Orion ASTROVIEW 9822 - Manual (Page 8)

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For example, if it was November 1 at 9 PM, standard time, you
would rotate the telescope in R.A. until the line above the “21”
(9 P.M.) on the R.A. setting circle lines up with the long line
between the “10” and “11” on the date circle. The long line
indicates the first day of the higher numbered month, i.e. the
line between “10” and “11” marks November 1st.
Finally, look through the polar alignment finder scope while
shining a red flashlight at an angle down the front opening of
the R.A. axis, and center Polaris in the small circle. Adjust the
tilt of the altitude up-or-down with the latitude adjustment
T-bolts and use the azimuth fine adjustment knobs (Figure 8)
for final positioning. To do this, you will first need to loosen the
big tripod attachment knob directly underneath the base of the
equatorial mount. The fine adjustment knobs work by loosen-
ing one and then tightening the other. Once Polaris is centered
in the small circle, retighten the tripod attachment knob to
firmly secure the mount and tripod. If the fine adjustment
knobs do not allow the mount to move far enough to center
Polaris, you will need to rotate the entire tripod left or right to
get it within the fine adjustment’s range.
The telescope is now accurately polar aligned, and can be
used for advanced observational applications, such as astro-
photography or precise use of the manual setting circles. As
mentioned before, only move the telescope along the R.A.
and Dec. axes; if you move the tripod, or change the tilt of the
equatorial mount, you will need to polar align again.
Remember, accurate polar alignment is not needed for casual
visual observing. Most of the time, approximate polar align-
ment, as outlined previously, will suffice.
use of the r.a. and Dec.
slow-Motion control cables
The R.A. and Dec. slow-motion control cables allow fine
adjustment of the telescope’s position to center objects within
the field of view. Before you can use the cables, you must
manually “slew” the mount to point the telescope in the vicinity
of the desired target. Do this by loosening the R.A. and Dec.
lock levers and moving the telescope about the mount’s R.A.
and Dec. axes. Once the telescope is pointed somewhere
close to the object to be viewed, retighten the mount’s R.A.
and Dec. lock levers.
The object should now be visible somewhere in the tele-
scope’s finder scope. If it isn’t, use the slow-motion controls to
scan the surrounding area of sky. When the object is visible in
the finder scope, use the slow-motion controls to center it.
Now, look in the telescope’s eyepiece. If the finder scope is
properly aligned, the object should be visible somewhere in
the field of view. Once the object is visible in the eyepiece, use
the slow-motion controls to center it in the field of view.
tracking celestial objects
When you observe a celestial object through the telescope,
you’ll see it drift slowly across the field of view. To keep it in the
field, if your equatorial mount is polar aligned, just turn the
R.A. slow-motion control cable clockwise. The Dec. slow-
motion control cable is not needed for tracking. Objects will
appear to move faster at higher magnifications, because the
field of view is narrower.
optional Motor Drives for automatic tracking
An optional DC motor drive can be mounted on the R.A. axis
of the equatorial mount to provide hands-free tracking. Objects
will then remain stationary in the field of view without any
manual adjustment of the R.A. slow-motion control cable.
understanding the setting circles
The setting circles on an equatorial mount enable you to
locate celestial objects by their “celestial coordinates”. Every
object resides in a specific location on the “celestial sphere”.
That location is denoted by two numbers: its right ascension
(R.A.) and declination (Dec.). In the same way, every location
on Earth can be described by its longitude and latitude. R.A. is
similar to longitude on Earth, and Dec. is similar to latitude.
The R.A. and Dec. values for celestial objects can be found in
any star atlas or star catalog.
The R.A. setting circle is scaled in hours, from 1 through 24,
with small marks in between representing 10-minute incre-
ments (there are 60 minutes in 1 hour of R.A.). The upper set
of numbers apply to viewing in the Northern Hemisphere,
while the numbers below them apply to viewing in the Southern
Hemisphere. The location of the R.A. coordinate indicator
arrow is shown in Figure 3.
The Dec. setting circle is scaled in degrees, with each mark
representing 2° increments. Values of Dec. coordinates range
from +90° to -90°. The 0° mark indicates the celestial equator.
When the telescope is pointed north of the celestial equator,
values of the Dec. setting circle are positive; when the tele-
scope is pointed south of the celestial equator, values of the
Dec. setting circle are negative.
So, the coordinates for the Orion Nebula listed in a star atlas
will look like this:
R.A. 5h 35.4m Dec. - 5° 27'
That’s 5 hours and 35.4 minutes in right ascension, and -5
degrees and 27 arc-minutes in declination (there are 60 arc-
minutes in 1 degree of declination).
Before you can use the setting circles to locate objects, the
mount must be well polar aligned, and the R.A. setting circle
must be calibrated. The Dec. setting circle has been calibrated
at the factory, and should read 90° whenever the telescope
optical tube is parallel with the R.A. axis.
calibrating the right ascension setting circle
1. Identify a bright star in the sky near the celestial equator
(Dec. = 0°) and look up its coordinates in a star atlas.
2. Loosen the R.A. and Dec. lock levers on the equatorial
mount, so the telescope optical tube can move freely.
3. Point the telescope at the bright star whose coordinates
you know. Lock the R.A. and Dec. lock levers. Center the
star in the telescope’s field of view with the slow-motion
control cables.
4. Loosen the R.A. setting circle lock thumbscrew (see Figure
3); this will allow the setting circle to rotate freely. Rotate the
setting circle until the arrow under the thumbscrew indicates
the R.A. coordinate listed in the star atlas for the object. Do
not retighten the thumbscrew when using the R.A. setting