9
The polar axis finder scope is now properly set in its initial
position. Next, we must align it so that it is exactly parallel to
the mount’s R.A. axis:
6. Look through the polar finder at a distant object (during
the day) and center it on the crosshairs. You may need to
adjust the latitude adjustment T-bolts and the tripod posi-
tion to do this.
7. Rotate the mount 180° about the R.A. axis. Again, it may
be convenient to remove the counterweights and optical
tube first.
8. Look through the polar finder again. Is the object being
viewed still centered on the crosshairs? If it is, then no fur-
ther adjustment is necessary. If not, then look through the
polar finder while rotating the mount about the R.A. axis.
You will notice that the object you have previously centered
moves in a circular path. Use the three thumbscrews on
the housing to redirect the crosshairs of the polar finder to
the apparent center of this circular path. Repeat this proce-
dure until the position that the crosshairs point to does not
rotate off-center when the mount is rotated in R.A. Once
this is accomplished, retighten the thumbscrews.
The polar axis finder scope is now ready to be used. When not in
use, replace the plastic protective cover to prevent the polar find-
er from getting bumped, which could knock it out of alignment.
Using the Polar Axis Finder
When using the polar finder in the field at night, you will need
a red flashlight to illuminate the finder’s reticle. Shine the
flashlight at an angle into the front opening in the R.A. axis.
Do not shine it directly into the opening, or the light will be too
bright, and you will also obstruct the view of the polar finder. It
may be helpful to have a friend hold the flashlight while you
look through the polar finder.
For most accurate polar alignment, you will need to know the
approximate longitude of your observing site. This information
can be obtained by looking at a local map. Now, you must fig-
ure the difference between the longitude of your observing
site and the closest standard time meridian. The standard
time meridians are 75°, 90°, 105°, and 120° for the 48 conti-
nental states (150° and 165° for Hawaii and Alaska). Choose
the standard time meridian that is closest in value to your
local longitude, and then calculate the difference.
If your local longitude has a value less than the closest stan-
dard time meridian, then you are east of the standard time
meridian by the calculated amount. If your local longitude has
a value greater than the closest standard time meridian, then
you are west of the standard time meridian by the calculated
amount. For example, if you are in Las Vegas, which has a
longitude of 115°, then the closest standard time meridian is
120°. The difference between these two numbers is 5°. Since
Las Vegas’ longitude value is less than the standard time
meridian value, you are 5° east of the closest time meridian.
Take your calculated difference from the closest standard
time meridian and rotate the date circle so that the meridian
offset scale line that corresponds to your calculated difference
lines up with the engraved time meridian indicator mark on the
polar finder housing. Each line of the meridian offset scale rep-
resents 5° of longitude. Lines to the left of the “0” on the
meridian offset scale indicate east of the closest standard time
meridian, while lines to the right of the “0” indicate west of the
closest standard time meridian. Continuing with the prior
example of observing in Las Vegas, you would rotate the date
circle so that the first line to the left of the “0” on the meridian
offset scale lines up with the time meridian indicator mark.
Make sure that the "0" mark on the R.A. setting circle lines up
with the pointed indicator cast into the mount, and that the
large thumbscrew just above it is tightened. Now, rotate the
mount about the R.A. axis until the line on the R.A. setting cir-
cle that corresponds to your current local time lines up with
the line on the date circle that indicates the current date. If you
are on daylight savings time, subtract one hour from your cur-
rent local time. 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. When done, 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 tri-
pod left or right to get it within the fine adjustment’s range.
Once Polaris is centered in the small circle, you are done. The
telescope is now accurately polar aligned, and can be used
for advanced observational applications, such as astropho-
tography 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 casu-
al visual observing. Most of the time, approximate polar
alignment, 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 vicini-
ty 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 some-
where close to the object to be viewed, retighten the mount’s
R.A. and Dec. lock levers.
