Telescope Basics 27
1. Orient the telescope so that the polar axis is pointing as close to true north as possible. (The fork arms
indicate which direction the polar axis is pointing.) You can use a land mark that you know faces north
to get you in the general direction.
2. Shim the legs until the cross level bubbles indicate the mount is level.
3. Adjust the wedge in altitude until the latitude indicator points to the latitude of the site from which you
are observing.
4. Insert a low power eyepiece (i.e., one with a large focal length 30mm) into the telescope to give you the
widest field possible.
5. Turn the clock drive on.
6. Loosen the right ascension and declination clamps and point the telescope at the desired target. The
Moon or one of the brighter planets is an ideal first target.
7. Locate the object in the finder, center it, and then look through the telescope.
8. Turn the focus knob until the image is sharp.
Take your time and study your subject. If observing at the Moon, look for small details in the craters.
That’s all there is to using your Celestron Ultima. However, do not limit your view of an object to a single
eyepiece. After a few minutes, try using a different optional eyepiece, a more powerful one. This gives you
an idea of how the field of view changes. Center your target and focus. If observing the Moon you will be
looking at a few craters at one time.
NOTE: If not using the clock drive, the stars will appear to drift out of the field of view. This is due
to the Earth’s rotation. In fact, anything in the sky, day or night, will drift out of the field
unless the telescope has been polar aligned and the clock drive is running. More on this in
the section on “Polar Alignment.”
CALCULATING MAGNIFICATION
You can change the power of your Celestron Ultima telescope just by changing the eyepiece (ocular).
Eyepieces are an optional accessory that can be purchased through Celestron. See the section “Optional
Accessories” in this manual for further information.
To determine the magnification of your Celestron Telescope, simply divide the focal length of the telescope
by the focal length of the eyepiece used. In equation format, the formula looks like this:
Let’s say, for example, that you are using a 26mm eyepiece. To determine the magnification you simply
divide the focal length of your Celestron Telescope (let us use the Ultima 11 which has a focal length of
2800mm) by the focal length of the eyepiece (26mm). Dividing 2800 by 26 yields a magnification of 108
power.
Although the power is variable, each instrument under average skies 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
Celestron Ultima 11 is 11" in diameter. Multiplying 11 by 60 gives a maximum useful magnification of 660
power. 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 is 220 to 385 times for the Ultima 11 and 185 to 324 for the Ultima
9
1
/
4.
DETERMINING FIELD OF VIEW
To Next Page
Loading...
