About Astronomy

There is a large, confusing array of eyepieces available to the amateur astronomer, ranging from prices of $40 (Good for beginners) to $500 (The Nagler, Radians, and Panoptics).  When shopping for an eyepiece, there are several things you should consider:

• Focal length- The focal length of an eyepiece is its size, and determines the magnification power of the eyepiece.  The power of the eyepiece can be determined by a simple equation:  The telescope's focal length divided by the eyepiece's focal length.  For instance, a 1200mm focal length telescope using a 25mm eyepiece will yield a magnification of 48x.
• AFOV- The AFOV, or Apparent Field Of View, is how large the circle you're looking through is.  If you ever purchase an expensive eyepiece, you're most likely paying for two things:  Optical quality and AFOV.  While the cheaper Plossls yield an AFOV of around 50*, expensive Nagler eyepieces yield AFOVs of 82*!  That kind of AFOV will make you feel like you're there, instead of just looking a an object from far away.
• Eye Relief- The distance where the eye is positioned from the lense at which you can see the whole field of view.  As a general rule, the smaller the focal length of the eyepiece, the less eye relief.

If you keep these things in mind while shopping for an eyepiece, you'll be able to determine which eyepiece is best for your budget by yourself.

A barlow is like an eyepiece that when placed between the focuser and the eyepiece, doubles, triples, or even quadruples the power of your eyepiece.  They are very useful because in a way, they double the amount of eyepieces that you have.  Also, they allow you to use a high magnification with low power, high field of view eyepieces.  If you use a normal high power eyepiece, you'll be looking through a peephole.  Have you ever seen a really big eyepiece that says it's focal length is a lot smaller than it really is?  That's because it has a built-in barlow.  One bad thing about barlows is that since you're looking through more glass, the objects will appear dimmer.  That isn't good for Deep Space Objects.

Picture from OPTcorp.com

Although most telescopes come with two eyepieces, once you want more, get a Plossl.  They are upper-middle class eyepieces that are excellent for beginning amatures. they cost around 50-$60.

Picture from OPTcorp.com