Your First Look; Daytime Observing - Celestron Firstscope 80 AZ Instruction Manual

Calculating
Magnification
Your First Look
WARNING!
You can change the power of your Celestron telescope just by changing the
eyepiece (ocular). To determine the actual magnification with any given eyepiece,
simply divide the focal length of the telescope by the focal length of the eyepiece.
In equation format, the formula looks like this:
Focal Length of Telescope (mm)
Magnification = -
Focal Length of Eyepiece (mm)
Let's take an example (using the 80mm AZ) to see how this formula works. Let's say
you're observing with a 20mm eyepiece. To determine the magnification, you
would simply divide the focal length of the telescope (900mm) by the focal length
of the eyepiece. Since we are using a 20mm eyepiece for our example, you would
divide 900 by 20. This yields a magnification of 45 power.
Although the power is variable, each instrument has a limit to the highest useful
magnification. The general rule is that 60 power can be used for every inch of
aperture. For example, the Firstscope 80 AZ is 3.14" (80mm) in diameter. Multiply¬
ing 3.14" by 60 gives a maximum useful magnification of 188 power. Although this
is the maximum useful magnification, most observing is done in the range of 10 to
30 power for every inch of aperture which is about 30 to 100 power for the
Firstscope 80 AZ.
Higher powers (more than 60x the diameter) can be used for looking at super enlarged
images of the planets and the moon, but the images will be dark with little contrast,
and somewhat fuzzy.
With the telescope fully assembled and all the accessories attached, you are ready
for your first look. Your first look should be done in the daytime when it will be
easier to locate the locking clamps and adjustment knobs. This will help to familiar¬
ize you with your telescope, thus making it easier to use at night.
Daytime Observing
1. Find a distant object that is fairly bright.
2. Insert the standard 20mm eyepiece into the diagonal.
3. Locate the object in the finderscope.
4. Use the slow motion knobs to center the object in the field of the finder.
5. Look through the main optics and the object will be there (if you aligned the
Star Pointer first).
Try using different optional eyepieces to see how the field changes with various
magnifications.
NEVER POINT YOUR TELESCOPE AT THE SUN UNLESS Y OU HAVE THE
PROPER SOLAR FILTER. PERMANENT AND IRREVERSIBLE EYE DAM¬
AGE MAY RESULT AS WELL AS DAMAGE TO YOUR TELESCOPE. ALSO,
NEVER LEAVE YOUR TELESCOPE UNATTENDED DURING A DAYTIME
OBSERVING SESSION, ESPECIALLY WHEN CHILDREN ARE PRESENT.
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