Sky & Telescope - USA (2019-11)

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OPEN CLUSTERS by Al Lamperti, images by Frank Colosimo

60 NOVEMBER 2019 • SKY & TELESCOPE

B

right open clusters are quite dazzling to behold: Wit-

ness the Perseus Double Cluster. Part of their aesthetic

beauty results from the high contrast between the

brilliance of the stars and the inky-black background. Many

open clusters are bright Messier or NGC objects. A wonderful

introduction to the wide variety of open cluster designations,

some off the beaten path, can be obtained by participat-

ing in the Astronomical League’s Open Cluster Observ-

ing Program, complete with a downloadable manual (see

https://is.gd/ALopencluster).

However, as with technology, the aperture of telescopes

and persistence of observers have increased over the years,

and thus the discoveries of more challenging and perhaps

lesser-known (and observed) open clusters have increased.

Among the plethora of open cluster designations are those

described by American astronomer Ivan King in two papers

published in 1949 and 1965. There are 27 King open clus-

ters that range from the obvious to perhaps a couple of

bright stars with background haziness perceptible to the eye.

Fourteen of the 27 King open clusters whimsically reside in

“royal” constellations: Queen Cassiopeia and King Cepheus.

M52

King 20

King 9

7245

King 10

King 11

King 18

King 19

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CEPHEUS

LACERTA

CAS

23 h 30 m 22 h 30 m 22 h 00 m

+70°

23 h 00 m

+65°

+60°

+55°

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s 3

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Open clusters can be pleasing to behold but tend to be elusive.

Join the authors on their foray into the world of King open clusters.

Cepheus and Lacerta

A Full Deck of Kings

qKING 9 Let’s begin our foray

into King open clusters by going

to King 9 in Lacerta. Look for this

cluster around 5′ northeast of

NGC 7245. It’s a small, nebulous

object with only a handful of stars

resolved.

Mv* = 18 | S = 3′ | No. = 40 |

Tr = I1m | Mag. = 272×

pKING 10 Some stars

seem to be resolved in this

fi rst cluster that we’ll visit in

Cepheus, but many are faint-

er and in the background.

There’s some milkiness to

the cluster.

Mv* = 11 | S = 4′ | No. = 40 |

Tr = I1m | Mag. = 256×

(continued on page 64)

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