Sky and Telescope - July 2017 - 54

JULY 2017 OBSERVING
Deep-Sky Wonders by Sue French

Summer Highlights
Warm nights and dark skies are ideal for enjoying these classic beauties.

A

top our windy hill, emerald ﬁelds
turn obsidian as night sweeps her
cloak across the world. A scope is waiting, the stars appear, and I'm where
I belong. Summer nights are an ideal
time for those of us who feel at home
among the stars to lose ourselves in
some of the most beautiful wonders of
the deep sky.
Planetary nebulae are shining baubles on the dome of the sky that come

in an amazing wealth of guises. One of
the most famous is the Ring Nebula
(M57) in Lyra, which Antoine Darquier
independently discovered with a small
refractor while observing the Comet of
1779. He claimed it resembles a planet
that's fading away. Although Darquier
may have been the ﬁrst to compare
this type of nebula to a planet, it was
William Herschel who coined the term
"planetary nebula" several years later.

q Bright nebulae and brilliant star clusters sparkle along the dark dust lanes of the Milky Way
Galaxy. Taken from Cerro Paranal, Chile, the image below, which shows the summer Milky Way between Sagittarius and Scorpius, was assembled from 52 different sky fields composed from about
1,200 individual images taken through B, V, and R filters with a 10-cm refractor. The final mosaic
represents a total of 200 hours exposure time.

My 130-mm refractor at 23× clearly
shows M57 as a very small nebula
bracketed by the stars Beta (β) and
Gamma (γ) Lyrae. Its ring-like structure
reveals itself at just 37×. At 117× the
annulus becomes distinctly oval, with
ends that are dimmer than its sides.
The ring's interior isn't as dark as the
sky, creating an overall effect that John
Herschel likened to "gauze stretched
over a hoop." M57 bears magniﬁcation well and appears quite stunning at
234×. Variations in brightness along the
rim are accented at this higher power,
and the ring's interior appears rounder
than its outer periphery, as shown in
my sketch on the next page.

Milky Way Galaxy

M21
Trifid Nebula

Lagoon Nebula
3 Sgr
Rho Ophiuichi

Butterfly
Cluster

NGC 6357

NGC 6334

54

J U L Y 2 0 1 7 * SK Y & TELESCOPE

ESO / S. GUISA RD

M7

Sky and Telescope - July 2017

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

Contents
Sky and Telescope - July 2017 - Cover1
Sky and Telescope - July 2017 - Cover2
Sky and Telescope - July 2017 - 1
Sky and Telescope - July 2017 - Contents
Sky and Telescope - July 2017 - 3
Sky and Telescope - July 2017 - 4
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Sky and Telescope - July 2017 - Cover3
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