Night Sky Notes for April 2016 Geoff Mitchell
The April night sky now shows the spring constellations but with daylight saving time (BST) and the Sun moving north of the celestial equator , twilight skies mean later observing hours as we head into the summer months. The bright planet Jupiter is well placed high in the south by early evening. The spring night sky contains many fine objects to view with both binocular and small telescopes and this month has a few notable events of special interest. The constellations of Leo and Virgo contain a large cluster of Galaxies , the Virgo Super cluster , visible as faint misty patches in moderate sized telescopes – Galaxy hunting season is now `open` . Our own Milky Way galaxy stretches from the constellation of Auriga , marked by the bright star Capella overhead through the constellations of Perseus and Cassiopeia and down into the north west . This faint band of stars is best seen on clear dark moonless evenings from darker locations outside the town. Comet 252P/LINEAR moves north into UK skies as a binocular object in our dawn skies in early April and a late evening object (telescopically) later in April.
The familiar asterism of the plough in the constellation of Ursa Major, The Great Bear is seen high in the north east with its handle or tail pointing towards the horizon mid evening. Use the right hand pair of stars Dubhe and Merak (The pointers) to find the faint pole star Polaris and the position of North.
Look to the west early evening (8pm BST) to see the elusive planet Mercury low in twilight during early April. Telescopes shows a tiny disk, Mercury also has phases (like our Moon) , currently Mercury is approaching 50% phase as it reaches maximum elongation from the Sun on April 18th .
The spring constellation of Leo rises early evening, the brightest star Regulus and the `reversed question mark ` shaped star asterism of `The Sickle` makes this an easily recognisable constellation. Leo stretches eastward and is marked at the tail end by the star Denebola. Leo contains some moderately bright galaxy pairs visible in moderate sized telescopes on moonless evenings. M65/M66 and NGC 3628 form the famous galaxy triplet, all three galaxies being visible in the same telescopic field of view.
Jupiter currently in the constellation of Leo and appears to move in retrograde motion (backwards with respect to the stars of Leo as viewed from Earth during April, this is due the planet being recently at opposition Jupiter is still well placed for observing / imaging this month, small telescopes show the four bright moons discovered by Galileo in 1610 and the famous cloud belts. The Great Red Spot is currently more subtle and straw coloured and has been fading recently. Jupiter’s Galilean moons show shadow transits and go into eclipse behind the planet and with the current favourable orbital plane alignment which occurs every six years some moons can eclipse each other as seen from Earth. A 21cm aperture or larger telescope is recommended to see the tiny dark shadow disks of the Galilean moons cast onto the cloud tops of Jupiter turbulent atmosphere.
The galaxy rich constellations of Virgo and Coma Berenices can now be seen rising by mid evening. The Virgo cluster of Galaxies has many relatively bright galaxies visible in moderate sized telescopes on moonless clear evenings. Use the star Vindemiatrix as a starting point, a few of the brighter galaxies are visible as tiny `smudges`.
Mars is located in the constellation of Scorpius, rising low in the south east late evening in late April, opposition is in late May. The `red` planet is easy to spot and is placed near to the head of the Scorpius. From the UK we only get to see the top part of Scorpius, but its still an constellation worth looking at with binoculars. Antares is the brightest star, a red giant star. Just close to Antares, binoculars or telescope show the globular cluster M4.
Saturn positioned low in the constellation of Ophiuchus now rises by late evening in late April, reaching opposition in early June. It is however rather low as seen from the UK, but has its ring system wide open, a classic view of this gem of the solar system. Small telescopes will show the rings and the brightest moon Titan. Larger telescopes show up to six or so fainter moons and any white oval features on the planets disk.
Currently both Saturn and Mars in particular can be seen to show retrograde motion against the stars as opposition approaches. Below Mars is the bright red star Antares , as the star name implies Antares is `Against Mars or the rival to Mars ` it is easy to see this when Mars and Antares are close together in the April skies.
Low in the north east Lyra is the radiant for the April Lyrids meteor shower, best seen in the early hours but with a rather low zenith hourly rate (ZHR) of just 18 meteors per hour. Lyra heralds the approach of summer skies.
Planets in April
Mercury is better placed low after sunset in our evening twilight skies early in the month., with greatest elongation on April 18th (20°)
Venus is poorly placed in the dawn skies, rising just before the Sun. Super conjunction is in June.
Mars is visible low in the east late evening in April. Mars is in retrograde motion ahead of opposition in late May.
Jupiter shines brightly in the south on the Leo early evening and is at now passed opposition but offers some good views in April (Public open evening planned for April 5th – see www.lutonastrolink.org.uk for details.)
Saturn now rises by late evening during April and will be at opposition in early June in our evening skies.
Uranus is placed in our daytime skies – best views in autumn skies.
Neptune is placed in our daytime skies – best seen in autumn skies
Moons Phases in April
New Moon April 7th Moonless, best time for deep sky observing and comet observing.
First Quarter April 14th Best days to see shadow details in lunar craters (early evening)
Full Moon April 22nd Best days to see bright ray craters like Copernicus / Tycho.
Last Quarter April 30th Moon visible in daytime skies. Do not look directly at the Sun.
Meteor showers: April Lyrids, rather low rates, best in early morning April 18th to 25th.
The highlights of the month
Mercury in twilight evening skies during early April – best seeing conditions, April 5th to 18th
April skies, Milky Way visible high overhead on moonless evenings in darker skies.
Jupiter dominates our evening skies, cloud belts and four of Jupiter’s moons visible in a small telescope.
Double cluster, on the Perseus /Cassiopeia border high overhead, nice pair of star clusters.
Pleiades (Seven Sister’s) star cluster (M45) and Hyades cluster in Taurus (lunar occultation April 10th)
Beehive cluster (M44) visible to the unaided eye but best seen with binoculars.
Comet 252P/ LINEAR moves north into UK skies in April (see notes) visible in binoculars
Telescopic triplet of galaxies M65/M66/NGC3628 in the constellation of Leo
Virgo cluster of Galaxies, brighter members of the cluster can be seen with small telescopes or binoculars.
International Dark Skies Week – LAS Public Open Observatory evening April 5th see web site home page for details
ISS Visibility – Early evening / mid evening passes during the first week in April – see web site for link / details
More detailed sky notes and LAS Newsletters, Finder charts are available to LAS members via the Members` page on the LAS Website www.lutonastrolink.org.uk