Sky and Telescope - April 2015 - 10

Letters
they're near the zenith and show really nice
crescents as they pass between Earth and
the Sun. A brilliant white Venus or Sirius
against a deep blue sky is a sight to see.
Dave Partyka
Oberlin, Ohio
In his article on daytime astronomy,
Dalla Piazza's comment on "pushing the
envelope" by using doubles to ﬁnd fainter
stars in the daytime took me back to the
early 1990s. I had purchased a Celestron
Classic 8. Although not a Go To scope, it
had adequate setting circles and a Vernier
scale on the right ascension circle, which
enabled me to quickly locate an object in
the night sky. That being so easy, I started
looking for planets and bright stars in the
daytime and eventually got curious about
ﬁnding a personal best.
I was surprised to ﬁnd that I could see
a star as faint as magnitude 6.8 while the
Sun was still above the horizon. Starting
with Arcturus (14 h 15m 39.6 s +19° 10′ 57″),
°
I slewed east to Xi Bootis (14 h 51m 23.2 s)

75, 50 & 25 Years Ago

Don't Skimp on Print
I just wanted to comment on your use in
the print magazine of weblinks to "online
extras," which leaves behind thousands of
inmates such as me. Not all readers have
internet available, and we truly rely on snail
mail as our only access to outside contact.
As extremely important as the internet is
in today's technological society, assuming
readers can go online cuts both prisoners
and other "oﬄine" readers out of the loop
and makes us feel isolated, that people have

April 2015 sky & telescope

forgotten that we exist. There are about 500
inmates here. Snail mail is my only connection with the outside world.
Mail call. I scan the magazine and then
pass it along, to make sure that all get to
experience the privilege of reading S&T.
Steven Lewis, #133282
Randall L. Williams Correctional
Facility, Pine Bluﬀ, Arkansas

For the Record
✹The Atmospheric Dispersion Corrector
(S&T: Jan. 2015, p. 33) is manufactured by
Astro Systems Holland, not Pierro-Astro,
and is available at www.astrosystems.nl.
✹In the February 2015 Deep-Sky Wonders
column, there are two image errors: (1) Abell
24 is north of Zeta Canis Minoris, not Zeta
Canis Majoris as shown in the chart on page
56; (2) on page 58, Douglas's Triangle is not
the three stars in the middle of the image but
the three stars that combine to create the top
"star" in that triangle. A zoomed-in image of
the triangle and a corrected chart appear on
http://is.gd/errata2015.

Roger W. Sinnott

April 1940
Wayward Neptune "[Recently] I computed the
motion of Neptune by Cowell's method, step by
step, from 1780 to 1938. [The] attractions by the
other planets [I evaluated] with the aid of the
Hollerith machines of the Watson Astronomical
Computing Bureau at Columbia University. . . .
"[Neptune's ecliptic] latitudes since 1846
could not possibly be represented by an orbit in
which Pluto's attraction was omitted. . . . The
mass of Pluto found by this determination is
¼00,000 of the sun's mass. This practically equals
the mass of Venus, and is about 82 per cent of
the mass of the earth."
Dirk Brouwer (Yale University Observatory)
pioneered the use of punch-card tabulating
machines before the advent of modern computers.
But in the 1980s astronomers realized Pluto was
too puny to tug noticeably
on Neptune, sparking
speculation that another
Planet X, an unseen dwarf
star nicknamed Nemesis,
or even the attraction of
the Milky Way's center
was involved. Today most

after getting a good focus on Arcturus.
The double Xi Boo is roughly 6′ lower
in declination, so no declination adjustment was necessary. Xi Boo's companion
is a 6.8-magnitude star 5.7′′ from the
primary. The pair is high in the sky just
before sunset in early July. With today's
Go To scopes, this is no longer as great a
challenge, but some readers might want to
give it a try this summer.
Jim McCormick
Victor, Idaho

dynamicists believe small errors in Neptune's
observed position before 1911 created the illusion
of the additional gravitational force.
April 1965
Damon Cameras "A new photographic sky
patrol program has been started at Harvard
Observatory with modern cameras. This is
a revival, on a greatly modiﬁed plan, of the
famous sky patrol that Harvard director E. C.
Pickering began nearly 80 years ago. . . .
"The clear aperture of the Damon lenses is
1.71 inches, corresponding to f/8.1. The useful
ﬁeld on 8-by-10 plates is 30 by 40 degrees. [The]
size of the circle that contains 80 percent of the
light of a star image is 15 microns on the optical axis, and 20 at the edge of the ﬁeld. . . . We
wanted a rugged camera
needing little maintenance, rigid and stable
enough to keep its overall alignment [and] make
unguided exposures of
up to two hours."
Hector C. Ingrao's
article is a classic for its
nuts-and-bolts details of

the Damon patrol cameras, in use through 1989.
The cameras contributed 12,381 astronomical
plates to Harvard's vast collection. Numbering
a half million, the plates are now being digitized
as a resource for future research (more in next
month's issue).
April 1990
Mini Hubbles "[I'm not saying] it was a mistake
to build the Hubble Space Telescope at all. [But]
it was a mistake to sell HST to Congress and to
the public as the space telescope for the rest of
the 20th century. It was a mistake to push HST
ahead of more modest space telescopes that
could have been ﬂying earlier. If we had even
one imaging telescope in the 1-meter class,
looking at the sky with 0.1-arc-second resolution, many of the discoveries that HST will make
might have been made
10 years sooner."
On the eve of the
space telescope's launch,
Freeman J. Dyson (Institute for Advanced Study)
was oﬀering his perspective on HST.

http://www.astrosystems.nl http://www.is.gd/errata2015

Sky and Telescope - April 2015

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