Sky and Telescope - October 2017 - 51

-6°

Sept 1

k

Pat

ho

AQUARIUS

Mar 1

Oct 1

Feb 1
Nov 1

f Ur

anu

s

Jan 1,
2018

Dec 1

+8°

Feb 1

PISCES
+

i
1h 50m

1h 40m

A BRIGHT PLANET usually attracts
attention in the very late night long
before it comes to opposition. But you
have to be a dedicated planet chaser to
net dim Uranus and Neptune before
they become conveniently placed in the
evening sky. Which, for the next decade
or so, will continue to mean fall and
early winter.
Neptune, magnitude 7.8 in Aquarius,
is at opposition on September 5th. Uranus, in Pisces, comes to opposition on
October 19th. At magnitude 5.7, Uranus

pearance 3:31 a.m., reappearance
4:15 a.m. MDT; Chicago, d. 4:37,
r. 5:27 a.m. CDT; Austin, d. 4:18, r.
5:19 a.m. CDT; Toronto, d. 5:47, r.
6:32 a.m. EDT (early dawn); Atlanta,
d. 5:25, r. 6:33 a.m. EDT (early dawn);
Pittsburgh, d. 5:38, r. 6:35 a.m. EDT
(early dawn); Washington, DC, d.
5:37, r. 6:41 a.m. EDT (brighter dawn);
New York, d. 5:44, r. 6:43 a.m. EDT
(bright dawn); Boston, d. 5:50, r.
6:44 a.m. EDT (dawn to daybreak).
* Detailed predictions for hundreds of
locations, with the altitudes of the Sun
and Moon, are at lunar-occultations.
com/iota/bstar/bstar.htm.
(The page for each star there displays
three long tables with less-than-obvious
divides: for the disappearance, the reappearance, and the locations of cities.)

Star magnitudes

83

+6°

Star magnitudes

+10°

4

Pat

-8°

5
6
7
8
9

1h 30m

23h 10m

h
Jan 1,
2018

h o Sept 1
f N
ept Oct 1
une Nov 1

23h 00m

is detectable with the naked eye if you
have a good dark sky. Both planets are
in the "Great Water" region, which the
Great Square of Pegasus lords over from
high above.
The bottom side the Great Square just
made it into the top of our wide-ﬁeld
chart on the facing page, which shows
stars to 7th magnitude. That's more than
enough for ﬁnding brighter Uranus. Use
the blowup above of Uranus's immediate
area to pinpoint where it will be on its
path for your date.

UT

Oct.

UT

3

5:15

1

21:22

6

2:04

4

18:10

8

22:53

7

14:59

11

19:41

10

11:48

14

16:30

13

8:36

17

13:18

16

5:25

20

10:07

19

2:14

23

6:56

21

23:03

26

3:44

24

19:52

29

0:33

27

16:40

30

13:29

These geocentric predictions are from the
heliocentric elements Min. = JD 2452500.179 +
2.867335E, where E is any integer. At any random
time you glance up at Algol, you have a 1 in 30
chance of catching it at least a magnitude fainter
than normal.

Dec 1

22h 50m

Fainter Neptune will require using
the Neptune enlargement above at your
eyepiece. But Neptune this season will
be easier to locate than usual; it's just a
degree or so from Lambda (λ) Aquarii,
magnitude 3.7.
* Having trouble ﬁnding faint objects
with a telescope? Brush up on the necessary tricks at skyandtelescope.com/
charts. The key: You need to know the
scale and the orientation of your ﬁnderscope view (or main-telescope eyepiece
view) compared to your charts.

Minima of Algol
Sept.

4
5
6
7
8
9

29
30

18

PERSEUS
38

Algol

21

TRIANGULUM

34

» With autumn returning, Perseus is
rising into the northeastern evening
sky. Every 2.7 days, Algol (Beta
Persei) dips from its usual magnitude 2.1 to 3.4 and back. Use this
chart to carefully estimate its brightness with respect to the convenient
comparison stars of magnitude
2.1 (Gamma Andromedae) and 3.4
(Alpha Trianguli).

s k y a n d t e l e s c o p e . c o m * O C T O B E R 2 0 17

51
http://www.skyandtelescope.com/charts http://www.skyandtelescope.com/charts http://www.skyandtelescope.com
Sky and Telescope - October 2017

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