Australian Sky & Telescope — July 2017

54 AUSTRALIAN SKY & TELESCOPE July 2017

binoculars, telescopes, or occasionally,

the naked eye (for instance, the Great

Rift stretches more than 120° from

Deneb to Alpha Centauri, offering

one of the largest possible naked-eye

targets). To really dig in to dark nebulae

you’ll need binoculars or a telescope

with a very wide field of view: a

specially designed rich-field telescope or

a scope equipped with one of the newer

wide-field eyepieces. Increasing aperture

increases the size of the nebula through

your eyepiece and improves the contrast

between the nebula and skyglow. But

these ‘improvements’ may not be much

help, as some dark nebulae are so broad

that they’ll stretch beyond your field of

view. For nebulae longer than 1°, you’ll

do better with a small aperture f/3 or

f/4 scope with an 80° or 100° eyepiece

that provides a wider field of view — the

right combination can yield a field of

view as wide as 3°. Low-power, high-

aperture binoculars are also a good

option for hunting these dust clouds.

You’ll also need a dark sky and good

transparency, two conditions that are

sometimes difficult to obtain. Move

away from light pollution (star party,

anyone?) and meticulously protect your

dark-adapted vision.

A different catalogue

Most dark nebulae favoured by amateur

astronomers come from the Barnard

catalogue, compiled by E. E. Barnard

based on photographic plates taken at

Lick Observatory and Mount Wilson

Observatory, or the Lynds catalogue,

compiled by Beverly T. Lynds from

images taken during the National

Geographic Society–Palomar Observatory

Sky Survey (POSS). A few lesser-known

catalogues provide coverage of dark

targets at southerly declinations. For

example, the Sandqvist Lindroos (SL)

catalogue, compiled by Aage Sandqvist

and K. P. Lindroos (Stockholm

Observatory) as part of their study of

formaldehyde in dark dust clouds, lists

42 absorption nebulae detected in the

Whiteoak fields. (The Whiteoak fields

extended POSS southward, capturing

100 fields between declination –36°

B228

SL 11

SL 7

Be 149

SL 8

δ

ε

φ^1

φ^2

γ

η

θ

υ

ω

ξ

ψ^1

ψ^2

χ

δ

LUPUS

SL 12

15 h 40 m

–34°

15 h 40 m 16 h 00 m 15 h 50 m 15 h 30 m 15 h 20 m

–36°

–38°

–40°

–42°

–44°

SL 13

5986

Star magnitudes

5

4

3

6

7

8

j

r

LUPUS

Be 148

SL 12

s^1

s^2

–34°

–35°

–36°

–33°

16 h 00 m 15 h 55 m 15 h 50 m 15 h 45 m 15 h 40 m 15 h 35 m

B228

SL 13

Star magnitudes

7

6

5

8

9

10

DARK NEBULAE