Sky & Telescope - August 2020 - 21

18h 30m

19h 00m
Star magnitudes

eight nights at the Oregon Star Party, for a total of about
ten hours. Most of this was done during the OSP, which had
some exceptionally clear and dark skies even by its high standards. Sometimes it pays to procrastinate.
I used my 28-inch scope for these observations. I had two
goals in mind: First, draw the Lagoon with my lowest-power
eyepiece and record the entire object without nebula ﬁlters.
Second, zoom in on the Hourglass region (again without
nebula ﬁlters) and sketch every detail visible. They were
equally challenging sketches, but oh so much fun. Based on
these rough sketches, I created ﬁnished drawings with more
accurate proportions to realistically portray how I saw the
entire object. For the low-power drawing of the Lagoon as a
whole I used magniﬁcations of 131× and 155×, and for the
close-up of the Hourglass I used 253× and 408×.

M18

M23

M25

-20°

μ
M21

M20

M22
M28

5
M8

6530

-25°

τ
M54

δ
SAGITTARIUS

The Wide View

JIMI LOWRE Y

S E R -15°

M24

3
4
5
6
7

ζ
The Lagoon Nebula (also cataloged as NGC 6523) lies in
the Sagittarius-Carina spiral arm of the Milky Way, around
4,000 light-years toward the galactic center from our vantage
point. It's an H II region also classiﬁed as an emission nebula
with an associated star cluster, NGC 6530. The Lagoon's
dimensions are roughly 54 light-years in the east-to-west
direction and 36 light-years north to south.
Although the Italian astronomer Giovanni Battista Hodierna is credited with discovering the Lagoon sometime before
1654 with a 20-power Galilean-type refractor, this misty
naked-eye patch must have been known to humans since
they ﬁrst started looking at the sky. On a dark night M8 and
M20, the Triﬁd Nebula, look like little puffs of steam just
north of the brightest part of the Milky Way as they rise out
of the Sagittarius Teapot's spout.
Because it's so bright, smaller scopes do well on the
Lagoon. My 8-inch nicely frames both M8 and M20 in a lowpower view along with an uncountable number of Milky Way
stars. Although there's a wealth of nebular detail to see in this
incredibly rich ﬁeld without a ﬁlter - even under a suburban sky - the view is instantly transformed into a "nebulapalooza" with an ultra-high contrast (UHC) or O III nebula
ﬁlter. Nebulosity becomes brighter and rich with detail, and
the outer fringes of the fainter stuff become visible.
Despite being M8's signature feature, the dark, curved
nebula cutting the Lagoon in half doesn't have a Barnard
designation. However, three much smaller and less prominent dark blotches within the Lagoon do - B88, B89, and
B296. Perhaps Barnard's photographic plate overexposed
the dark lane, but this feature doesn't have a Lynds Dark
Nebula designation, either. No matter, this highly distinctive but anonymous channel seems to ﬂow northeast before
going due north. Or maybe it's ﬂowing in the opposite
direction - how does it look to you? For now, let's refer to it
unofﬁcially as the dark channel.
The dark channel gives the Lagoon its personality. Where
else can you easily see a long, curved, dark cloud that looks
like an interstellar stream? Look closely on a good night and

18h 00m

M17

M69

-30°

SCORPIUS
M6

M70

-35°

it even seems to have small alluvial features along its length
to enhance the impression. The faint stars within the dark
channel glitter like sunlight reﬂecting off smooth, shiny river
rocks, completing the illusion. No matter how you see it, the
dark channel is a unique dark nebula and is not to be missed.
If you have access to an unspoiled sky, you may ﬁnd that
nebula ﬁlters don't improve the view as much as you might
expect. I prefer the unﬁltered view on a great night because
almost all the nebulosity remains visible and it's so much
easier to appreciate the stars within and superimposed on the
Lagoon - not to mention the surrounding richness of the
T SWIMMIN' AUTHOR SKETCHIN' The author's good friend Jimi Lowrey was on his first visit to the Oregon Star Party in 2019. Every evening,
as the author prepared to observe and sketch M8, Lowrey would saunter
by and ask "Swimmin' in the Lagoon?" in his distinctive Floridian accent.

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Sky & Telescope - August 2020

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