Astronomy - USA (2019-10)

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To figure out what was going on, I used Photoshop

to add stars to the Stoney drawing to enhance the core’s

outer region northwest of the propeller’s radiant. Then

I darkened the core region east of the propeller’s center.

The result: The propeller’s position in Stoney’s drawing

better resembles that in the Markham drawing. Any

confusion, then, boils down to artistic impression of

starlight, not the movement or misrepresentation of the

dark propeller’s position.

How to see the propeller

The propeller is a low-contrast feature about 3' across,

whose radiant lies just southeast of the cluster’s core.

Through my 8-inch ref lector, the propeller shows up

best when using magnifications ranging from 244x to

300x. I find the two southern blades more apparent

than the northern one, owing to the increased contrast

of starlight near the core.

Look for the hook of stars to the south of the core and

work from there. I find using averted vision, then relax-

ing my gaze, works best. In other words, while using

averted vision, I set my mind at ease by thinking of

something pleasant. I do not focus on the stars, but

rather let my eyes relax while keeping my mind alert as

to where I want to look. By softening my gaze, I become

less aware of minute details and more aware of greater

shades of contrast. So give the propeller a whirl.

As always, report what you see, or don’t see, to

[email protected].

BY STEPHEN

JAMES O’MEARA

Stephen is a globe-

trotting observer who

is always looking

for the next great

celestial event.

BROWSE THE “SECRET SKY” ARCHIVE AT

http://www.Astronomy.com/OMeara

ABOVE: This image of

the Hercules Cluster

(M13) shows the dark

“propeller” feature,

to the upper left of

center in this image.

RODNEY POMMIER

LEFT: This Hubble

Space Telescope

image of M13’s core

region reveals the

position of the

propeller. NASA/ESA/

THE HUBBLE HERITAGE TEAM

(STSCI/AURA)