Orion 100 EQ - Manual (Page 9)

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6. Look through the polar finder at a distant object (during the
day) and center it in 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 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 pro-
cedure 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
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, figure the dif-
ference 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, 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, 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°, the closest stan-
dard 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 clos-
est 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 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 tri-
pod. 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.
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 astrophotog-
raphy 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.
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. The Dec. slow-motion control is not
needed for tracking. Objects will appear to move faster at
higher magnifications, because the field of view is narrower.
Optional Motor Drive
Optional DC motor drive systems can be mounted on the
AstroView 100 EQ’s equatorial mount to provide hands-free
tracking. Objects will then remain stationary in the field of view