page18

What can I expect to see?

This must be the single most important question asked by beginners. I found it immensely difficult to find a publication or Web based source that really gave sufficient examples as to what I might see using my limited equipment in my location with my limited skills as a beginner.

The fact is that the beginner's expectations are often buoyed by images in magazines and books that can only be achieved through long exposure astrophotography. The human eye does not sense much if any colour at night and so the last thing you are likely to see is a colourful image! The exception to this rule is the odd planet such as Mars, Jupiter, Uranus and Neptune (if you've got enough aperture). However, despite the fact that you're likely to see colour on these planets, you aren't likely to see very much detail (atleast not if your skies are anything like mine and assuming you aren't using a scope with big aperture). The images in publications make it appear as though you'll see great detail on Jupiter, Saturn and Mars. The fact is that you'll probably struggle to see much more than the two main, red, equatorial belts on Jupiter and the main divide in the rings of Saturn. Mars will probably expose its polar cap(s) and some dark patches will be visible. More detail can be gleaned by using high quality eyepieces with fewer lens elements but even so you will need stable skies, patience and practice to pick out more details.

This last point is key. You really can train your eyes to observe more detail. I regularly notice stars with the naked eye that my wife simply cannot see. Given time these stars will become clear to her but she is not attuned to noticing faint light in a dark sky. Equally planetary and deepsky features will become more apparent with practice. This said, it is critical that you set your expectations low when searching out your first deepsky objects.

I spent a long time trying to find a book that would give a realistic view of what I should be looking for when searching out deepsky objects, for the simple reason that I couldn't find any! This despite statements such as, 'very easy to find' and other equally positive comments from the authors. The best books I have found are Stephen James O'Meara's Deepsky Companions for The Messier and Caldwell Objects. These books are very motivational and beautifully presented. They include astrophotos and O'Meara's drawings of what he saw. Two things to point out here: (a) O'Meara is a very experienced observer with excellent skills and (b) he observes from a mountain in Hawaii! More positively, O'Meara uses a 4" Televue refractor for observations in both books which means that if he can see something then you have a sporting chance of making out somwhere between 0 and 50% of what he shows in his drawings and describes in his text. So long as you accept that this is about as good as you're likely to get then you should find his books extremely useful and certainly informative.

Deepsky objects generally are very dim and they won't show any colour. However, there are exceptions and these can throw you too. If you're looking for a faint patch of light in a bright star field you may find you never find objects such as The Cat's Eye Nebula in Draco or The Blue Snowball in Andromeda. Both of these planetary nebulas appear stellar (like a star) at low power but swell to a bright, light blue, blob under power. And unlike most deepsky objects they'll take lots of power - over 300x for each of them. In general it's best to search for deepsky objects using low power, say 25-45x, where you'll get a good field of view and you'll concentrate the few photons that reach your eye into a small area thus improving surface brightness. Once you've found your target then increase power but not too far. Most deepsky objects won't take much more than 100-150x and most are best at more like 60-80x. The exception again is those small bright planetary nebulae (they're called planetaries because they look like small planets, like Neptune or Uranus, not because they have anything to do with planets!) where it's best to search with at least 60-80x magnification and maybe even 100-130x then increase magnification pretty much as far as you can.

Key to finding your target in the first place is to learn to star-hop. Using a finder chart or planetarium software, look for bright stars that can lead you to your target in small jumps. It is easiest to star-hop if you understand the field of view of your eyepiece and can project that onto your chart. In this way you can tell whether you need to move one, two or half a field of view from one star to the next. Star-hopping gets tricky when you have to take into account that the view through your eyepiece will be upside down and, depending on your scope, possibly back to front! Trying to remember which way is which is very difficult and can only come with practice.

Star-hopping is a great way of learning the constellations and I recommend learning the technique even if you have a Goto telescope. The joy of finding your target and learning the night sky is one not to be missed.