Sky & Telescope - January 2021 - SA3
What's in the
sky tonight?
When does the Sun set, and when does
twilight end? Which planets are visible?
What time is moonrise?
Welcome to the Skygazer's Almanac
2021, a handy chart that answers these
and many other questions for every night
of the year. This version is plotted for
skywatchers near latitude 30°° south -
in Australia, southern Africa, and the
southern cone of South America.
For any date, the chart tells the times
when astronomical events occur during
the night. Dates on the chart run vertically from top to bottom. The time of
night runs horizontally, from sunset at
left to sunrise at right. Find the date you
want on the left side of the chart, and
read across toward the right to find the
times of events. Times are labeled along
the chart's top and bottom.
In exploring the chart, you'll find that
its night-to-night patterns offer many
insights into the rhythms of the heavens.
The Events of a Single Night
To learn how to use the chart, consider
some of the events of one night. We'll
pick January 10, 2021.
First find "January" and "10" at the
left edge. This is one of the dates for
which a string of fine dots crosses the
chart horizontally. Each horizontal
dotted line represents the night from a
Sunday evening to Monday morning. The
individual dots are five minutes apart.
Every half hour (six dots), there is a
vertical dotted line to aid in reading the
hours of night at the chart's top or
bottom. On the vertical lines, one dot is
equal to one day.
A sweep of the eye shows that the line
for the night of January 10-11 crosses
SGA21S
2021
FOR
L ATI TUDES
many slanting event lines. Each event line
tells when something happens.
The dotted line for January 10-11
begins at the heavy black curve at left,
which represents the time of sunset. Reading up to the top of the chart, we find that
sunset on January 10th occurs at 7:06
p.m. Local Mean Time. (All times read from
the chart are Local Mean Time, which can
differ from your civil clock time by many
minutes. More on this later.)
Note that Saturn, Mercury, and
Jupiter all set within a few minutes of 8
p.m., so they are close together in the sky,
but they'll be hard to spot so soon after
sunset. Moving to the right we see that
the Pleiades transit the meridian at 8:28
p.m., meaning the famous star cluster
is at its highest in the sky. Then twilight
ends at 8:40, marking the moment when
the Sun is 18° below the horizon and the
sky is fully dark.
At about 10:02 the Large Magellanic
Cloud culminates (another way of saying
it transits). Then the two brightest nighttime stars, Canopus and Sirius, transit
at 11:03 and 11:25, respectively. Transit
times of such celestial landmarks help us
follow the march of constellations during
the night.
Running vertically down the midnight line is a scale of hours. This shows
the sidereal time (the right ascension of
objects on the meridian) at midnight.
On January 10-11 this is 7h 21m. To find
the sidereal time at any other time and
date on the chart, locate the point for
the time and date you want, then draw a
line through it parallel to the white event
lines of stars. See where your line intersects the sidereal-time scale at midnight.
(A star's event line enters the top of the
chart at the same time of night it leaves
the bottom. Sometimes one of these segments is left out to avoid crowding.)
Near the midnight line is a white
curve labeled Equation of time weav-
NE AR
30 °
SOU TH
ing narrowly right and left down the
chart. If you regard the midnight line as
the previous noon for a moment, this
curve shows when the Sun crosses the
meridian and is due north. On January 10th the Sun runs slow, transiting
at 7 minutes past noon. This deviation, important for reading a sundial, is
caused by the tilt of the Earth's axis and
the ellipticity of its orbit.
At 12:07 a.m. the red planet Mars sets,
and we can infer that it has been visible
in the sky all evening. Dim Uranus sets
at 12:28. Then at 1:59 Antares, a star
we usually associate with later seasons,
climbs above the southeastern horizon.
At about 2:52 we notice a small Moon
symbol, and the legend tells us it is a
waning crescent, rising. The first hint of
dawn - the start of morning twilight -
comes at 3:36. Then brilliant Venus rises
at 3:50. The Sun finally peeks above the
eastern horizon at 5:10 a.m. on Monday
morning, January 11th.
Other Charted Information
Many of the year's most important
astronomical events are listed in the
chart's left-hand margin. Some are
marked on the chart itself.
Conjunctions (close pairings) of two
planets are marked by a
symbol on the
Local Mean Time Corrections
Adelaide
Brisbane
Canberra
+16
-13
+4
Melbourne
Perth
Sydney
+20
+18
-4
Cape Town
Durban
Harare
+46
-3
-4
Johannesburg +8
Port Elizabeth +18
Pretoria
+8
Asunción
-10
Buenos Aires +54
Montevideo +45
Rio de Janeiro -7
Santiago
+43
São Paulo
+6
Rising or Setting Corrections
Declination (North or South)
0°
5° 10° 15° 20° 25°
South Latitude
Skygazer's
Almanac 30°S
planets' event lines. Here, the symbol
indicates the night when the planets
appear closest in the sky (at appulse), not
just when they have the same ecliptic
longitude or right ascension.
Opposition of a planet, the date when
it is opposite the Sun in the sky and thus
visible all night, occurs roughly when its
transit line crosses the Equation-of-time
line (not the line for midnight). Opposition is marked there by a
symbol. For
instance, Saturn reaches opposition on
the night of August 2-3 this year.
Moonrise and moonset can be told
apart by whether the round limb - the
outside edge - of the Moon symbol faces
left (waxing Moon sets) or right (waning Moon rises). Or follow the nearly
horizontal row of daily Moon symbols
across the chart to find the word Rise or
Set. Quarter Moons are indicated by a
larger symbol. Full Moon is always a large
bright disk whether rising or setting; the
circle for new Moon is open. P and A
mark dates when the Moon is at perigee
and apogee (nearest and farthest from
Earth, respectively).
Mercury and Venus never stray far
from the twilight bands. Their dates of
greatest elongation from the Sun are
shown by ◗ symbols on their rising or
setting curves. Asterisks mark when their
telescopic disks have the greatest illuminated extent in square arcseconds. For
example, this occurs for Mercury on the
evening of January 20th and for Venus
on December 4th.
Meteor showers are marked by a starburst symbol on the date of peak activity
and at the time when the shower's
radiant (point of origin) is highest in
the night sky. This often occurs just as
morning twilight begins. (Note that our
predicted peak of the Southern Taurids, a
sparse and ill-defined shower, falls a few
weeks earlier than in recent years.)
Julian dates can be found from the
numbers just after the month names on
the chart's left. The Julian day, a sevendigit number, is a running count of days
beginning with January 1, 4713 BC. Its
first four digits this year are 2459, as
indicated just off the chart's upper left
margin. To find the last three digits for
days in January, add 215 to the date. For
instance, on January 10th we have 215 +
10 = 225, so the Julian day is 2,459,225.
10°
0
8
16
24
33
43
15°
0
6
12
19
26
33
20°
0
4
8
13
18
23
25°
0
2
4
7
9
12
30°
0
0
0
0
0
0
35°
0
2
5
7
10
13
40°
0
5
10
16
22
29
45°
1
8
17
26
37
49
50°
1
12
25
39
54
72
Note that the Julian day does not
change to this value until 12:00 Universal
Time (UT). In Australia, 12:00 UT falls
during the evening of the same day (at 10
p.m. Australian Eastern Standard Time,
AEST). Before that time, subtract 1 from
the Julian day number just obtained.
Time Corrections
All events on this southern version of
the Skygazer's Almanac are plotted for
an observer at longitude 135° east and
latitude 30° south. However, you need
not live near McDouall Peak, South
Australia, to use the chart. Simple corrections will allow you to get times accurate
to a couple of minutes anywhere in the
world's south temperate latitudes.
To convert the charted time of an event
into your civil (clock) time, the following
corrections must be made. They are given
in order of decreasing importance.
* DAYLIGHT-SAVING TIME ("SUMMER
TIME"). When this is in effect, add one
hour to any time read from the chart.
* YOUR LONGITUDE. The chart gives the
Local Mean Time (LMT) of events, which
differs from ordinary clock time by many
minutes at most locations. Our civil time
zones are standardized on particular longitudes. Examples in Australia are 150°°E
for the eastern states (which use Australian Eastern Standard Time, AEST), and
142.5°E for the central state and territory
(an odd value that puts the minute hands
of their clocks 30 minutes out of joint
with most of the rest of the world).
If your longitude is very close to your
standard time-zone meridian, luck is with
you and your LMT correction is zero. Oth-
erwise, to get standard time add 4 minutes
to times obtained from the chart for each
degree of longitude that you are west of
your time-zone meridian. Or subtract 4
minutes for each degree you are east of it.
For instance, Melbourne, Australia
(longitude 145°), is 5° west of its timezone meridian (150°). So at Melbourne,
add 20 minutes to any time obtained from
the chart. The result is standard time.
Find your Local Mean Time correction
and memorize it; you will use it always.
The table below at left has the corrections,
in minutes, for some major cities.
* RISING AND SETTING. Times of rising
and setting need correction if your latitude differs from 30° south. This effect
depends strongly on a star or planet's
declination. The declinations of the Sun
and planets are listed each month in Sky
& Telescope.
If your site is south of latitude 30°S,
an object with a south declination stays
above the horizon longer than the chart
shows (it rises earlier and sets later), while
one with a north declination spends less
time above the horizon. If you are north of
30°S, the effect is just the reverse. With
these rules in mind, you can gauge the
number of minutes for correcting a rise or
set time using the table above left.
Finally, the Moon's rapid orbital
motion alters lunar rising and setting
times slightly if your longitude differs
from 135°E. The Moon rises and sets
about two minutes earlier than the chart
shows for each time zone east of central
Australia, and two minutes later for
each time zone west of there. Observers
in southern Africa can simply shift the
Moon symbol a third of the way to that
for the following date. Those in South
America can shift it about halfway there.
For reprints (item SGA21S, $5.95 each) or to order
a similar chart for latitude 40° north or 50° north,
go to: shopatsky.com/resource-materials/calendarsalmanacs
Skygazer's Almanac 2021 is a
supplement to Sky & Telescope
Magazine, One Alewife Center,
Suite 300B, Cambridge, MA
02140, USA, skyandtelescope.
org. ©2020 AAS Sky Publishing, LLC. All rights reserved.
http://www.shopatsky.com/resource-materials/calendars-almanacs
http://www.shopatsky.com/resource-materials/calendars-almanacs
Sky & Telescope - January 2021
Table of Contents for the Digital Edition of Sky & Telescope - January 2021
Contents
Sky & Telescope - January 2021 - Cover1
Sky & Telescope - January 2021 - Cover2
Sky & Telescope - January 2021 - 1
Sky & Telescope - January 2021 - Contents
Sky & Telescope - January 2021 - 3
Sky & Telescope - January 2021 - 4
Sky & Telescope - January 2021 - 5
Sky & Telescope - January 2021 - 6
Sky & Telescope - January 2021 - 7
Sky & Telescope - January 2021 - 8
Sky & Telescope - January 2021 - 9
Sky & Telescope - January 2021 - 10
Sky & Telescope - January 2021 - 11
Sky & Telescope - January 2021 - 12
Sky & Telescope - January 2021 - 13
Sky & Telescope - January 2021 - 14
Sky & Telescope - January 2021 - 15
Sky & Telescope - January 2021 - 16
Sky & Telescope - January 2021 - 17
Sky & Telescope - January 2021 - 18
Sky & Telescope - January 2021 - 19
Sky & Telescope - January 2021 - 20
Sky & Telescope - January 2021 - 21
Sky & Telescope - January 2021 - 22
Sky & Telescope - January 2021 - 23
Sky & Telescope - January 2021 - 24
Sky & Telescope - January 2021 - 25
Sky & Telescope - January 2021 - 26
Sky & Telescope - January 2021 - 27
Sky & Telescope - January 2021 - 28
Sky & Telescope - January 2021 - 29
Sky & Telescope - January 2021 - 30
Sky & Telescope - January 2021 - 31
Sky & Telescope - January 2021 - 32
Sky & Telescope - January 2021 - 33
Sky & Telescope - January 2021 - 34
Sky & Telescope - January 2021 - 35
Sky & Telescope - January 2021 - 36
Sky & Telescope - January 2021 - 37
Sky & Telescope - January 2021 - 38
Sky & Telescope - January 2021 - 39
Sky & Telescope - January 2021 - 40
Sky & Telescope - January 2021 - 41
Sky & Telescope - January 2021 - 42
Sky & Telescope - January 2021 - 43
Sky & Telescope - January 2021 - 44
Sky & Telescope - January 2021 - 45
Sky & Telescope - January 2021 - 46
Sky & Telescope - January 2021 - 47
Sky & Telescope - January 2021 - 48
Sky & Telescope - January 2021 - 49
Sky & Telescope - January 2021 - 50
Sky & Telescope - January 2021 - 51
Sky & Telescope - January 2021 - 52
Sky & Telescope - January 2021 - 53
Sky & Telescope - January 2021 - 54
Sky & Telescope - January 2021 - 55
Sky & Telescope - January 2021 - 56
Sky & Telescope - January 2021 - 57
Sky & Telescope - January 2021 - 58
Sky & Telescope - January 2021 - 59
Sky & Telescope - January 2021 - 60
Sky & Telescope - January 2021 - 61
Sky & Telescope - January 2021 - 62
Sky & Telescope - January 2021 - 63
Sky & Telescope - January 2021 - 64
Sky & Telescope - January 2021 - 65
Sky & Telescope - January 2021 - 66
Sky & Telescope - January 2021 - 67
Sky & Telescope - January 2021 - 68
Sky & Telescope - January 2021 - 69
Sky & Telescope - January 2021 - 70
Sky & Telescope - January 2021 - 71
Sky & Telescope - January 2021 - 72
Sky & Telescope - January 2021 - 73
Sky & Telescope - January 2021 - 74
Sky & Telescope - January 2021 - 75
Sky & Telescope - January 2021 - 76
Sky & Telescope - January 2021 - 77
Sky & Telescope - January 2021 - 78
Sky & Telescope - January 2021 - 79
Sky & Telescope - January 2021 - 80
Sky & Telescope - January 2021 - 81
Sky & Telescope - January 2021 - 82
Sky & Telescope - January 2021 - 83
Sky & Telescope - January 2021 - 84
Sky & Telescope - January 2021 - Cover3
Sky & Telescope - January 2021 - Cover4
Sky & Telescope - January 2021 - SA1
Sky & Telescope - January 2021 - SA2
Sky & Telescope - January 2021 - SA3
Sky & Telescope - January 2021 - SA4
Sky & Telescope - January 2021 - SA5
Sky & Telescope - January 2021 - SA6
Sky & Telescope - January 2021 - SA7
Sky & Telescope - January 2021 - SA8
Sky & Telescope - January 2021 - SA9
https://www.nxtbook.com/nxtbooks/aas/st_202410
https://www.nxtbook.com/nxtbooks/aas/st_202409
https://www.nxtbook.com/nxtbooks/aas/st_202408
https://www.nxtbook.com/nxtbooks/aas/st_202407
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com