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Owner's of the Celestron Telescope 52291 gave it a score of 0 out of 5. Here's how the scores stacked up:
between 20 to 35 power for every inch of aperture which is 100 to 175 times for
the C5.
Determining the field of view is important if you want to get an idea of the
angular 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 (in degrees)
True Field = ————————————————
Magnification
As you can see, before determining the field of view, you must first calculate the
magnification. Using the example in the previous section, we can determine the
field of view using the same 26mm eyepiece. The 25mm Plossl eyepiece has an
apparent field of view of 52°. Divide the 52° apparent field by the magnification,
which is 50 power. This yields an actual field of 1.04°.
To convert degrees to feet at 1,000 yards, which is more useful for terrestrial
observing, simply multiply by 52.5. Continuing with our example, multiplying
the angular field 1.04° by 52.5 produces a linear field width of 54.6 feet at a
distance of one thousand yards.
The apparent field of each eyepiece that Celestron manufactures is found in the
Celestron Accessory Catalog (#93685).
When working with any optical instrument, there are a few things to remember to
ensure you get the best possible image.
• Never look through window glass. Glass found in household windows is
optically imperfect and, as a result, may vary in thickness from one part of a
window to the next. This inconsistency can and will affect the ability to focus
your spotting scope. In most cases you will not be able to achieve a truly sharp
image. In some cases, you may actually see a double image.
• Never look across or over objects that are producing heat waves. This includes
asphalt parking lots on hot summer days or building rooftops.
• Hazy skies, fog, and mist can also make it difficult to focus when viewing
terrestrially. The amount of detail seen under these conditions is greatly reduced.
Also, when photographing under these conditions, the processed film may come
out a little grainier than normal with lower contrast.
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