SkyandTelescope.com September 2014 57Sue French welcomes your comments at [email protected]. Sue French
semi-detached splash of about 35 bright to faint stars as
seen through my 105-mm refractor at 28×. The group
covers about 26′× 13 ′, elongated northeast-southwest. Its
two brightest stars are magnitude 7, the northern one
shining yellow-orange. Some lovely multiple stars inhabit
the fi eld. ES 2692 is a nicely matched, east-west pair of
9.6-magnitude stars that lies off the cluster’s eastern side.
North of the cluster, ΟΣ 404 is a wide double made up of
a bright gold star with a considerably fainter companion
to its east-southeast. At low power ES 660 looks like two
unequally bright stars sitting east of and making the
pointy end of an isosceles triangle with the cluster’s two
brightest stars. However, boosting the magnifi cation
to 87× shows that the apparently brighter member of
the pair is actually two closely spaced stars, and ES 660
becomes a cute little arc of 10th-magnitude suns.
Alessi-Teutsch 11 is thought to be 1,800 light-years
distant and 140 million years old.
Sliding 1.6°° south-southeast from 23 Cygni brings
us to the open cluster NGC 6856. It looks very small
through my 130-mm refractor at 37×, revealing only two
faint stars and several very faint ones that show better
with averted vision. A golden 8th-magnitude star lies
12.5′ to its west-northwest. At 164×, I count nine stars
in a blocky, 2′× 1½′ group and one outlying star to the
east. The central knot is a tight little collection of 13 stars
through my 10-inch refl ector at 187×.
NGC 6856 is missing from many lists of deep-sky
objects because it was deemed nonexistent in the Revised
New General Catalogue of Nonstellar Astronomical Objects
(Jack W. Sulentic and William G. Tiff t, 1973). Nonethe-
less, it’s fairly obvious in backyard scopes. NGC 6856 is
now considered to be a true cluster. It is very old — 1.8
billion years — and 5,600 light-years away from us.
On the opposite side of the North America Nebula,
let’s call on the attractive double star 61 Cygni, also21 h 05 m 21 h 00 m 20 h 55 m 20 h 50 m+45°+44°+43°+42°+46°69976996Cr 428Teutsch 2255565760ξIC 5068Pelican NebulaNorth America NebulaIC 50707000Star magnitudes54106
7
8
9Stars, Clusters, and Nebulae in North Central Cygnus
Object Type Magnitude Size/Sep. RA Dec.
North America Nebula Emission nebula 3.8 2.0° × 1.7° 20 h 58.0m +44° 20 ′
NGC 6884 Planetary nebula 10.9 6.0′′ 20 h 10.4m +46° 28 ′
Alessi-Teutsch 11 Open cluster — 26 ′ 20 h 16.4m +52° 06 ′
NGC 6856 Open cluster 10.4 3.2′ 19 h 59.3m +56° 08 ′
61 Cygni Double star 5.2, 6.1 31.5′′ 21 h 06.9m +38° 45 ′
Berkeley 56 Open cluster — 4.0′ 21 h 17.6m +41° 50 ′
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.known as Piazzi’s Flying Star or Bessel’s Star. It’s one of
the closest star systems to the Sun, only 11.4 light-years
away. The pair’s motion through space and nearness to us
give it an extraordinarily rapid apparent motion across the
backdrop of distant stars. The motion is particularly easy
to detect now, because the brighter component is fl ying
past a 10.7-magnitude background star, as described on
page 50 of the August issue.DSW layout.indd 57 6/23/14 12:17 PM