User manual CELESTRON 102MM Instruction Manual

[. . . ] 80mm Wide View Spotting Scope (#52260) 102mm Wide View Spotting Scope (#52270) INSTRUCTION MANUAL INTRODUCTION A spotting scope is nothing more than a telescope that is designed to look around the Earth. Unlike astronomical telescopes, which produce inverted or reverted images, spotting scopes produce correctly oriented images. Celestron offers several different models, each of which uses the highest quality optics to produce the best possible images. How to Use this Manual This manual explains the proper use of your Celestron spotting scope --from initial set up to ongoing use. This manual is broken down into several sections. [. . . ] This is derived from multiplying 60 times 4". Although this is the maximum useful magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which for the 102mm Wide View is 80 to 140. 9 Field of View Determining the field of view is important if you want to get an idea of the size of the object you are observing. To calculate the actual field of view, divide the apparent field of the eyepiece (supplied by the eyepiece manufacturer) by the magnification. In equation format, the formula looks like this: Apparent Field of Eyepiece True Field (in degrees) = Magnification Using the example we started with in the previous section, we can determine the field of view using the same 25mm eyepiece. The 25mm eyepiece has an apparent field of view of 50°. Divide the 50° by the magnification, which is 20 power. This yields an actual field of 2. 5°, or two and a half degrees. To convert this to feet at one thousand yards, multiply the actual field of 2. 5° by 52. 5. This gives us a field width of 131 feet at one thousand yards. PHOTOGRAPHY HINTS Metering Celestron spotting scopes have fixed apertures and, as a result, fixed f/ratios. To properly expose your subjects photographically, you need to set your shutter speed accordingly. Most 35mm SLR cameras offer through-the-lens metering which lets you know if your picture is under or overexposed. Adjustments for proper exposures are made by changing the shutter speed. Consult your camera manual for specific information on metering and changing shutter speeds. Reducing Vibration Releasing the shutter manually can cause vibrations, producing blurred photos. To reduce vibration when tripping the shutter, use a cable release. A cable release keeps your hands clear of the camera and lens, thus eliminating the possibility of introducing vibration. Mechanical shutter releases can be used, though air-type releases are best. Blurry pictures can also result from shutter speeds that are too slow. To prevent this, use films that produce shutter speeds greater than 1/250 of a second when hand-holding the lens. If the lens is mounted on a tripod, the exposure length is virtually unlimited. Another way to reduce vibration is with the Vibration Suppression Pads (#93503). These pads rest between the ground and tripod feet. They reduce the vibration amplitude and vibration time. [. . . ] Celestron warrants this telescope to be free from defects in materials and workmanship for two years. Celestron will repair or replace such product or part thereof which, upon inspection by Celestron, is found to be defective in materials or workmanship. As a condition to the obligation of Celestron to repair or replace such product, the product must be returned to Celestron together with proof-of-purchase satisfactory to Celestron. The Proper Return Authorization Number must be obtained from Celestron in advance of return. [. . . ]