Sky and Telescope - March 2016 - 31

knots were quite obvious. In addition to
the three mentioned above, NGC 5450,
NGC 5471, NGC 5458, and NGC 5447
were easily viewable. The last, NGC 5447,
has two components, detectable both
visually and through imaging. With the
16-inch, I could see that both NGC 5461
and NGC 5462 are elongated.
The ﬁ nal three knots could be
considered mere smudges, only occasionally seen: NGC 5453 and NGC 5449
both yielded at 152×, while NGC 5451
required 229×.
It amazes me that spiral arms can be
seen in galaxies that reside in the distant
Coma-Virgo Cluster, but they can!
New Mexico's Chaco Observatory has
a public observing program that I was
privileged to direct in 2002-2003. Chaco's
25-inch Dobsonian at 275× in good seeM61. A
ing gave me my ﬁnest view of M61
long north-to-south bar holds a bright
nucleus. Toward the southern end of the
bar sparks a faint, star-like H II region.
A short arm extends from the southern
end of the bar, curling around until it
fades away just inside a 14th-magnitude
star to the west. Two arms rise from the

Spring Spirals
Object

Con

Surface Brightness

Mag(v)

Size/Sep

RA

Dec.

M81

UMa

13.2

6.9

26.9′ × 14.1′

NGC 3184

UMa

13.9

9.8

7.4′ × 6.9′

10h 18.3m

+41° 25′

M66

Leo

12.7

8.9

9.1′ × 4.2′

11h 20.3m

+12° 59′

10.4

5.0′ × 3.7′

11h

21.1m

+53° 10′

14h

03.2m

+54° 21′

NGC 3631

UMa

13.4

09h

55.7m

+69°° 04′

M101

UMa

14.9

7.9

28.8′ × 26.9′

M61

Vir

13.4

9.7

6.5′ × 5.8′

12h 21.9m

+04° 28′

M99

Com

13.2

9.9

5.4′ × 4.7′

12h 18.8m

+14° 25′

9.4

7.4′ × 6.3′

12h

22.9m

+15° 49′

37.7m

+11° 49′

M100

Com

13.4

Vir

13.1

9.7

5.9′ × 4.7′

12h

NGC 4725

Com

14.0

9.4

10.7′ × 7.6′

12h 50.5m

+25° 30′

M106

CVn

13.6

8.4

18.6′ × 7.2′

12h 19.0m

+47° 18′

8.4

11.2′ × 6.9′

13h

29.9m

+47° 11′

7.5

12.9′ × 11.5′

13h

37.0m

-29° 52′

M58

M51
M83

CVn
Hya

12.9
12.8

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 magniﬁcation of the viewing instrument. Right ascension and declination
are for equinox 2000.0.

13h 00m

12h 30m

+30°

γ

β

Star magnitudes

three hours, I used a 7-mm orthoscopic
eyepiece for its superior light transmission. It yields 261× but gives only a 10′
ﬁeld of view. I recorded a small, bright
core with a nucleus surrounded by a
darker ring, then a brighter ring at the
outer edge of the halo. With great difﬁculty, I detected the southwestern arm
leading out to the brightest sector of the
ring. This may be the toughest spiral arm
that I've ever discerned.
At 93× the 8-inch on Ursa Major's
M101 showed a fairly faint nucleus in the
small core, two barely discernible spiral
arms, and several knots. A 12.5-magnitude
star lies on the face of the galaxy 1.3′ north
of the nucleus. At 116× the scope revealed
three of the cataloged H II regions: NGC
5461 and NGC 5462 are both tiny fuzzies,
but intermittently detectable NGC 5455
just looks stellar. NGC 5461 is the easiest
to spot of these three targets.
On a night of very good seeing, my
16-inch revealed two of M101's arms at
only 76×. At 152× I detected sections of
two fainter arms and saw all ten associations or H II regions described by Steve
Gottlieb (S&T: June 2004, p. 89). Seven

4725
M64

COMA BERENICES

3
4
5
6
7

+20°

M85

α

M100

M53
M91

ε

M89

M90

M60

M98

M88

M99

M86

M84
M87

M58

M59

+10°

ο

M49

M61

δ
VIRGO
γ

0°

η

bar's northern end. The ﬁrst, long and
impressive, curves along the eastern
side of the galaxy until it peters out near
the southern end of the bar. Look for a
knot due east of the nucleus. The second
arm is short but bright; it points to the
northeast. I recorded these features on
my fourth consecutive night of observing,
after which I quit early, at only 1:30 a.m.,
for fear of falling asleep and tumbling oﬀ
the very high ladder.
But I've had luck observing Coma spirals with my own scope as well. On a rare
night with excellent seeing, my 16-inch
at 261× revealed a tiny nucleus and three
M99. The longest arm, which
arms in M99
begins on the southern side of the galaxy,
wasn't too diﬃcult; it runs westward
and then northwestward. I glimpsed the
fainter northern and northeastern arms
only with the aid of Ronald Buta's sketch
made with a 30-inch reﬂector at McDonald Observatory (S&T: May 2000, p. 126).
M100 in my 16-inch at 174× looks like
a large, round glow with a light arc along
the northwestern edge (a section of a spiSk yandTelescope.com March 2016

31
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Sky and Telescope - March 2016

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