By William Paolini
A beneficial reference that fills a couple of niches together with that of a dealers advisor, technical table reference and observers box advisor. It files the prior marketplace and its evolution, correct as much as the current day. as well as beautiful to useful astronomers - and probably saving them cash - it truly is valuable either as a historic reference and as an in depth evaluate of the present industry position for this bustling astronomical client product.
What distinguishes this booklet from different guides on astronomy is the involvement of observers from all features of the astronomical group, and in addition the most important brands of kit. It not just catalogs the technical points of the various glossy eyepieces but additionally files beginner observer reactions and impressions through the years, utilizing many alternative eyepieces.
Eyepieces are the main talked-about add-ons and collectible goods to be had to the beginner astronomer. No different merchandise of apparatus instructions such lively debate, or has developed into this kind of impressive array of varieties and services. deciding on and utilizing Astronomical Eyepieces presents an enormous volume of reference fabric to indicate readers in the direction of the easiest buys and the appropriate eyepieces for other kinds of looking at.
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Extra info for Choosing and Using Astronomical Eyepieces
Com. Illustration by the author) Apparent Field of View (AFOV) 25 Aberrations (Including Distortions) Each eyepiece design corrects for aberrations differently than any other design, whether the design is as simple as a common Plössl or as complex as a name brand ultra-wide ﬁeld. The degree to which these aberrations will be corrected may also vary with the focal ratio of the telescope. Therefore, understanding the strengths and weaknesses of an eyepiece’s optical design when used in different telescopes enables the experienced observer to make better decisions on appropriate eyepieces for appropriate telescopes.
What these observers do not realize is that the available range of focal lengths that an eyepiece line can accommodate is often directly related to the optical design type used by that eyepiece line. As an example, the time-honored Erﬂe design, which observers have been using for many decades, is rarely ever seen in a focal length shorter than 16 mm. Similarly, the very popular Tele Vue Panoptic line of 68° AFOV eyepieces is only available in focal lengths as short as 15 mm. The reason that shorter focal lengths are not produced for these designs is that at focal lengths shorter than approximately 15 mm, the resulting eye relief of these designs becomes too short Optical Design Characteristics 17 to be effectively used by an observer.
Fig. 8 Examples of size and weight variations of eyepieces. 40 mm Pentax XW (left) vs. 40 mm Meade 3000 Plössl (right) (Image by the author) A usage area where the size of an eyepiece can be critical is in the width of the housing. This becomes important if the observer plans to choose eyepieces for use in a binoviewer. If the eyepieces are too wide, then an observer may not be able to move the two eyepieces close enough to each other in the binoviewer so that their eyes can be positioned over the center of the eye lenses.