Sky & Telescope - August 2024 - 49

STELLARIUM
This evocative composite image by
Miguel Claro of Lisbon, Portugal, shows
more than 100 meteors captured over four
consecutive nights during the 2023 Perseid
meteor shower. He photographed the
display from Portugal's Alqueva dark-sky
reserve, where exceptional views of the
Milky Way and the zodiacal light (also faintly
visible in this photo) are possible.
can trace a luminous streak back to
the radiant, it's a genuine Perseid.
Look about halfway up the sky and
off to either side of the radiant for the
best views. In the morning hours that
means facing approximately southwest
or northwest.
The shower is active from midJuly
to late August as Earth crosses
a broad stream of debris scattered
along the orbit of Comet 109P/SwiftTuttle,
the display's parent object.
Most particles are sand-size grains,
but occasionally peanut-size pieces
flare into spectacular fireballs when
they plummet into Earth's atmosphere
at a speed of 59 kilometers per
second (132,000 mph). According
to French astronomer and meteor
researcher Jérémie Vaubaillon, Earth
will encounter five very old meteoroid
streams within the comet's
debris cloud, primarily on August
12th from midnight to 8 a.m. EDT.
You might get to enjoy heightened
activity during those hours.
I plan to get out after nightfall on
the 11th for a quick taste, and then
wake up around 2 a.m. for the main
feast. August evenings can be chilly,
so I always bring along a wool blanket
and a folding lawn chair - being
comfortable makes the experience so
much more enjoyable.
If you decide to photograph the
display, a tripod-mounted camera
equipped with a remote shutterrelease
(the modern version of the old
cable release) or an intervalometer
will do the job. That way you can let
the camera shoot photos automatically
while you kick back and take it
easy. Use an exposure time of around
30 seconds at ISO 1600 and a wideangle
lens set to its widest aperture
(lowest f-stop). With luck, you should
net some truly impressive Perseids.
Titan Transits
Saturn
AS THE TILT OF SATURN'S ring plane
shallows in advance of next spring's
edge-on presentation, the planet's
close-orbiting moons have been
undergoing transits and occultations
for some time now. Most of these are
exceedingly difficult to observe because
the moons are faint and their shadows
are mere pinpoints at Saturn's current
distance of 1.3 billion kilometers (810
million miles).
Fortunately, Titan is an exception.
It began its transit season in May when
Saturn was still poorly placed for viewing.
Titan orbits close to the equatorial
plane, but the slight inclination of its
orbit (0.35°) means that Earth and
Saturn have to be precisely aligned for
us to see the 8.4-magnitude moon pass
in front of or behind the planet's disk.
This month there are two Titan events:
a transit across Saturn's South Polar
Region (SPR) and an occultation behind
the North Polar Region.
The transit occurs on August 1st,
when Titan passes in front of Saturn
between about 4:55 UT (12:55 a.m.
EDT) and 8:09 UT (4:09 a.m. EDT).
Fortunately, the SPR is dusky gray and
Minima of Algol
Aug.
3
6
9
11
14
17
20
23
26
29
Saturn's largest moon, Titan, transits the
planet's South Polar Region on the night of
July 31-August 1. This simulated view shows
the moon at mid-transit at around 2:30 a.m.
EDT on August 1st. The moon Tethys appears
at far left along with several additional, smaller
satellites and their shadows.
could provide a sufficiently contrasty
backdrop against which you can make
out the moon's disk. Maybe. Titan
appears only 0.8″ across - a little
smaller than Jupiter's moon Europa
when the planet is at opposition.
The Titan occultation begins at
Saturn's northwestern limb, starting
about 3:44 UT on August 9th (11:44
p.m. EDT on August 8th) and wraps up
at 6:27 UT (2:27 a.m. EDT on August
9th). Titan orbits relatively slowly,
requiring more than 50 minutes for the
planet to gobble it up.
To observe these Titan events, use the
highest magnification seeing conditions
allow. Even if its disk eludes discernment,
it's fun to watch Saturn's biggest
moon in motion each time it slips in
front of or behind the planet's globe.
UT
29
8:44
5:33
2:21
23:10
19:58
16:47
13:36
10:24
7:13
4:02
These geocentric predictions are from the recent
heliocentric elements Min. = JD 2457360.307 +
2.867351E, where E is any integer. They were
derived by Roger W. Sinnott from 15 photoelectric
series in the AAVSO database acquired during
2015-2020 by Wolfgang Vollmann, Gerard Samolyk,
and Ivan Sergey. For a comparison-star chart
and more info, see skyandtelescope.org/algol.
18
30
PERSEUS
38
Algol
21
TRIANGULUM
34
Perseus approaches the zenith during predawn
hours in August. Every 2.87 days, Algol
(Beta Persei) dips from its usual magnitude 2.1
to 3.4 and back. Use this chart to estimate its
brightness in respect to the nearby comparison
stars of magnitude 2.1 (Gamma Andromedae)
and 3.4 (Alpha Trianguli).
sk yand tele scope .o r g * AUGUST 2024 49
http://www.skyandtelescope.org/algol https://skyandtelescope.org/
Sky & Telescope - August 2024

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