Sky & Telescope - February 2024 - 7

Smoking Scope
I read Arwen Rimmer's " The Sun: Now
in High-Def " (S&T: Nov. 2023, p. 14)
with interest, including the admonition
regarding the danger of concentrated
sunlight to both observer and scope.
On a recent Sunday, I rolled my
13-inch Dobsonian off the back lawn to
run the sprinklers. I parked it in a safe
spot, poured myself a coffee, and sat on
the patio to enjoy the morning. A few
minutes later, I glanced over at my scope,
and it was smoking! I rushed over and
quickly reangled the scope. Concentrated
light had passed through the 5-inch offaxis
mask and started to burn the ABS
mask material. I covered the burn with
black camera tape, and it's good as new.
I consider myself very lucky. If the
mask had not been on, the full force of
the mirror would have drifted onto the
flat-black plywood of the secondary cage.
Lesson learned.
Bob Gitzen
Concord, California
Living-Room Observing
The " Astronomy for Retirees " letters
(S&T: Oct. 2023, p. 6) from Edward
Daugherty and Benton Kesler in
response to " An Observatory for Seniors "
(S&T: July 2023, p. 84) prompted me to
write about my own reasons for building
a remote-controlled observatory at my
home. My wife has Alzheimer's and can't
be left alone. This negated the pursuit of
many of my hobbies - but not astronomy.
I purchased a NexDome observatory,
which I installed next to my home
(after months of discussion with county
zoning officials). I can now remotely
control my observatory from within my
home and view images on my big-screen
television. I can spend time with my wife
and still do astronomy. Life can be good
even with dementia.
The observatory has also prompted a
great deal of public interest within my
community. People frequently stop by
to see it. I had several reflector telescopes,
which I gave to neighborhood
youth. The observatory has become
quite a conversation piece.
William Johnson
Manassas, Virginia
Cosmic Relief on Hold
David Grinspoon's Cosmic Relief is one
of my favorite columns, and I was sad
to read in " Seeing Through the Smoke "
(S&T: Nov. 2023, p. 11) that he will not
be writing the column for a while. I read
his book Chasing New Horizons [cowritten
with Alan Stern]. It was riveting
throughout. I'm grateful that David
Grinspoon became a columnist with
S&T. Thanks, David, for 14 years of your
creative, thought-provoking articles.
Tom Kellogg
Aptos, California
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letters@skyandtelescope.org. Please limit your comments to 250 words; letters may be edited for brevity and clarity.
75, 50 & 25 YEARS AGO by Roger W. Sinnott
In 1954, Daniel M. Popper mea1949
1974
º
February 1949
Einstein Effect " In the early
1930's, Dr. R. J. Trumpler, of
Lick Observatory, found certain
stars in the sky which showed an
abnormal red shift in the lines of
their spectra. These were all very
hot stars of class O, and it was
proposed that the red shifts were
caused by an Einstein shift - the
effect of gravity retarding the
escape of light from the surfaces
of very dense stars. . . .
" At the Dominion Astrophysical
1999
Observatory, Dr. J. A. Pearce has
made a detailed spectroscopic
analysis of HD 215835, [one such
star in] Cepheus. . . . Dr. Pearce
found double lines, indicating [it is]
a spectroscopic binary. [But the
components'] densities are about
4/100 that of the sun. . . . The estimated
maximum mass of 62 suns
is large, but normal for stars of this
type. . . . The present work does
not support the relativity red-shift
hypothesis for this star. "
sured a true gravitational redshift
in spectra of the white dwarf 40
Eridani B.
º February 1974
Pioneer 10 " Mankind has just
extended its bounds of exploration
by the bold voyage of a probe far
beyond the orbit of Mars for a closeup
examination of Jupiter. . . . The
most striking finding is the exceedingly
strong concentration of the
trapped radiation toward the plane
of the magnetic equator. . . . In
the giant planet's vicinity, Kinard's
meteoroid detector was penetrated
by some 10 particles, fewer than
he had expected . . . If this planet
should have a thin equatorial ring of
particles, like Saturn's rings, it could
not have been detected by any of
the Pioneer experiments, because
of the spacecraft's rapid transit
through such a ring. "
Tom Gehrels's indirect prediction
was borne out five years
later, when Voyager 1 did detect
Jupiter's diaphanous ring.
º February 1999
Unexpected Double " The innermost
Eta Carinae nebula, one of the
most spectacular objects imaged
by the Hubble Space Telescope, is
not what it appears to be.
" We seem to see an extremely
luminous star that has ejected
two massive, smoky lobes of gas
and dust . . . The lobes appear to
have erupted from the star about
150 years ago, when Eta Carinae,
[about 6th-magnitude,] flared to
magnitude -0.8, making it the
second-brightest star in the night
sky . . .
" 'This situation of a nebula that
is chemically more advanced than
the central star cannot be reached
by the evolution of a single star,'
write Henny Lamers [and colleagues].
'The star whose spectrum
now dominates the nucleus was not
the star that ejected the nebula.' . . .
If this unseen second star . . . blew
off the nebula, it presumably began
life with an even greater mass and
luminosity than the star we call Eta
Carinae today. "
sk yand tele scope .o r g * FEBRUARY 2024
7

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