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If you are an avid visual astronomer, it may come as little surprise to find that colored filters make a world of difference to your observing clarity, and their use brings out detail from the subtle shadings found on Solar System objects.

Anyone with even a casual interest in astronomy should own a good pair of binoculars. Even avid amateurs with a houseful of telescopes will have at least one pair of binoculars at the ready. And for some activities, binoculars will be all you really need for a lifetime of applications.

This chapter will introduce you to the astronomical eyepiece—its historical beginnings, basic function, physical construction, optical construction, and optical design characteristics. You will also gain a deeper understanding of some of the more technical aspects of eyepiece performance parameters related to focal length, apparent field of view, eye relief, exit pupil, stray light control, and optical aberrations.

These use extra low-dispersion glass, are parfocal, and have an outstanding build quality. This eyepiece line is within the following competition class of eyepieces with similar specifications and performance: Antares Elite, Baader Eudiascopic, Bresser 60° Plossl, Celestron Ultima, Kasai Astroplan, Meade Series 4000 Super Plossl (pre-1994, smooth sided, five-elements), Meade Series 5000 Super Plossl, Orion Ultrascopic, Parks Gold Series Plossl.

In the marketplace today, there are literally many hundreds of eyepiece lines from which to choose. How can one possibly navigate such a large marketplace and ever hope to make a good decision? The answer is, of course, to arm yourself first with knowledge. When considering the choice and use of an eyepiece, it helps to first consider

Planetary nebulae are one of the most varied groups of objects to observe. Many can be seen in relatively small telescopes, while others of their class require larger apertures and specific observing techniques involving filters. They range in magnitude from 7.5 for the Dumbbell Nebula to 14th or 18th magnitude for some of the fainter Abell or P-K catalogue members. Although several astronomical objects also have wide ranges of magnitudes, planetaries have something special about them in their variation in morphology, brightness, size and observability under different conditions.

This chapter includes a discussion of focusers that can be built or purchased, eyepiece types available on the Internet or which can be salvaged from other equipment, focal-length extender devices, and finder telescopes.

The most spectacular comets are those which are visible to the unaided eye. The purpose of this Chapter is to describe the types of comet observations which one can do with the unaided eye or with binoculars. First, a description of the human eye and its capabilities is presented. This is followed by an overview of binoculars. Finally, I discuss techniques for observing comets and recording information, such as coma brightness, the degree of condensation (DC) and estimating atmospheric transparency.

What we know about the universe is gleaned mostly from our local surroundings. The detection of radiation from space is needed in order to test the universality of locally derived descriptions of the physical behavior of matter and energy. But, quite apart from any utilitarian motive, we also want to more fully comprehend the physical nature of the universe. Therefore, we have to be serious about doing it correctly: it is important to ensure that astronomical detectors are indeed measuring the radiation from a distant target and not from the telescope,1 the dome, or the sky around the source. Moreover, it should be done in the most efficient way; there is no point in using an apparatus that requires a hundred hours of observation time when another technique or device will provide the same information in one hour. Practical considerations in the real world sometimes require us to use what is available instead of what we would like to use, but this does not remove the scientific imperative to use the best apparatus for the purpose. In this exercise, we examine the purposes and capabilities of our basic instruments and the uses to which they can be put.

A Galilean telescope in its simplest form is a two element system consisting of a positive lens as an objective and a negative lens as an eyepiece. The system is restricted to lower magnifications and smaller fields of view in comparison with a Keplerian telescope. The image through the system, however, is always erect permitting its use for distance viewing for partially sighted patients. Other optical factors besides magnification and field of view that need to be considered include exit pupil size, focus adjustability, vertex distance, and image quality in terms of color and brightness. Such non optical factors as weight, portability, ease of use, appearance and cost are also influencing variables [1]. In this overview on the clinical use of low power telescopes in the examination room, only a few properties will be examined. The use of a low power full-field telescope in subjective and objective refractions will be discussed. Magnification through a telescope will also be elaborated upon.