Page 63 - BBC Sky at Night - September 2017 UK

7+("6.<"*8,'( SEPTEMBER 63

'((3!6.< head northeast for three times the Beta- THIS DEEP-SKY TOUR
Gamma distance. A 6th-magnitude star sits
HAS BEEN AUTOMATED
just southeast of this position. Forty arcminutes
TOUR further northeast is NGC 1023, a mag. ASCOM-enabled Go-To
+10.2 barred spiral galaxy, 7.9x3.5
mounts can now take you to
arcminutes across. A 10-inch scope will
this month’s targets at the
touch of a button, with our
reveal its barred core as a thin, bright
EQTOUR app. Find it online.
while averted vision will let you see a fainter
This month we explore needle of light measuring 3x1 arcminutes, Deep-Sky Tour file for the
outer envelope. Larger apertures may
the borders of Triangulum, provide a glimpse of galaxy NGC 1023A
towards the eastern end of the faint haze,
Perseus and Andromeda a tricky 14th-magnitude target that’s the open cluster NGC 956. It can be
1.3x0.7 arcminutes across. NGC 1023 is found 2.5º northwest of M34. At mag.

Tick the box when you’ve seen each one the brightest member of the NGC 1023 +8.9 and a diameter of 7 arcminutes it is
Group, all of which are located 20.6 million completely outshone by M34 in all senses
lightyears away. SEEN IT of the word. A small telescope shows a
1 NGC 925 subtle concentration of around 10 stars,
The first stop on this month’s 3 M34 best seen with a low power. With a bit of
tour is NGC 925 in Triangulum, imagination, the brightest stars appear
which can be found by extending a line A little over 3.5º north of NGC 1023 to form an S shape. Sadly, if you do
east of mag. +4.0 Gamma (a) Trianguli is mag. +5.2 open cluster M34. manage to identify NGC 956, the bad
for 2º – the same apparent distance between With a 35-arcminute diameter, this object news is that although it is listed as an
Gamma Trianguli and nearby mag. +3.0 is well suited to small instruments using open cluster, it is now known to be
Beta (`) Trianguli. NGC 925 is an 11th- low power eyepieces. A 6-inch scope nothing more than a chance alignment
magnitude, almost face-on spiral galaxy. reveals a concentration of around 50 stars of stars! SEEN IT
Visually it appears to be 6x4 arcminutes brighter than 11th-magnitude, with the total
in size, although in reality it extends to star count believed to be approaching 5 NGC 891
11.2x6.3 arcminutes. NGC 925’s surface 400 stars. The cluster is located an estimated After the let-down of non-cluster
brightness is low and a 8-inch or larger scope 1,500 lightyears from Earth and thought to NGC 956 you’ll be pleased to know
is required to show a faint elongation in an be around 200-250 million years old. Look that our next target is more impressive.
east-southeast to west-northwest direction. out for a close pair of mag. +8.4 and +9.1 The edge-on spiral galaxy NGC 891 is
Low powers or small apertures may hint at stars, 1.4 arcseconds apart, on the southern within the borders of Andromeda, midway
a north-south elongation caused by nearby edge of the cluster. You can also navigate to between M34 and the beautiful mag.
foreground stars, the brightest of which is M34 by looking 5º west-northwest of Algol +2.2 binary star Almach (Gamma (a)
around mag. +10.0. SEEN IT (Beta (`) Persei). SEEN IT Andromedae). The galaxy has a visual
magnitude of +10.8 and is visible in a
2 NGC 1023 4 NGC 956 10-inch scope as a faint needle of light
Imagine a line from Beta to Gamma We hop across the border into that’s 10x1 arcminutes in size. A 12-inch
Trianguli. Turn 90º at Gamma and Andromeda for our next target, instrument doubles its thickness and hints
at a faint dust lane passing across the
4x2-arcminute core. This galaxy is
27.3 million lightyears away and is often
< NGC 925 is an almost face-on described in terms of how similar it looks
spiral galaxy; with a large to our own galaxy, having a similar
scope, you may be luminosity and size. SEEN IT
able to see a hint
of elongation 6 NGC 752
Mag. +5.7 open cluster NGC 752
is 3.5º northwest of Beta Trianguli.
A 6-inch scope using a low power will
reveal around 75 stars within its 45-arcminute
diameter; 60 of these cluster stars are
brighter than 9th-magnitude. A bright,
yellow-red pair of mag. +5.9 and +5.7
stars are prominent on the south-southwest
edge. Many ‘star-strings’ are visible,
including a pretty 10th-magnitude quartet
aligned southwest of the core. Another fainter
line pours south out of the core towards the
southeast. Brighter stars to the west of
NGC 752 form a hockey stick shape, with the
yellow-red pair mentioned earlier marking
the bottom. In this context, NGC 752 would CHART: PETE LAWRENCE, PHOTO: GÜNTER KERSCHHUBER/CCDGUIDE.COM
be the ball about to be hit. SEEN IT

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