but at least it could be said
that we are trying to reach out beyond
our own planet.
All the research now seems to
be focused on attempting to receive
random signals from somewhere. I
think the search for extraterrestrial life
should, in part, focus on generating
our own signals.
6
DECEMBER 2022 * SKY & TELESCOPE
It can be argued that those Earth
signals already exist from the early
1900s in AM radio signals and from
the 1950s' first television signals. Some
of those signals did in fact leak out
into our solar system, but not in an
organized fashion.
One problem with this argument is
the inverse square distance law - or
the further a radio or light wave travels
the weaker and wider it becomes.
Signals designed for Earth communications
back when radio and television
were new were never meant to be
received in outer space. The further
they traveled, the weaker they became.
On the other hand, scientists could
transmit a laser light beam to specific
targets. However, just a beam of light
by itself is not enough. If it were blinking
in such a way to suggest that it
was artificially made, it might at some
future point spark the interest of some
life form from another galaxy to investigate
the location of its origin.
Mike Malloy
Corpus Christi, Texas
I am intrigued by the term technosignature
in Jeff Hecht's article on SETI.
It seems rooted in the assumption that
an intelligent species would necessarily
develop technologies capable of
being detected over many light-years.
The examples Hecht gives strike me
as extrapolations of human technologies
that have existed for 100 years or
less - a vanishingly brief period in the
history of our species.
Humans have demonstrated their
intelligence in astonishingly diverse
ways over the past 150,000 years. The
peoples who created such artifacts as
the Mayan calendar, Chinese calligraphy,
and the bronze sculptures of IgboUkwu
were assuredly as intelligent as
contemporary scientists. Could their
technologies have generated the sorts
of technosignatures sought by SETI?
The questions asked by scientists
often reflect biases of their own culture.
For example, as noted in S&T's
July 2018 issue, the terrestrial " Canal
Mania " of Percival Lowell's day may
have shaped his observations of the
purported canals on Mars. Are the
" extraterrestrial " artifacts contemporary
SETI scientists seek perhaps only
reflections of ourselves?
Thomas Whitman
Philadelphia, Pennsylvania
Thanks for the Laugh
Last night, I was reading August's S&T
and started laughing out loud. To be
sure, I have never previously laughed
out loud at anything in S&T. (My wife
thought I'd finally lost it.)
I was reading Fred Ringwald's
letter ( " Comet IRAS-Araki-Alcock, "
S&T: Aug. 2022, p. 6), in which he
was tempted to point callers to Venus
instead of the comet. I can understand
his frustration and his temptation, but
kudos to him for being honest!
I recently was asked to help find
" Dave's Star. " My friend Dave had been
given one of those " official star named
https://www.is.gd/OpenStaxSETI
Sky & Telescope - December 2022

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