Sky & Telescope - January 2024 - SA8

Almanac 2024
Skygazer's
50°N
What's in the
sky tonight?
When does the Sun set, and when does
twilight end? Which planets are visible?
What time does the Moon rise?
Welcome to the Skygazer's Almanac
2024, a handy chart that answers these
and many other questions for every night
of the year. This version is plotted for
skywatchers near latitude 50° north - in
the United Kingdom, northern Europe,
Canada, and Russia.
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 7, 2024.
First find " January " and " 7 " 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 7-8 crosses many
SGA24E
F OR LAT I T UD ES NE AR 50° NORT H
slanting event lines. Each event line tells
when something happens.
The dotted line for January 7-8 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 7th occurs at 4:15
p.m. Local Mean Time. (All times on the
chart are Local Mean Time, which can
differ from your civil clock time by many
minutes. More on this later.)
Continuing rightward on the dotted
line for the 7th, we see a line for Neptune
crossing it at 4:37, but twilight is still
much too bright to look for that faint
planet. The dashed line at 6:13 marks the
end of evening twilight, the time when
the Sun is 18° below the horizon and the
sky is fully dark.
At 6:59 p.m. the brightest nighttime
star, Sirius, rises in the southeast. Then
at 7:08 the giant planet Jupiter transits
the meridian, meaning it is then due
south and highest in the sky, the best
time to view its cloud belts and four
bright moons in a telescope.
Polaris, the North Star, reaches upper
culmination near 7:56. This is when
Polaris stands directly above the north
celestial pole (by 38′ this year), a good
opportunity to check the polar alignment
of a telescope mount.
The ringed planet Saturn sets at 8:25,
so we know it has been visible, low in the
west, up to now. The Pleiades star cluster
in Taurus transits the meridian at 8:41,
followed by the Great Nebula in Orion
(10:29) and Sirius (11:38). Transits of
celestial landmarks help remind us where
the constellations are 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 7-8 this is 7h 08m. 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 weaving
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 south. On January 7th the Sun runs
slow, transiting at 12:06 p.m. This deviation,
important for reading a sundial, is
caused by the tilt of the Earth's axis and
the ellipticity of its orbit.
Pollux in Gemini transits at 12:38
a.m., and Regulus in Leo does so at 3:01.
As the wee hours continue, note the tiny
Moon symbol centered at about 5:10. The
legend at the bottom of the chart tells us
the Moon is a waning crescent, rising.
Just 3 minutes later brilliant Venus also
rises (but they happen to be about 7°
apart on this occasion).
The first hint of dawn - the start of
Local Mean Time Corrections
Amsterdam +40
Belfast
Berlin
+24
+6
Bordeaux +62
Bremen
Brussels
+24
+44
Bucharest +16
Budapest -16
Calgary
+36
Copenhagen +10
Dublin
Geneva
Glasgow
Halifax
Kyiv
London
Lyons
+25
+35
+16
+14
Hamburg +20
Helsinki
+20
-2
+41
Manchester +8
Montreal
Moscow
Munich
Oslo
-6
Ottawa
Paris
Prague
Quebec
Regina
+26
+14
+17
+3
+51
+2
-15
+58
Reykjavík +88
St. John's
+18
-5
Vancouver +12
Vienna
Warsaw
-24
Winnipeg +29
Zurich
+24
+1
Stockholm -12
Toronto
Sky & Telescope - January 2024

Table of Contents for the Digital Edition of Sky & Telescope - January 2024
