|
|
 | |
 |
| This very short focal length Pentax eyepiece is designed primarily for high resolution/high contrast planetary observing with premium quality refractors. Its low level of internally scattered light will also reveal subtle lunar rilles and low contrast lunar domes that are often masked by the internal glare in lesser eyepieces. Splitting tightly spaced binary star components is also easier, due to the tighter stellar discs and cleaner diffraction rings provided by its high resolution and contrast. The eyepiece uses six lenses in three groups to provide outstanding high magnification, particularly with the unobstructed light paths of short focal length refractors. One of the elements is an ED (Extra-low Dispersion) lens made with rare earth lanthanum glass for excellent color accuracy and contrast. Using it with a 540mm 4" f/5.4 TeleVue NP-101, for example, will result in 209x (52x per inch of aperture) and a 0.47mm exit pupil (about 1/50th of an inch across). Both of these figures are very close to the generally-accepted maximum values of magnification per inch of aperture and exit pupil size for usable observing under good to very good seeing conditions for a reasonably experienced observer. Using it with the longer focal length of an 820mm 4" f/8 Takahashi FS-102 fluorite refractor will result in 318x (79x per inch of aperture) and a 0.32mm exit pupil (about 1/75th of an inch across). Operating in this range generally requires exceptional seeing conditions and a very experienced observer. Using this 2.58mm eyepiece with the longer focal lengths of catadioptric telescopes is usually self-defeating, as the images will almost invariably be too dim to be useful. Also, the limited eye relief will restrict its use for observers who must wear eyeglasses due to severe astigmatism.
|
| | Customers who bought this item also bought these items:
|
|
Home | How to pick a telescope | Telescopes | Accessories | New Products | Used & Demo / Special Sales | Binoculars & Spotting Scopes |
Link Support
Terms of Sale | PRIVACY POLICY 7/1/2004 | Fine Print
Toll-Free Telephone Astronomics: 800-422-7876; Christophers, Ltd.: 800-356-6603
Alternate Telephone: 405-364-0858 24 Hour Fax Line: 405-447-3337
Telephone Hours: Monday 8 AM - 6 PM CST
Tuesday-Friday 8 AM - 8 PM CST
Saturday Noon - 5 PM CST
Store Hours: Monday-Friday 9 AM - 5 PM CST
Saturday Noon - 5 PM CST
Astronomics / Christophers, Ltd.
680 S.W. 24th Ave.
Norman, OK, 73069
© 2012 by Ad-Libs Advertising, Inc. All rights reserved
|
Printer friendly version
Email page link to a friend
Do you have a question about this product?
