Quick guide to cool astronomy pictures. SOLAR SYSTEM STAR CLUSTERS NEBULAE GALAXIES

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EYEPIECES

	Eyepieces make all of the difference in a telescope.  It is not the telescope that does the magnifying.  The telescope collects the light.  The focal length of the eyepiece is what determines the magnification.  The focal length of the telescope is a constant.  Eyepiece focal lengths generally are between 2mm and 60mm.  To determine the amount of magnification, take the focal length of the telescope and divide it by the focal length of the eyepiece.  So, if you have telescope with a 1000mm focal length and you use a 10mm eyepiece, you have achieved 100x magnification.  If you used that same eyepiece in a telescope with a 2000mm focal length, you have achieved 200x magnification. There are two main barrel sizes for eyepieces, 2" and 1.25".  The one you use depends on the size of the eyepiece holder that is attached to the telescope.  This does not affect magnification in any way whatsoever.  A barlow lens is a common addition to any eyepiece.  A barlow increases the focal length of the telescope, thereby allowing for greater magnification.  So, if your telescope has a focal length of 1000mm, a 2x barlow would make it a 2000mm focal length telescope, thereby doubling the magnification of the telescope.  Generally, the highest useful magnification of any telescope is 50 - 60 times it aperture.  Thus, if you have a 8" telescope, you are limited to about 480x magnification.  The lower the focal length of the eyepiece, the greater the magnification. So, the lowest focal length eyepiece that my telescope can handle is the best right?  Not necessarily, while magnification is important, it is only one part of the equation.  If you are viewing planets or the moon, higher magnification will make the object appear larger, revealing more detail.  However, the planets and moon are just a few of the tens of thousands of object to look at.  Generally, the shorter the focal length of the eyepiece (meaning the greater the magnification), the smaller the field of view.  This means that you will be looking through a tiny hole in most types of eyepieces when using high magnification.  When using a low power eyepiece, the field of view is significantly wider meaning you can see a bigger "slice" of the sky and it is much easier to look through.  Many objects, such a open clusters are better viewed through a low power eyepiece.  There are many types of telescope eyepieces that are used for astronomy.  There are Huygens, Plossel, Nagler, Ramsden, Erfle, Kellner, and Konig just to name some.  These eyepieces are usually named after the people that designed them.   You can have the best telescope in the world, if your eyepieces are of poor quality, the image will be of poor quality.  Good quality eyepieces are essential to quality viewing.  In this author's opinion, Televue eyepieces are the best around, but come at a hefty price.  Their Nagler line of eyepieces are truly tops, but exceed $250.00 for each eyepiece.	Televue Eyepiece Televue Barlow lens

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