Sky & Telescope - April 2021 - 49
M35 PLUS 1 Mars was a
glowing coal alongside the
bright open cluster M35 in
Gemini during the conjunction of April 19, 2006.
S SOLAR TRIPTYCH Martin Wise used an 80-mm refractor on Dec. 1, 2020 to make this set
of images of sunspot region 2786 at three different wavelengths. From left: Hydrogen alpha
(656.3 nm), which reveals the Sun's upper chromosphere; calcium K (393.4 nm), the lower
chromosphere; and visible light (540 nm), the photosphere that underlies the chromosphere.
through eclipse glasses. Solar observers
were elated, but only time will tell if
we're off to a strong start.
While it's difficult to predict how
speckled the Sun will be this spring,
now is a good time to think about
investing in safe solar filters for both
naked-eye and telescopic observations. I regularly view the Sun with an
80-mm refractor fitted with a fullaperture filter. Even at 26×, I readily
see filamentary details in sunspot
penumbrae; faculae (magnetic regions
similar to sunspots but concentrated
in small patches that appear bright
against the solar limb); and the sandgrain texture of convective cells called
granulation carpeting the solar photosphere. To view the largest sunspots,
a pair of solar eclipse glasses or #14
welder's glass does the trick.
Sunspots are key to solar activity
since the magnetic energy concentrated within them can spawn flares
that provoke spectacular aurorae.
As Cycle 25 ramps up to maximum,
it'll be interesting to see which path
the Sun takes: ho-hum, spectacular,
or something else altogether. In the
meantime, enjoy the show.
M A RS A ND M35: A L A N DY ER
Jupiter Occults 44 Cap
As noted on page 46, Jupiter has become a prominent dawn sight this
month - and just in time. On April 2nd the planet occults 5.9-magnitude
star 44 Capricorni. While the disappearance will only be visible from
western and central South America, observers in eastern North America
can witness the star's reappearance on Jupiter's western limb in twilight,
at around 6 a.m. EDT. With the planet quite low at that time, you'll need
to find a spot with an unobstructed view of the southeastern horizon.
Observers farther west will miss the occultation but instead get a nice
consolation prize: They can watch as Io passes just 0.5″ south of the star,
which will look like an extra Jovian moon (depicted in the illustration on
page 50 of the January issue). At moderate magnifications, the two objects
will appear to briefly merge then separate over the span of 10 minutes or
so. Io is nearest the star around 5:21 a.m. CDT, which favors those in the
middle of North America. Luckiest of all will be observers in some locations in Central America and northwestern South America who get to see
Io occult 44 Cap. From San José, Costa Rica, Io covers the star from 4:18
a.m. to just before 4:20 a.m. CST. The moon and star have an altitude of
22° at this time.
Mars Marches
Past M35
NOW SIX MONTHS PAST opposition,
Mars still has drawing power. From
April 25th to 27th, the Red Planet slides
by the bright (magnitude 5.1) open
cluster M35 in Gemini. On these dates,
Mars is just 4.7″ across and shines
at magnitude 1.5. On the evening of
the 26th, it will be roughly ½° northnorthwest of the cluster's center. The
planet's rusty hue will contrast nicely
with M35's diamond glitters, whether
you're using a low-power telescope or
binoculars. Viewed from mid-northern
latitudes, Mars and the cluster stand
30° above the western horizon at the
end of astronomical twilight.
Minima of Algol
Mar.
2
5
7
10
13
16
19
22
25
27
30
UT
4:21
1:10
21:59
18:49
15:38
12:27
9:16
6:06
2:55
23:44
Apr.
2
5
8
11
14
17
19
22
25
28
UT
17:23
14:12
11:01
7:50
4:39
1:29
22:18
19:07
15:56
12:45
20:33
These geocentric predictions are from the
recent heliocentric elements Min. = JD
2445641.5540 + 2.86732400E, where E
is any integer. For a comparison-star chart
and more info, see skyandtelescope.org/algol.
sk yandtelescope.org * APRIL 2 021
49
http://www.skyandtelescope.org/algol
http://www.skyandtelescope.org
Sky & Telescope - April 2021
Table of Contents for the Digital Edition of Sky & Telescope - April 2021
Contents
Sky & Telescope - April 2021 - Cover1
Sky & Telescope - April 2021 - Cover2
Sky & Telescope - April 2021 - 1
Sky & Telescope - April 2021 - Contents
Sky & Telescope - April 2021 - 3
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