Tracking Celestial Objects - Levenhuk Skyline PLUS Serie Guia Del Usuario

After a while you will notice your target drifting slowly North or South depending on the direction of
the pole relative to Polaris. To keep the target in the center of the view, turn only the R.A. slow-motion
control.

Tracking celestial objects

When observing through a telescope, astronomical objects appear to move slowly through the
telescope's field of view. When the mount is correctly polar aligned, you only need to turn the R.A.
slow-motion control to follow or track objects as they move through the field. A R.A. motor drive can
be added to automatically track celestial objects by counteracting the rotation of Earth. If the object is
too faint you may want to use setting circles on an equatorial mount. Setting circles allow you to locate
celestial objects whose celestial coordinates have been determined from star charts.
The telescope's R.A. setting circle is scaled in hours, from 1 to 24, with small lines in between
representing 10 minute increments. The upper set of numbers applies to observations in the Northern
Hemisphere, while the numbers below them apply to observations in the Southern Hemisphere.
Setting (calibrating) the R.A. setting circle: in order to set your Right Ascension circle you must first find
a star in your field of view with known coordinates. A good one would be the 0.0 magnitude star Vega in
the Constellation Lyra. From a star chart we know the R.A. coordinate of Vega is 18h 36m.
Loosen the R.A. and DEC. lock knobs on the mount and adjust the telescope so that Vega is centered in
the field of view of the eyepiece. Tighten the R.A. and DEC. lock knobs to lock the mount in place. Now
rotate the R.A. setting circle until it reads 18h36m. You are now ready to use the setting circles to find
objects in the sky (fig. 13).
A German Equatorial mount has an adjustment, sometimes called a wedge, which tilts the mount's polar
axis so that it points at the appropriate Celestial Pole (NCP or SCP). Once the mount has been polar
aligned, it needs to be rotated around the polar axis only to keep an object centered. Do not reposition
the mount base or change the latitude setting. The mount has already been correctly aligned for your
geographical location (i.e. Latitude), and all remaining telescope pointing is done by rotating the
telescope tube around the polar (R.A.) and declination axes (fig. 14).
A problem for many beginners is recognizing that a polar-aligned, equatorial mount acts like an alt-
azimuth mount which has been aligned to a celestial pole. The wedge tilts the mount to an angle equal
to the observer's Latitude, and therefore it swivels around a plane which is parallel to the celestial
(and Earth's) equator. This is now its "horizon"; but remember that part of the new horizon is usually
blocked by Earth. This new "azimuth" motion is called Right Ascension (R.A.). In addition, the mount
swivels North (+) and South (–) from the Celestial Equator towards the celestial poles. This plus or minus
"altitude" from the celestial equator is called Declination (Dec.).
Now, consider pointing the telescope to the western or eastern horizon. If the counterweight is pointing
North, the telescope can be swiveled from one horizon to the other around the Dec. axis in an arc that
passes through the NCP (any Dec. arc will pass through the NCP if the mount is polar-aligned). It can
be seen then that if the optical tube needs to be pointed at an object north or south of this arc, it
has to be also rotated around the R.A. axis. Pointing in any direction other than due North requires a
combination of R.A. and Dec. positions.
Telescopes with long focal lengths often have a "blind spot" when pointing near the zenith, because
the eyepiece-end of the optical tube bumps into the mount's legs. To avoid this, the tube can be
very carefully slipped up inside the ring clamps. This can be done safely because the tube is pointing
almost vertically, and therefore moving it does not cause a Dec. balance problem. It is very important
to move the tube back to the Dec. balanced position before observing other sky areas.
Something which can also be a problem is that the optical tube often rotates so that the eyepiece,
finderscope and the focusing knobs are in less convenient positions. The diagonal mirror can be rotated
to adjust the eyepiece. However, to adjust the positions of the finderscope and focusing knobs, loosen
the tube rings holding the telescope tube and gently rotate it. Do this when you are oing to observe an
g
area for while, as it is inconvenient to repeat every time you briefly go to a new area.
Finally, there are a few things to consider to ensure that you are comfortable during the viewing
session. First is setting the height of the mount above the ground by adjusting the tripod legs. You must
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