SKY_September2014.pdf

(Axel Boer) #1

Letters


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Call for Orion Observers
After a very successful Epsilon Aurigae
campaign (S&T: Mar. 2012, p. 18), I have
started another astronomical endeavor
called the Orion Project. Initially it began
as a spectroscopic program for Betelgeuse
but has expanded to Rigel, Mintaka,
Alnilam, and Alnitak. Edward Guinan
(Villanova University) and John Martin
(University of Illinois, Springfi eld) have
been watching Betelgeuse for years, and
with their encouragement I’m coordinat-
ing an ongoing spectroscopic and pho-
tometric campaign to amass continuous
observational data for these stars.
Even if you are not experienced or are
just getting into photometry or spectros-
copy, this is a good project to learn from.
The constellation Orion is unique in that
it is easily visible from much of the popu-
lated world. It’s also visible during the fall
and spring seasons, making observing
pleasant. Because the stars are bright,
they’re ideal for spectroscopy, even with
modest telescopes. Photometry presents
just the opposite challenge, because CCD
photometry requires special bright-star
techniques. The SSP-3 and SSP-4 PIN
diode photometers are ideal for this work,
because their decreased sensitivity works
well for the bright stars.
We have several observers from around
the world doing both photometry and
spectroscopy on the project’s fi ve stars.
One interesting thing we’ve found is a
repeating switch in Alnilam’s spectra,
with the hydrogen-alpha line fl ipping
from absorption to emission on the order
of hours to a couple of days. This shift also
appears in professional observations. It
might be due to variability in the stellar
wind emission.

Interested observers will need the
proper equipment and knowhow. Help
and mentoring are available. If you’re
interested, please visit the project website
at http://www.hposoft.com/Orion/Orion.html or
e-mail me at phxjeff @hposoft.com.
Jeff Hopkins
Phoenix, Arizona

Simply Wonderful
James Mullaney makes some valid points
in his article about observing with small
scopes (S&T: Apr. 2014, p. 38). A small
instrument has its place in any observer’s
arsenal. Those wanting to fi ll the gap
between small binoculars and larger tele-
scopes could instead consider a pair of big
binoculars. A pair of 25×100 binoculars
provides more light grasp than Mullaney’s
90-mm spotting scope, as well as a larger
fi eld of view (2.3°° versus 1.7°). This view
allows for terrifi c “big-picture” observ-
ing, allowing you to see star clusters and
nebulae in large, rich fi elds of background
stars. Big binoculars also greatly enhance
the sense of depth perception that Mul-
laney speaks about because the observer is

using both eyes, and most observers will
fi nd better contrast in the image.
Many 80- to 125-mm binoculars can
be purchased at a nominal price. Well-
mounted on a good tripod, big binoculars
are quick to set up for a viewing session.
I’ve spent the last year rediscovering the
Messier objects and observing obscure,
large star clusters that I can see only
poorly in large refl ectors. One class of
object that Mullaney failed to mention is
dark nebulae; dozens of these objects are
beautifully seen in rich Milky Way fi elds
with 25×100 binoculars.
Mark Bratton
Limerick, Saskatchewan

Thank you for Mullaney’s “Stargazing
Simplifi ed.” He reminded many of us of
why we became amateur astronomers in
the fi rst place: to enjoy the spiritual beauty
of the sky.
I can trace my interest back to when I
fi rst saw Sputnik 1 fl y overhead on a bril-
liant October night in 1957. These days,
my most convenient instrument for casual
observing is a pair of 20×80 binoculars

Flux

Flux

February 17–18, 2014
900-second exposure

Spectra for Alnilam (Epsilon Ori)

February 19–20, 2014
600-second exposure

Wavelength (nanometers)

652.5 653.0 653.5 654.0 654.5 655.0 655.5 656.0 656.5 657.0 657.5 658.

Wavelength (nanometers)

652.5 653.0 653.5 654.0 654.5 655.0 655.5 656.0 656.5 657.0 657.5 658.

Telluric lines

Telluric lines

Rest wavelength
of Hα

Rest wavelength
of Hα

Measured

Measured

The central star in Orion’s Belt, Alnilam, has a hydrogen-alpha feature that fl ip-fl ops between being
an absorption and an emission line. Amateur Jeff Hopkins took these spectra with a Meade 12-inch
LX200GPS Schmidt-Cassegrain and Lhires III 2400 spectrograph.

S&T:

LEAH TISCIONE; SOURCE: JEFF HOPKINS

8 September 2014 sky & telescope

Ltte_layout.indd 8 6/23/14 12:18 PM

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