Orion ASTROVIEW 9822 - Manual (Page 7)

7
aligning the Polar axis Finder scope
Aligning the polar axis finder scope so that it will accurately
point at the true north pole is a two-step procedure. First, the
polar axis finder must be rotated in its housing so that the
small circle in which Polaris will be placed is in the proper ini-
tial position. Next, the polar axis finder must be adjusted so
that it points directly along the mount’s R.A. axis.
We will start by aligning the polar finder rotationally. Refer to
Figure 3.
1. Loosen the R.A. setting circle lock thumbscrew. Rotate the
R.A. setting circle until the line above the “0” on the setting
circle lines up with the pointed indicator 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 off-
set 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:
1. 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.
2. Rotate the mount 180° about the R.A. axis. Again, it may
be convenient to remove the counterweights and optical
tube first.
3. 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 flash-
light 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 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 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 repre-
sents 5° of longitude. Lines to the left of the “0” on the meridian
offset scale indicate east of the closest standard time meridi-
an, while lines to the right of the “0” indicate west of the clos-
est 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
circle 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.