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More Information  · Recommended Accessories Price $29.95 List Price $39.95 Field of view 65° Eye Relief 13mm Focal Length 17mm Number of optical elements 4 Barrel Size 1.25" Weight 3 oz. Warranty 2 years Telescope Eyepiece Formula To calculate the magnification and approximate actual field of view of this eyepiece on your telescope, enter the focal length of your telescope below and press the "Calculate" button. mm

An f/4.5 Dobsonian will yield a 3.8mm exit pupil with this eyepiece, getting into the rich field observing range. With short focal length refractors, it’s a low power, very wide field eyepiece. With the 400mm focal length Astro-Tech AT-66, for example, it provides 23.5x, a 2.83mm exit pupil, and a huge 2.77° field of view that’s more than five times as wide as the Moon.

Its 13mm eye relief is quite reasonable for this focal length, although it can somewhat limit the field for eyeglass wearers. Since the Astro-Tech field is wider to begin with than most other eyepieces in this range, most eyeglass wearers won’t find the minor vignetting to be a drawback. Those who don’t wear glasses will see a huge field at only a fraction the cost of a more exotic wide field eyepiece.

The low price of this Astro-Tech eyepiece makes it a very affordable choice to buy in pairs for use with binoviewers.