APRIL fromHermanus 2022 - SKY CHARTS - The Hermanus Astronomy Centre
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APRIL
from Hermanus 2022
SKY CHARTS
E V E N I N G S K Y 2 8 t h AP R I L a t 2 1 h 3 0 ( N O R T H D O W N )
E V E N I N G S K Y 2 8 t h AP R I L a t 2 1 h 3 0 ( S O U T H D O W N )
1
THE SOLAR SYSTEM
PLEASE NOTE: All events predicted are as observed from Hermanus, Western Cape, South
Africa. Times are South African Standard Time (UTC +2).
HIGHLIGHTS FROM THE SKY GUIDE
April 2022
Date Time Item
1 08h24 New Moon
02h44 Moon crosses equator
01h11 Mercury at superior conjunction
7 21h12 Moon at apogee (404 437 km)
8 21h12 Moon northernmost (+26.9º)
9 08h47 First quarter Moon
19h51 Moon less than 2º from Pollux at dusk end
Mercury crosses the ecliptic
10 Venus crosses the ecliptic
13 00h27 Mercury at perihelion (0.308 AU)
15 13h34 Moon crosses the equator
16 20h54 Full Moon (367 076 km, diameter 32.6’)
18 05h30 Moon (98%) passes 27’ north of Zubenelgenubi (α Librae)
19 20h19 Moon (88%) rises 16 minutes after Antares (α Sco) (3.8º)
17h17 Moon at perigee (365 142 km)
21 19h38 Moon southernmost (-26.9º)
22 22h21 Moon (68%) rises 9 minutes (1.9º) before Nunki (σ Sgr)
23 13h56 Moon last quarter
24 Mercury northernmost
Moon (22%) grouped within 33º of Mars, Venus, Saturn and Jupiter
27
before sunrise
28 09h50 Moon crosses equator
29 Mercury at eastern elongation (20º 36’)
30 22h28 New Moon
Venus near Jupiter
SUGGESTED EVENING OBSERVATION WINDOWS
(Lunar observations notwithstanding)
Date Moon Dusk end
24rd March Rises 23h13 (61%) 20h13
4th April Sets 20h27 (9%) 19h57
22nd April Rises 23h12 (61%) 19h35
4th May Sets 20H22 (14%) 19h24
2
SOLAR SYSTEM VISIBILITY
1st 1st
APRIL 2022 Visibility
April May
Rises: 06h55 0718 Never look at the
Sun Pisces - Taurus sun without
Length of Transit: 12h47 12h40
11.43 to 10.00 SUITABLE EYE
day Sets: 18h38 18h02 PROTECTION!
Mercury Pisces to Taurus Rises: 06h47 09h05
Magnitude +1.9 to +2.6 Behind the Sun
Transit: 12h43 14h00
Phase 100% to 10% then after sunset
Diameter 5” to 11” Sets: 18h38 18h55
Venus Capricornus to Aries Rises: 03h17 03h55
Magnitude -4.3 to -4.0 Transit: 09h54 10h03 Morning
Phase 56% to 78%
Diameter 22” to 14” Sets: 16h31 16h10
Mars Capricornus to Pisces Rises: 02h46 02h37
Magnitude +1.1 to +0.7
Transit: 09h34 09h03 Morning
Phase 92% to 87%
Diameter 5” to 6” Sets: 16h22 15h29
Jupiter Aquarius to Pisces Rises: 05h20 02h19
Magnitude -2.0 to -2.3 Transit: 11h34 08h20 Morning
Diameter 33” to 37”
Sets: 17h48 14h21
Saturn Capricornus Rises: 02h59 23h11
Magnitude +0.8 to +0.7 Transit: 09h43 05h56 Morning
Diameter 16” to 17”
Sets: 16h28 12h38
Uranus Aries Rises: 09h27 05h44 Evening then
Magnitude +5.8 Transit: 14h46 11h00 moving behind
Diameter 3”
Sets: 20h05 16h15 the Sun
Neptune Aquarius to Pisces Rises: 05h31 01h39
Magnitude +8.0 to +7.9
Transit: 11h42 07h49 Morning
Diameter 2”
Sets: 17h54 13h59
Pluto Sagittarius Rises: 01h01 20h57
Magnitude +14.4 to +14.3
Transit: 08h08 14h09 Morning
Sets: 15h16 11h16
Phase: In a telescope, the inner planets (Mercury, Venus and Mars) appear to us in phases, depending on
the angle of the Sun’s illumination, as does the Moon. The angular diameter is given in arc seconds (“). This
is the apparent size of the object as we see it from Earth.
Magnitude: we are accustomed to hearing stars described in terms of ‘magnitude’. For example the planet
Jupiter at magnitude -1.8 is considerably brighter than the star Antares (in Scorpius) at +1.05. The scale is
‘inverse’; the brighter the object, the lower the number. A ‘good’ human eye on a clear night can see down to
a magnitude of about +6.
Transit: When an object crosses the local meridian it is said to ‘transit’. The local meridian is an imaginary
line from the horizon directly north passing overhead (through zenith, see charts on page 1) to the horizon
directly south.
3
THE MOON
CRATER ARZACHEL (the Sky Guide lunar highlight)
Arzachel is remarkably clear in its structure and a favourite telescope viewing subject for amateur
and advanced astronomers.
Coordinates: 18.2ºS 1.9ºW, located in the highlands of the south-central part of the visible Moon,
close to the zero meridian (the visible centre of the Moon). It lies to the south of the crater Alphonsus
and, together with Ptolemaeus further north, the three form a prominent line of craters to the east of
Mare Nubium.
Below: Oblique view from Apollo 16, facing south above
Best seen: first quarter (9th April) and 6 days
after Full Moon (22nd April).
Type: ancient crater with high terraced walls.
Central mountain with a craterlet on its southern
slope.
Size: 98 km.
Naming: named for Abū Ishāq Ibrāhīm al-
Zarqālī, an 11th century Arab Muslim instrument
maker and astronomer. Like many of the craters
on the Moon's near side, Arzachel was named by Giovanni Riccioli. His 1651 nomenclature system
has become standardized.
Description: a relatively young lunar impact crater. The smaller Alpetragius lies to the north-west
with Thebit to the south-west along the edge of the mare. The rim of Arzachel shows little sign of wear
and has a detailed terrace structure on the interior, especially on the slightly higher eastern rim. There
is a rough outer rampart that joins a ridge running from the north rim to southern rim of Alphonsus.
The rugged central peak of Arzachel is prominent, rising 1.5 km above the floor, and is somewhat
offset to the west with a bowed curve from south- to north-northeast. The floor is relatively flat except
for some irregularities in the south-western quadrant of the crater. There is a rille system, named the
Rimae Arzachel, that runs from the northern wall to the southeast rim. A small crater lies prominently in
the floor to the east of the central peak, with a pair of smaller craterlets located nearby.
No lunar or solar eclipses will be visible from southern Africa this month.
HERMANUS MOON RISE AND SET TIMES FOR APRIL 2022
date day rise set date day rise set date day rise set
01-Apr Fri 06h53 08h59 12-Apr Tue 16h22 02h14 23-Apr Sat no rise 14h15
02-Apr Sat 07h54 19h27 13-Apr Wed 16h53 03h17 24-Apr Sun 00h21 14h58
03-Apr Sun 08h55 19h56 14-Apr Thu 17h22 04h20 25-Apr Mon 01h30 15h35
04-Apr Mon 09h55 20h27 15-Apr Fri 17h51 05h24 26-Apr Tue 02h36 16h06
05-Apr Tue 10h55 21h02 16-Apr Sat 18h21 06h30 27-Apr Wed 03h40 16h35
06-Apr Wed 11h53 21h42 17-Apr Sun 18h53 07h38 28-Apr Thu 04h42 17h02
07-Apr Thu 12h49 22h28 18-Apr Mon 19h31 08h49 29-Apr Fri 05h43 17h28
08-Apr Fri 13h42 23h19 19-Apr Tue 20h14 10h01 30-Apr Sat 06h43 17h56
09-Apr Sat 14h29 no set 20-Apr Wed 21h06 11h14 01-May Sun 07h44 18h26
10-Apr Sun 15h11 00h14 21-Apr Thu 22h06 12h22 02-May Mon 08h44 19h00
11-Apr Mon 15h49 01h13 22-Apr Fri 23h12 13h23 03-May Tue 09h43 19h38
4
METEOR SHOWERS
Observing
From SGAS Maximum 1 Velocity
Duration Prospects at Radiant ZHR
Km/sec
2022 Date/Time
max
10º south-west
poor, 61%
22nd April 16th to 25th of Vega (α Lyr)
April Lyrids moon is up for 15 49
02h00 – 05h00 April close to n.
the duration
horizon
fair, 50% moon
23rd April 15th to 28th 2.5º south of
π Puppids is up for the
LOOKING UP
CLUB STARGAZING – the possibility of club Stargazing is now back thanks to
the relaxation of the COVID restrictions. The calendar on the front page of our
website indicates our planned events.
Please consult our website for updates: http://www.hermanusastronomy.co.za
THE JEWEL BOX
NGC 4755, Kappa Crucis cluster, Caldwell 94
The following details are applicable to 28th April 2022 at 21H30
Description Open cluster Visibility on 28th April 2022
Constellation Crux
Distance 6.4 kly, 1.95 kpc Rises Transits Sets
Magnitude +4.19 (integrated) Does not rise 23h11 Does not set
Absolute mag. -7.29 visual
Apparent size 10 arcmin
Alt/Az +59º 23’ 15” / 155º 40’ 16” Naked Eye Yes, resembling a fuzzy star
J2000 lat/long -60º 20’ 00” / 12h 53m 36s Binoculars Yes, some detail
Diameter 18.7 ly, 5.7 pc Telescopes Yes, more detail
NGC 4755 - Jewel Box Cluster
NGC 4755 is a stunning open cluster in the constellation Crux, the Southern Cross. It is known as
both the Jewel Box and the Kappa Crucis cluster (after its most prominent member).
Discovery : The cluster is one of the finest objects discovered by
Nicolas Louis de Lacaille during his visit to South Africa in 1751-
1752. John Herschel described this famous group of bright
young stars as "a casket of variously coloured precious stones"
and "...a superb piece of fancy jewellery", hence the name "the
Jewel Box" cluster.
Location: The Jewel Box is only visible from southern latitudes
and appears close to Mimosa (Beta Crucis), the easternmost star
of the Southern Cross.
Properties: an A-shaped asterism with an apparent magnitude of
4.2. It looks like a single fuzzy star to the unaided eye. The cluster
contains around 100 stars within a 10' diameter area. Most are
blue giants, the brightest of which is Kappa Crucis (Bayer star
designation), a blue supergiant of visual magnitude +5.9 and spectral type B5 1a, surface
temperature 13 600 Kelvin. The fourth-brightest is a magnitude +7.6 red supergiant of class M2
that contrasts strongly against its hot, blue companions. Distance estimates for the Jewel Box
range from 6,400 to 8,150 light years. This cluster is one of the youngest known with an estimated
age of only 7.1 million years.
The Coal Sack, a huge dark area within the band of the Milky Way, appears close to NGC 4755 to
its south-west. This dark nebula is probably much closer than the cluster at only 500 to 600 light
years distance.
6Observation
the Jewel Box Cluster - Steve Crouch base
Prominent members
The central part of the cluster is framed by bright stars
making up an "A"-shaped asterism. The bar of the "A"
consists of a line of four stars. On the right (south) is BU
Cru, a magnitude +6.92 B2 supergiant and eclipsing
binary. Next to it is BV Cru, a magnitude +8.7 B0.5 giant
and Beta Cepheid variable. Next in line is DU Cru, an M2
red supergiant that varies irregularly between magnitude
7.1 and 7.6. The last of the four is CC Cru, a magnitude
7.83 B2 giant and ellipsoidal variable.
Each leg of the base of the asterism's outline is marked
by a blue supergiant star. HD 111990 (HIP 62953) is
magnitude 6.77 and B1/2. The star κ Cru itself is
magnitude 5.98 and B3.
Physical characteristics
The Jewel Box cluster is one of the youngest known open clusters. The mean radial velocity of the
Jewel Box cluster is 21 kilometres per second (13 mi/s). The brightest stars in the Jewel Box
include some of the brightest stars in the Milky Way galaxy.
Calculating its distance is difficult due to the proximity of the Coalsack Nebula, which obscures
some of its light.
Please keep in touch...
Have a look at our excellent website, edited by Derek Duckitt.
http://www.hermanusastronomy.co.za/
Contact ASSA - Get in touch with officers of the Society - we're real people with a passion for astronomy,
so contact us and let's talk!
You can find us on Facebook, Twitter, the
ASSAInfo mailing list and the ASSADiscussion Grateful thanks to the following:
mailing list.
ASSA
ASSA website http://assa.saao.ac.za
Sky Guide Africa South 2022
ASSA Deep-Sky Section
Sky Safari
Whatsappchat group: [ 074 100 7237 ] Skywatchers’ Handbook
MNASSAhttp://assa.saao.ac.za/about/publications/ Stellarium
mnassa/ Wikipedia
Nightfall https://assa.saao.ac.za/?s=Nightfall
Official Big 5 of the African Sky web page Edited by Peter Harvey -
Official Big 5 Facebook group petermh@hermanus.co.za –
ASSA Deep-Sky Section mailing list Tel: +27 (0) 81 212 9481
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