Sky and Telescope - February 2017 - 55

SK E TCH: U WE G L A HN; SPIROG R A PH NEBUL A: N ASA / HUBBLE HERITAG E TE A M (STSCI / AUR A)

ers see in this nebula. Through my 130mm refractor at 23×, I see the bright
central star wearing a thin, pinkish-red
fringe. At 63× there is less color, but the
nebula is more obvious. My 10-inch
reflector at 70× displays a hue that I'd
call dusty rose. At 118× IC 418 is small,
oval, and annular. It's still garbed in
some indistinct shade of red, but when
I use higher powers the color starts to
look bluish grey or is lost altogether. The
oval annulus is better seen at 220× and
rakishly leans north-northwest. Averted
vision (the practice of directing your
gaze a bit to one side of a dim object so
that its light will fall on a more sensitive area of your eye's retina) makes the
nebula seem considerably brighter.
Professional astronomers dubbed IC
418 the Spirograph Nebula, because the
interwoven filaments seen on its Hubble
Space Telescope image resemble patterns
that can be drawn with a child's toy
marketed as Spirograph. You can play
with a similar pattern-generator online
at http://nathanfriend.io/inspirograph/.
Strictly speaking, the Hubble image
doesn't show true colors, but rather
maps light emitted by different elements.
Red represents singly ionized nitrogen
(N II), which dominates the relatively
cool outer region of the nebula, and blue
shows doubly ionized oxygen (O III),
which reigns in the hot interior of the
nebula. Hydrogen-alpha (Hα) emission
is mapped as green, and it modifies the
hues seen where red gives way to blue. In
reality, both the nitrogen and hydrogen
lines singled out by their filters are nearly
identical shades of red, while the chosen
oxygen line glows green.
Many galaxies inhabit Lepus, and
an interacting pair made up of NGC
1888 and NGC 1889 resides 1° northeast of Nu Leporis. I can just spot the
brighter galaxy, NGC 1888, in my 130mm scope at 48×. At 102×, the galaxy
appears slender and about 1½′ long
north-northwest to south-southeast.
It grows slightly brighter toward the
center. The 10-inch scope shows this
strip of light surrounded by a faint, thin
halo. Little NGC 1889 finally makes
its appearance through the 10-inch at
220×. Its faint roundish spot harbors a

starlike nucleus and nuzzles the larger
galaxy's east-northeastern flank near its
core. This close-knit pair lie about 110
million light-years away from us.
Sweeping southeast from Lambda,
you'll come to a 5th-magnitude star
that slightly outshines Nu, yet was
never granted a Greek-letter Bayer designation. Instead it's known as 8 Leporis, according to its Flamsteed number.
As popular as Flamsteed numbers are,

they weren't actually used in Flamsteed's catalog or atlas, which were published after his death. To see where they
came from, let's wind back the clock.
As president of the Royal Society, Isaac
Newton felt that the Astronomer Royal,
Flamsteed, was needlessly slow when it
came to the publication of his star catalog. Having a manuscript of the work,
Newton encouraged Edmond Halley
to edit it, and this unapproved edition

Rabbit Ears
Object

Type

Mag(v)

Size/Sep

RA

Dec.

Kappa (κ) Lep

Double star

4.4, 6.8

2.2″

5h 13.2m

-12°° 56′

R Lep

Variable star

5.5-11.7

-

4h 59.6m

-14°° 48′

IC 418

Planetary Nebula

9.3

14″ × 12″

5h 27.5m

-12°° 42′

NGC 1888

Interacting galaxy

11.9

3.0′ × 0.8′

5h 22.6m

-11°° 30′

NGC 1889

Interacting galaxy

13.1

0.7′ × 0.5′

5h 22.6m

-11°° 30′

NGC 1954

Galaxy

11.8

4.2′ × 2.2′

5h 32.8m

-14°° 04′

NGC 1957

Galaxy

13.9

1.2′ × 1.2′

5h 32.9m

-14°° 08′

Iota (ι) Lep

Double star

4.5, 9.9

12.0″

5h 12.3m

-11°° 52′

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.

T This Hubble Space Telescope image of IC 418,
captured with the Wide Field Planetary Camera 2,
shows emission from ionized nitrogen (mapped to
red), hydrogen (green), and ionized oxygen (blue).

S In most backyard
scopes, teasing out the
oval shape or a hint of
color can be considered
an observing victory with
IC 418. It takes aperture
and patience to reveal the
annularity: when viewed
through a 20-inch f/4.5
Newtonian reflector, the
ring of nebulosity surrounding IC 418's central
star is more apparent.

s k y a n d t e l e s c o p e .c o m

* FEBRUARY 2017

55


http://www.nathanfriend.io/inspirograph/ http://www.skyandtelescope.com

Sky and Telescope - February 2017

Table of Contents for the Digital Edition of Sky and Telescope - February 2017

Contents
Sky and Telescope - February 2017 - Cover1
Sky and Telescope - February 2017 - Cover2
Sky and Telescope - February 2017 - 1
Sky and Telescope - February 2017 - Contents
Sky and Telescope - February 2017 - 3
Sky and Telescope - February 2017 - 4
Sky and Telescope - February 2017 - 5
Sky and Telescope - February 2017 - 6
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Sky and Telescope - February 2017 - Cover3
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