Sky Diary

On the last day of March we entered Daylight Saving Time so darkness falls an hour later than in March. At the beginning of the month sunset is at 7.51pm and by the end of April it is an hour later at 8.51pm. This gives us a shorter observing evening as true darkness does not occur until around 10pm.

The winter constellations have been banished towards the west with Orion’s belt and the bright orange star Betelgeuse setting in the west at about 10pm. Gemini and Auriga are also well towards the west, but at rather a higher elevation, and Taurus, Perseus and Andromeda decorate the north-western horizon. Leo is still prominent high towards the south and overhead is Ursa Major, marked by the seven stars of the Plough. The bright and rather isolated star towards the south-east is Arcturus of the fainter constellation Boötes, and is followed in the east by the crown shape of Corona Borealis and then Hercules. In the north-east, the bright star Vega is the first sign of the returning Summer Triangle which becomes more prominent over the next few months.

It is a pity the nights are shortening and becoming brighter as April is one of the best months to see the clusters of galaxies which exist around Leo and, slightly to its east, those in Coma Berenices and Canes Venatici. Both are faint constellations not easily seen in brightening evenings but Canes Venatici is home to a few brighter galaxies, not the least of which is the Whirlpool Galaxy or Messier 51, discovered by Charles Messier in 1773. This is a glorious spiral galaxy which is interacting with a smaller galaxy known as NGC 5195. The smaller galaxy may well have passed through the larger one 50 to 100 million years ago and is now behind Messier 51. Under ideal conditions it is possible to see Messier 51 and its companion with binoculars but it really requires a 4 to 5 inch aperture telescope to get an idea of their shape. Photographic images bring out the spiral structure clearly.

Around first quarter the Moon is still very high in the April evening sky and is well worth having a look at with binoculars or telescope of any size. The changing position of the terminator, the line demarking lunar sunrise, reveals changing shadows as craters emerge into the new lunar day. With a telescope there are endless details to examine on the Moon’s surface such as craters, flat maria areas, mountains and even winding cracks and valleys with larger telescopes.

The April Lyrid meteor shower reaches its peak on the 22nd April at noon. The best times to see any of these meteors will be on the evenings of the 21st to the 23rd although sky conditions are not particularly favourable with a Moon just beyond first quarter and high in the sky. The rate of meteors expected near to maximum is only about 15 per hour under good conditions so it is unlikely to be a spectacular meteor shower. However, good displays of the April Lyrids were recorded in 1803, 1922 and 1982, so we may be surprised this year.