June 22nd, 2008 by 
Alan
Beginner astronomers need to be careful with these items as they tend to go way overboard. There are various designs and different lenses for different viewings. You need to figure out what you will be looking at and go from there. You may need two to three different eyepieces, but no more than that. Here is a simple guide to the different eyepieces and cost involved
The most popular is the Plossl. It uses four to five elements and have a wider field of view than Orthoscopic lenses. It usually ranges from 50-52 degrees. They run between $50-$150
For general use, the Orthoscopic lenses were considered the best. They use four elements and are good for planetary viewing. They have a 45 degree field of view. They run between $40-$100
The Kellner is a general purpose lens. It has a three element design and a 40-45 degree field of view. They run between $30-$50
The Ramsden and Huygenian are good solar lenses. They have two element designs. They are supplied with the least expensive telescopes and have very narrow fields of view. They cost between $25-$40
Barlow lenses are a great piece to have. They can double or triple the magnification of your eyepiece. They run between $60-$100
Erfles are not as favorable today. They use six elements and and a 60-65 degree field of view. They run between $75-$150
Televue has come out with some designs for eyepieces. The six element Panoptic has a 67 degree field of view. It runs between $200-$400. The other is a seven to eight element Naglers. This lens has an 82 degree field of view and runs between $175-$425
Pentax also makes a seven element lens, the SMC-XL, that runs around $250 each. It is thought that these exceed the what th Televues can do.
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