TAL TAL-100RS Service Manual - page 8
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The exposures, which are required for photographing the star fields, are
tenths of minutes without interference of the street lighting. Therefore, for this
period of time one should see to it that the camera follows the sky precisely in
its diurnal rotation. Near the center of the field of view of the camera one
chooses the bright star to which the telescope is pointed. To keep the star on
the reticle cross hairs of the finderscope is the problem for an observer for the
whole period of exposure. As the cross-hairs of the finderscope is not illuminated,
the image of the guide stair should be slightly defocused in order to cross a
light circle of the unsharp image of the star by the cross-hairs and to keep the
star in this position for the period of exposure.
One applies minor corrections for a clockwork drive with the help of
handwheel 4 (fig. 3) keeping the star on the cross hairs for the whole period of
exposure. One corrects the position of the guide star with the micrometer screw
of the declination axis if necessary. To obtain the minimum corrections in
declination the polar axis should be set as precisely as possible to the celestial
pole. One should remember that if the polar axis is set incorrectly, even in the
case when the star image is kept on the cross-hairs, the images of the stars at
the edges of the field of view appear as dashes.
7.3. Telescope and atmospheric conditions
At high magnifications together with the increase of the visible dimensions
of the object the disturbances due to atmosphere are increased. They are
expressed in great blurring of the images of the distant objects, in scintillation
and blurring of the star images.
The observation in the cold seasons is possible when all telescope parts
acquire the ambient temperature. For air circulation inside the telescope tube
there is a hole plugged with a stopper in the cell of the primary mirror. In
operation the stopper should be unscrewed from the cell.
But in observations outdoor the great disturbance of atmosphere may take
place at nights, that lead to bad images of the celestial objects.
It is quite possible that at those nights the observations of the fine details of
the planets and of the Moon are unsuccessful.
It is apparent that the observations with the aid of the telescope through the
window are senseless as the rough surfaces of the window glasses distort the
images.
In case of precipitation and stopping of operation the telescope together
with supply unit must be covered.
Fig. 5
. Accessories:
1 - cap; 2 - eyepiece; 3 - light filter; 4 - wrentch; 5 - napkin; 6 - blind;
7 - reticle; 8 - adapter
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