Sky and Telescope - November 2015 - 52

OBSERVING

Deep-Sky Wonders

NGC 7209

ANTHONY AYIOMAMITIS

SS Lac

First cataloged by William Herschel in 1788, the loose open cluster NGC 7209 is
notable for the bright blues and oranges of its member stars.

trouble spotting it, just raise the magniﬁcation a bit.
The trio's primary star is the eclipsing binary V402 Lac.
The gravitational dance of the stars has a period of 3.78
days, winking with unequal brightness dips as each star
eclipses the other. Even during the deeper minimum,
the binary dims only a few tenths of a magnitude.

8 Lacertae
Comp.

Mag(v)

5.7

6.3

10.4

9.1

7.3

11.0

14.1?

14.6

~11

13.0?

A
B
JG

I
F

MARTIN GERMANO

November 2015 sky & telescope

One night while armed with my 10-inch scope, I was
seeking galaxies with the magnitude ﬁ lter on my software atlas set fairly bright. I was surprised to see that the
galaxy UGC 11973 made the cut. At 88× this highly elongated galaxy leans northeast with a moderately faint star
near each tip. The interior is about ¾′ long and visible
with direct vision, while averted vision reveals fainter
extensions that roughly double the galaxy's length. If
you'd like to reach beyond galaxies with NGC designations, this is a good choice for a moderate-size telescope.
One of my favorite sights in the Lizard is the multiple star 8 Lacertae. It has 11 components listed in the
continually updated online Washington Double Star
Catalog (WDS) maintained by the United States Naval
Observatory (http://is.gd/usnowds). Although some of
the components aren't physically related to one another, I
had a lot of fun hunting them down.
I started with my 130-mm refractor at 23× and saw a
very cute arc of four stars spanning 1.4′. Component A
sits at the northern end of the curve, which then sweeps
southeast through B, C, and D. As you can see in the table
of magnitudes, the components aren't lettered strictly by
decreasing brightness, and star C is fainter than D. Two
distant companions are also visible. F sits a fair piece (1.6′)
south-southwest of D, and E is way oﬀ (4.9′) to the west of
F. At 117× I saw a faint star making a neat rectangle with
C, D, and F, but it's not given as part of the system. Try as
I might, I couldn't spot any more components, even when
I upped the magniﬁcation to 273×.
Undaunted, I tried my luck with my 10-inch reﬂector on the following night. At 299× I saw one star of
the close JG pair. Now and then I thought I glimpsed
component I close southwest of D, but I couldn't be sure.
Two nights later, I rolled out my 15-inch scope. At 345× I
could readily see star I, which is separated from D by 10″.
Stars J and G were obvious as well, the brighter one situated 10″ west-southwest of its neighbor. There was one
component I couldn't see, star H, which is a snug 1.4″
west-southwest of C and four magnitudes fainter.
The JG pair presents something of a puzzle. The
WDS places the brighter star east-northeast of its
neighbor, which is clearly not the case (G lines up westsouthwest of dimmer J) and indicates that the listed
magnitudes of those stars are inaccurate. Adding more
interest to the scene, star A is a tight binary indivisible through the eyepiece, but it has been detected with
speckle interferometry. In this imaging process, many
millisecond exposures are statistically analyzed and
combined by computer to overcome the blurring eﬀects
of atmospheric turbulence.
Both challenging and pretty, 8 Lacertae can give any
observer yet another reason to love the night. ✦

http://www.is.gd/usnowds

Sky and Telescope - November 2015

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