SKY-WATCHER AZ-Go2 - Choosing the appropriate eyepiece

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PART III: Operating Your Telescope
3.3 Choosing the appropriate eyepiece
• The magnication produced by a telescope is determined by the focal length of the eye-
piece that is used with it. To determine a magnication for your telescope, divide its focal
length by the focal length of the eyepieces you are going to use. For example, a 10mm
focal length eyepiece will give 80X magnication with an 800mm focal length telescope.
• When you are looking at astronomical objects, you are looking through a column of air
that reaches to the edge of space and that column seldom stays still. Similarly, when
viewing over land you are often looking through heat waves radiating from the ground,
house, buildings, etc. Your telescope may be able to give very high magnication but what
you end up magnifying is all the turbulence between the telescope and the subject. A
good rule of thumb is that the usable magnication of a telescope is about 2X per mm of
aperture under good conditions.
• Too much magnication and too small a eld of view can make it very hard to nd things.
It is usually best to start at a lower magnication with its wider eld of view and then
increase the magnication when you have found what you are looking for. First nd the
moon then look at the shadows in the craters!