April Night Sky

For me, April is galaxy month. The Virgo and Coma galaxy clusters offer much the best galaxy field for amateur telescopes in the entire night sky, with scores of galaxies available to observers at a reasonably dark site with an 8″ telescope; hundreds if you have a 12″. April is on balance the best month to see them because they reach their highest elevation due south before midnight.(You can still see them in later months, but then you have less night time available as the evenings stay light so late.)

The map below gives a sense of both galaxy clusters, as well as several groups of interesting galaxies in nearby Leo. But to find your way around as a star hopper like me, you need a mental image of a more detailed map. The standard guides all try to offer something here, but the most impressive I have seen is in the Interstellarum Deep Sky Atlas – large scale maps in a lay flat ring binder, that give a real sense of what you can see in an amateur telescope.( It’s not cheap; I had a weak moment at this year’s European Astrofest!) But with maps of this quality you have the incentive to browse and attempt to memorise your planned targets before you go observing, and then go back afterwards to confirm what you saw, and learn some more next time. That’s the theory, anyway!

Jupiter is at opposition this month, and therefore at its best for the year.(It is also shown on the map below, but it can hardly be mistaken as it is much the brightest object in that part of the sky). Jupiter is always the most satisfying planet to observe, as, if you can see it at all with any kind of telescope (or decent binoculars) you will see (normally) the 4 Galilean Moons, and the two main cloud belts. A good telescope on a steady night will show much more cloud belt detail; it often repays watching for some minutes, as the detail can fade in and out of view. And if you observe Jupiter more than once over an evening, you will almost always see a change in the Moons’ relative positions, or some going into, or out of, eclipse behind or in front of Jupiter.

But Jupiter’s brightness brings one disadvantage. It is so bright in a telescope that viewing it means you will lose much of the dark adaptation you need to see galaxies. I tend to get round this by observing Jupiter first and last thing in the observing session; that also allows the greatest time for the Moons to do their thing.

Jupiter and Galaxies April 2017