58 August 2014 sky & telescopetrue nature with a complete spectroscopic
analysis in 1940.
Swings-Struve 1 is an interesting little
gem, and my observations of it stretch
across the past 13 years. My 105-mm
refractor at 174× shows a fairly bright but
very tiny disk, and sometimes I think I
also see a stellar point inside or near it.
The planetary nebula sits just outside a
2.3′-tall V of six stars that points north-
northeast, about halfway between the two
stars at the open end of the V’s eastern
side. Adding a narrowband fi lter to the
eyepiece makes the nebula shine brighter
than the stars.
Viewing through a 10-inch refl ector at
213 ×, I see a very faint star close south-Object Type Mag(v) Size/Sep RA Dec.
Lagoon Nebula Emission nebula ~3 90 ′ × 40 ′ 18 h 03.7m –24° 23 ′
Trifi d Ne bula Emission/re fl ection nebula ~7 20 ′ 18 h 02.4m –22° 59 ′
NGC 6553 Globular cluster 8.1 7 ′ 18 h 09.3m –25° 55 ′
NGC 6544 Globular cluster 7.8 6 ′ 18 h 07.3m –25° 00 ′
Swings-Struve 1 Planetary nebula 11.4 5.6′ × 5.2′ 18 h 16.2m –30° 52 ′
IC 1284 Emission nebula — 19 ′ × 14 ′ 18 h 17.5m –19° 41 ′
NGC 6595 Refl ection nebula — 5.6′ × 3.3′ 18 h 17.1m –19° 52 ′
NGC 6589 Refl ection nebula — 4.0′ × 3.1′ 18 h 16.9m –19° 47 ′
Summer Xmas Tree Asterism 4.9 40 ′ 18 h 49.0m –18° 55 ′Type
Emission nebula
Emission/refl ection nebula
Globular cluster
Globular cluster
Planetary nebula
Emission nebula
Refl ection nebula
Refl ection nebula
AsterismSize/Sep
90 ′× 40 ′
20 ′
7 ′
6 ′- 6 ′× 5. 2 ′
19 ′× 14 ′
5.6′× 3 .3′
4. 0 ′× 3.1′
40 ′
Dec.
–24°° 23 ′- 22 °° 59 ′
–25°° 55 ′
–25°° 00 ′
–3 0 °° 52 ′
–1 9 °° 41 ′
–1 9 °° 52 ′
–19°° 47 ′
–1 8 °° 55 ′
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.
Nebulae and Globular Clusters in Western Sagittarius
OBSERVING
Deep-Sky Wonderseast of SwSt 1, perhaps the star suspected
through my little refractor. Although the
planetary’s central star is a respectable
magnitude 11.7, it remains lost in the glow
of the nebula itself. Listed magnitudes
for SwSt 1 cover a rather large range, but
I estimate a visual magnitude of 11.4 by
comparison with nearby stars. The nebula
appears blue-gray to me. Observers with
larger telescopes have reported a red-
dish hue. What color do you see? SwSt 1
responds well to an H-beta fi lter, leaving it
the brightest object in the fi eld.
A noteworthy and astrophotographi-
cally beautiful complex of nebulosity and
stars awaits us about 1½°° north-northeast
of Mu (μ) Sagittarii. With my 105-mmscope at 28×, the emission nebula IC 1284
is easily visible around the 7.6-magnitude
star HD 167815 (SAO 161273) and covers
about 11′× 7 ′ of sky. A smaller and fainter
swath of nebulosity encloses a star of simi-
lar brightness 11.4′ north-northwest. A
narrowband fi lter accentuates portions of
both nebulae. At 47× two small refl ection
nebulae southwest of IC 1284 blossom in
the fi eld of view. NGC 6595 is clearly vis-
ible around a pair of 11th-magnitude stars,
while more subtle NGC 6589 involves
a 1 0 th-magnitude star 6′ to the north-
northwest. The unimpressive star cluster
Collinder 371 runs northeast-southwest
through the nebula trio. I count 22 stars,
including fi ve pairs, most strung along
two jagged lines about 20′ long.
In my 10-inch scope at 68×, IC 1284
spans 14′× 10 ′ and nearly reaches the neb-
ulosity to its north. NGC 6595 and NGC
6589 have apparent sizes of approximately
2½′× 4 ′ and 2′× 3 ′, respectively. Collinder
371 looks more charming through this
scope, like a pair of snakes pausing for
a kiss as they wind their way northeast.
Do you see them? About 35 stars bespot
this viperous cluster. The two refl ection
nebulae are better appreciated at 115×,
especially NGC 6595, which is unevenly
illumined and considerably brighter in an
elongated, patchy area around its star pair.
Don’t be surprised if the atlas you
use has diff erent designations for these
objects. IC 1284 is sometimes called IC
1283, but the latter is part of the former.
NGC 6595 is identical with NGC 6590, and
Collinder 371 is often mistakenly labeled
as NGC 6595.
Our last stop, where glows the Milky
Way, is the Summer Christmas Tree, a
pretty asterism noted by North Carolina
amateur David Elosser. Through my
105-mm refractor at 28×, I see about 25
stars forming a fi r tree, 35′ tall with its tip
pointed north-northwest. A yellow star
tops the tree, and an orange one marks its
southwestern corner. Fittingly, the treetop
star (HD 173928 or SAO 161848) is the
brightest. This is a nice treat when winter’s
Christmas Tree (NGC 2264 in Monoceros)
isn’t available for our admiration. ✦Object TypeType MagNebulae and Globular Clusterrss in
The large emission nebula IC 1284 forms
a lovely triplet with the smaller refl ection
nebulae NGC 6589 and 6595.NGC 6589erssinnWWesstteernSSagitt
NGC 65 89NGC 6595IC 1284SERGIO EGUIVAR