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Why Binoculars?
Abstract
Amateur astronomers usually view small- and medium-aperture (50–70 mm) binoculars either as an inexpensive “entry level” instrument to the hobby or as a useful accessory to a more experienced observer’s “main” instrument, a telescope. There is a great deal of justification for this. Binoculars do indeed make excellent starter instruments for new observers, especially those of limited financial means. A medium-aperture binocular of reasonable quality is not only less expensive than the cheapest useful astronomical telescopes, but it is also much more intuitive to use, easier to set up, more portable, and has more obvious uses outside astronomy, for example, bird-watching or horse racing. It also enables the new observer to engage in useful observing programs, such as the Society for Popular Astronomy’s variable star program.
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Entirely updated to cover the latest technology, this second edition gives optical designers and optomechanical engineers a thorough understanding of the principal ways in which optical components--lenses, windows, filters, shells, domes, prisms, and mirrors of all sizes--are mounted in optical instruments. Along with new information on tolerancing, sealing considerations, elastomeric mountings, alignment, stress estimation, and temperature control, two new chapters address the mounting of metallic mirrors and the alignment of reflective and catadioptric systems. The updated accompanying CD-ROM offers a convenient spreadsheet of the many equations that are helpful in solving problems encountered when mounting optics in instruments. © 2008 Society of Photo-Optical Instrumentation Engineers. All rights reserved.
An easy-to-use book that takes the math and the mystery out of optical design. Uses a grtaphics-oriented approach, making optical design techniques easy to understand through hundreds of detailed diagrams. A comprehensive one-stop resource for optical engineers, designers, lens designers, and others, both experts and beginners.
To measure the dark-adapted pupil diameter of normal research participants in their second through ninth decades of life using the NeurOptics pupillometer (Neuroptics Inc).
Individuals aged 18 to 80 years with no history of eye disease or injury, intraocular surgery, or use of systemic antihistamines or opiates were recruited. After 2 minutes of adaptation at 1 lux illumination, the right dark-adapted pupil diameter was measured using the NeurOptics pupillometer, with accommodation controlled by distance fixation. The NeurOptics pupillometer reported a mean dark-adapted pupil diameter and a standard deviation of the mean, which were analyzed as a function of age-decade.
Two-hundred sixty-three individuals participated. For participants aged 18 to 19 years (n=6), the mean dark-adapted pupil diameter was 6.85 mm (range: 5.6 to 7.5 mm); 20 to 29 years (n=66), 7.33 mm (range: 5.7 to 8.8 mm); 30 to 39 years (n=50), 6.64 mm (range: 5.3 to 8.7 mm); 40 to 49 years (n=51), 6.15 mm (range: 4.5 to 8.2 mm); 50 to 59 years (n=50), 5.77 mm (range: 4.4 to 7.2 mm); 60 to 69 years (n=30), 5.58 mm (range: 3.5 to 7.5 mm); 70 to 79 years (n=6), 5.17 mm (range: 4.6 to 6.0 mm); and 80 years (n=4), 4.85 mm (range: 4.1 to 5.3 mm). These values were consistent with studies using infrared photography. The standard deviation was >0.1 mm in 10 (3.8%) participants, all of whom were younger than 55 years.
The dark-adapted pupil diameter is an important clinical variable when planning refractive surgery. Surgeons can compare a patient's dark-adapted pupil diameter with the results of this population study to identify outlier measurements, which may be erroneous, and repeat testing prior to surgery.
The Backyard Astronomer’s Guide
- T Dickinson
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Touring the Universe through Binoculars
- Philip S Harrington
- PS Harrington