SKY_September2014.pdf

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

Hα

Measured

Hα

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