Seben 1000/90 Manuel Du Propriétaire page 9

1. Once you have found an object in the telescope, turn the focus knob until the image is sharp.
2. To focus on an object that is nearer than your current target, turn the focus knob toward the
eyepiece (i.e., so that the focus tube moves away from the front of the telescope). For more
distant objects, turn the focus knob in the opposite direction.
3. To achieve a truly sharp focus, never look through glass windows or across objects that
produce heat waves, such as asphalt parking lots.
1. When observing with a diagonal, the image will be right side up but reversed from left to right.
2. When observing straight through, with the eyepiece inserted directly into the telescope, the
image will be inverted. Also, the image in the finderscope will be inverted.
The magnification (or power) of a telescope varies depending upon the focal length of the eye-
piece being used and the focal length of the telescope.
To calculate magnification, use the following formula, in which FL = focal length:
FL(telescope)inmm
Magnification =
FL (eyepiece) in mm
CAUTION! Viewing the sun can cause permanent eye damage. Do not view the sun with
this product or even with the naked eye. Never leave a telescope unattended during the
daytime; a child could look at the sun with it and suffer permanent damage to vision.
PREPARING THE TELESCOPE FOR PROJECTING THE SUN ON A SCREEN
CAUTION! Cover the objective lens so no one can look through it.
1. Insert the projection screen rod by sliding it through the opening in the finderscope bracket with
the washer end of rod toward the objective. (The washer acts as a stop, preventing the sun
screen assembly from slipping completely through the finderscope bracket.)
2. If the diagonal is in place, remove it. It will not be used for solar observation.
3. Select the lowest power eyepiece (the one with the highest numerical designation in millime-
ters) and insert it, without the diagonal, into the focus tube.
4. Select the black plate of the sun projection assembly. Slip it onto the rod, position it near the
eyepiece so that the hole is centered with the lens of the eyepiece and lock it in place. This
plate shades the white projection screen which will be put in place in a later step. The tele-
scope is now ready to observe the sun.
1. Point the telescope in the general direction of the sun without looking through it or the finder-
scope. Looking at the shadow of the telescope on the ground will help in aiming it.
2. Hold the white plate a few inches behind the finderscope eyepiece and move the telescope
gently until you see the sun projected on the white plate. You will see a round "picture" of the
sky with the sun somewhere in the "picture". Move the telescope, using the flexible control
cables until the sun is centered in this projected image of the sky.
3. Next, slip the white plate into place on the sun projection assembly rod. Position it directly in
line with the telescopeʼs eyepiece and lock it in place.
4. Use the flexible control cables to make any small corrections necessary to center the sunʼs
image on the white screen.
5. Focus the sunʼs image on the white screen using the focus knob.
6. The projected image will show sunspots, the "rice-grain" structure of the solar disk, and that the
sun is brighter at the center of the disk than at the edge.
FOCUSING
IMAGE ORIENTATION
MAGNIFICATION
SOLAR OBSERVATION
OBSERVING THE SUN
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