Eyepieces & Barlows

What is an eyepiece: A telescope collects the light of faint and/or distant objects and forms a fixed-size image of those objects at the telescope’s prime focus. An eyepiece is simply a small microscope that enlarges a portion of that image so you can see more detail.

The importance of good eyepieces: Every photon of light collected by a telescope passes through an eyepiece before it reaches your eye. That light is therefore afflicted by every optical problem in that eyepiece – and the cheaper the eyepiece, the more problems it is likely to have. A $10 eyepiece will make a $2000 telescope perform like a $10 toy. If your telescope’s eyepieces are the simple two-element designs labeled H (Huygenian), R (Ramsden), or SR (symmetrical Ramsden), they are basically toy eyepieces and should be replaced.

Eyepieces are half of your scope’s optical system, and usually the most complex half. They should be at least the same quality as your scope (preferably better). A good telescope won’t improve a poor eyepiece – but a good eyepiece will get the most out of a so-so scope.

What eyepiece should I get first: When buying your first eyepieces, resist the urge to immediately buy the highest powers possible. Very high powers require experienced observers and excellent seeing conditions (dark, clear, steady skies) to get the most from them. Medium power eyepieces, on the other hand, give good images over a much wider range of seeing conditions.