Sky and Telescope - November 2015 - 51

Sue French

Sue French welcomes your comments at scfrench@nycap.rr.com.

POSS-II / STSCI / CALTECH / PALOMAR OBSERVATORY

Merrill 2-2

NGC 7243

Σ2890

MARK PHILLIPS

us. That would place it beyond the outer reaches of our
galaxy's disk.
Another open cluster, much diﬀerent than our ﬁrst,
sits 2.7°° west of 2 Lacertae. Through my 18×50 binoculars, NGC 7209 is an obvious hazy patch generously
ﬂecked with pinpoint stars. The cluster sits within an
irregular pentagon of brighter stars. The brightest one,
north of the cluster, is an ember of smoldering orange.
My 130-mm refractor at 23× draws out 30 stars, 9th
magnitude and fainter, spanning about ¼°. Two reddishorange, 9th-magnitude stars play sentinel to the group,
one just beyond the cluster's eastern border and a more
distant one oﬀ its south-southeastern side. Increasing
the power to 37× sharpens the stars and doubles their
number. Two of the brightest, north and east of center,
have a golden sheen.
A physical member of NGC 7209 and the brightest
star in its southwestern quadrant, SS Lac is a binary
whose mutual eclipses ceased shortly before the middle
of the 20th century. The solution to this enigmatic
behavior was found in the tug of a third system member,
which shifts the plane of the inner binary's orbit relative
to our line of sight. According to a study by Guillermo
Torres, published in the Astronomical Journal in 2001,
the system undergoes a roughly 600-year cycle with two
eclipse seasons lasting 100 years each. Eclipses aren't
expected to start anew until early in the 23rd century.
Perched 1.8° south-southeast of NGC 7209, John
Herschel's multiple star h1735 (HJ 1735) is an interesting low-power triple. Observed through my 105-mm
refractor at 17×, the trio forms a straight line. Its nicely
matched bright components (magnitudes 6.7 and 6.8)
are white with a hint of blue and very widely spaced. The
third member (magnitude 9.7) is at the east-southeastern
end of the line, very close to the primary star. If you have

The relatively young open cluster NGC 7243 shines bright with blue and white
stars; at its center rests Struve 2890, a double consisting of a 9.4-magnitude
primary and 9.7-magnitude companion.

Looking into Lacerta
TYC 3624 - 2379 - 1

Merrill 2-2

Object

Mag(v)

Size/Sep

RA
22h

Dec.

15.2m

+49°° 54′

NGC 7243

Open cluster

6.4

30′

Σ2886

Double star

7.6, 10.1

20.6″″

22h 14.7m

+49°° 21′

Merrill 2-2

Planetary nebula

11.9

3.0″ × 1.4″″

22h 31.7m

+47°° 48′

05.1m

+46°° 29′

09.3m

+44°° 51′
+41°° 30′

NGC 7209

Planetary nebula Merrill 2-2 appears
almost stellar through the eyepiece;
blinking an O III ﬁlter will help you
distinguish it from its neighbors.

Type

Open cluster

h1735

Triple Star

UGC 11973

Spiral galaxy

7.7

15′

22h

6.7, 6.8, 9.7

1.8′ × 27.3′

22h

12.7

3.2′ × 0.9′

22h 16.8m

Angular sizes and separations are from recent catalogs. Visually, an object's size is often smaller than the cataloged value
and varies according to the aperture and magniﬁ cation of the viewing instrument. Right ascension and declination are for
equinox 2000.0.

Sk yandTelescope.com November 2015

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Sky and Telescope - November 2015

Table of Contents for the Digital Edition of Sky and Telescope - November 2015