Finding your way around the sky when you are looking through binoculars or a telescope can be a nightmare, as you are looking at a very small part of the sky. If you’re searching for a particular object, a star cluster for example, it can seem nigh on impossible. But if you use a traditional method and are systematic in your approach, you’ll soon discover you can find your targets easily and have fun on the way.
Before the advent of computerized ‘goto’ systems on telescopes, astronomers had to find interesting objects to look at the hard way. It didn’t take them long to work out that by using a simple system it was possible to do this reliably every time. It’s known as star hopping, literally hopping from one view to an adjacent view to track down a desired object. In order to use it, you’ll need to get to grips with a couple of things and have some equipment to hand.
First of all you’ll need a star chart, preferably one which shows stars and objects clearly and accurately. There are several of these available which should fit the bill, or alternatively you may have some software from which you can print star charts. You’ll also need a red light torch so you can read the chart in the dark.
You’ll then need to know the field of view of your binoculars or the finder scope of your telescope. Some binoculars will have this written on them, for example ‘7″ field’ or something similar. A telescope is unlikely to tell you this. To work out the field of view of your scope or binoculars, you can divide the magnification into the aperture. Equipment with a 10×50 scope will give a field of view of 5″. The finder scope has a much larger field of view than your main telescope, so to give yourself a helping hand still further, always start with the lowest magnification eyepiece you have. This will give you the largest field of view once you have acquired your target in the finder scope.
It can be helpful to create a field of view template to use with your star chart. You can do this with just a few square centimeters of clear plastic and by using a drawing compass and felt tip pen.
The quick method here is to find a star on your chart and centre it as carefully as you can in the field of view of your binoculars or finder scope. Next check the stars at the edge of the field of view and relate them to the stars on your chart. Draw a circle on the clear plastic with the compass point on the star in the middle of the field of view. Make this wide enough to just encircle the stars which you can see at the edge of the field. Don’t forget that most finder scopes invert the image.
To find a target, start with a bright or easily recognizable star in the middle of the field of view. Note the stars at the edge of the field heading towards your quarry. Move the scope so that the stars at that edge of the field are now seen near the other. Keep heading towards your target by doing this until you find it. You’re likely to find lots of other interesting things on your journey.