9
that is cast into the mount (located directly below the large
thumbscrew; see Figure 3). Retighten the thumbscrew.
2. Rotate the date circle until the “0” line on the meridian
offset scale lines up with the time meridian indicator mark.
The meridian offset scale is printed on the inner circumfer-
ence of the date circle, and is labeled “E20” to “W20”. The
time meridian indicator mark is an engraved line on the
exterior of the polar finder’s housing. It is on the “ring” of
the housing that is closest to the date circle.
3. The R.A. setting circle is labeled in hours, from “0” to “23”
(military time). For Northern Hemisphere observers, refer
to the top numbers on the setting circle. Each small line
represents 10 minutes of R.A. The date circle is labeled
from “1” to “12,” with each number representing a month of
the year (“1” is January, “2” is February, etc.). Each small
line represents a two-day increment.
4. Loosen the R.A. lock lever and rotate the mount about the
R.A. axis until the March 1 indicating mark (the long line
between the “2” and the “3”) on the date circle lines up with
the 4 PM mark (the long line above the “16”) on the R.A.
setting circle. You may find it convenient to remove both the
counterweights and the telescope optical tube to do this.
5. Now, loosen the three thumbscrews on the polar finder
housing and rotate the polar finder so the small circle where
Polaris will be centered is located straight down from the
intersection of the crosshairs. Retighten the thumbscrews.
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 position 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
further 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 thumb-
screws on the housing to redirect the crosshairs of the
polar finder to the apparent center of this circular path.
Repeat this procedure 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
finder from getting bumped, which could knock it out of align-
ment.
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 figure
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 continental 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 standard 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 merid-
ian 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 represents 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 of the mount until the line on the
R.A. setting circle that corresponds to your current local time
lines up with the line on the date circle that indicates the cur-
rent date. If you are on daylight savings time, subtract one
hour from your current local time. For example, if it was
November 1 at 9 PM, you would rotate the telescope in R.A.
until the line above the “21” on the R.A. setting circle lines up
with the long line between the “10” and “11” on the date cir-
cle.
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. Do this by
rotating the tripod left or right, and adjusting the tilt of the R.A.
axis up-or-down with the latitude adjustment T-bolts. When
you are close, you can use the azimuth fine adjustment knobs
(Figure 8) for final positioning. To do this, you will first need to
