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skyandtelescope.com • JUNE 2019 31

Face-on spiral galaxies are

among the most graceful

objects to behold and thus are

totally worth the bit of effort

they require to observe.

Y

ou’ve probably marveled at the gr and spiral structure

in the Whirlpool Galaxy, teased out the ethereal pin-

wheel of M101, and traced the delicate branches of

Triangulum’s grandest showpiece, M33. Few deep-sky objects

elicit as much awe as these open-faced spiral galaxies with

their spectacular arching arms. The Messier list contains

several other examples, and you’ve no doubt enjoyed at least

the brightest of them.

Are there more of these majestic marvels lying just off

the well-worn track? The challenging targets on our tour of

open-faced spirals from the New General Catalogue of Nebulae

and Clusters of Stars might reward the patient and careful

observer with some delightful surprises. They are all well

placed in the June sky.

Learning to eke out faint spiral structure is a useful skill

to cultivate. First, of course, one should employ all of the

tried-and-true techniques for pushing the envelope of visual

detection. You’ll want the darkest site you can fi nd on a night

of decent sky conditions. Dark adaptation is paramount; take

the time to achieve it and take precautions to preserve it.

Large aperture will be a plus, but don’t discount your chances

just because your telescope is of modest aperture. Experiment

with magnifi cation; fi nding the optimum contrast is essen-

tial. Most important, however, is simply learning to consider

that there may be faint structure visible beyond what is

initially evident. You’re apt to miss what you don’t look for.

And, as with any faint deep-sky object, the longer you look

the more you’ll see.

Some observers like to view a photograph of an object fi rst.

It’s quite helpful to know exactly where to look for the fainter

components of a galaxy. The danger, of course, is in imagin-

ing you see something just because you know it’s there. I

prefer to check the photographs after noting these fainter

features to confi rm that what I suspected was really there.

NGC 3310 (Arp 217) lies about 4.5° southwest of the Big

Dipper’s bowl and about 10′ south-southwest of a 5.6-mag-

nitude star (HD 92095). A fi rst impression is of an abruptly

bright core within a much fainter halo. Further study reveals

a more mottled appearance, and eventually a small north-

reaching arm becomes visible. A southern arm is less contin-

uous, comprising a string of bright knots, or stellarings.

The term stellaring was probably coined by Brian Skiff

and Christian Luginbuhl in their 1990 publication, Observ-

M97

M106

M108

M109

3631 3310

3938

HD 92095

4051

β

ψ

χ

γ

67

δ

URSA MAJOR

+45°

+50°

+55°

3893

12 h 00 m 11 h 30 m 11 h 00 m

pSTELLAR NURSERY NGC 3310 in Ursa Major is an example of a

starburst galaxy, where stars are being born at a prodigious rate, espe-

cially along the spiral arms.

Prey