9
Star Testing
A star test can be performed to confirm the collimation accu-
racy of the telescope. The adjustment procedure on the tele-
scope is the same as described above; testing, however, will
be done in the night sky using a real star and you will not use
the Cheshire eyepiece.
Choose a star close to the zenith (straight overhead) rath-
er than at the horizon to minimize atmospheric distortions.
Using Polaris as your target star can be helpful as minimal
drift adjustments will be required.
Do not use a star diagonal while performing this procedure.
Rather, place an eyepiece directly into the 1.25" adapter in
the focuser. It should be an eyepiece that provides moder-
ate to high magnification. You may need to add all three of
the extension rings in front of the focuser to be able to reach
focus. Center the star in the field of view. Slowly de-focus the
image with the focusing knob until you can see a series of
concentric diffraction rings form around the dark disk in the
center. That dark disk is the shadow of the secondary mir-
ror. In a well collimated telescope, the diffraction rings should
appear round and concentric, with the dark disk exactly in
the center (
Figure 12). If the dark central disk is off center,
the scope is out of collimation. Adjust the collimation of the
secondary mirror and, only if necessary, the primary mirror
while monitoring the defocused star until the dark central disk
is exactly centered in the diffraction rings.
NOTE: It is important when checking or adjusting the col-
limation using a star, that the star be positioned in the
center of the eyepiece’s field of view. If it isn’t, the optics
will always appear out of collimation, even though they
may be perfectly aligned! It is critical to keep the star
centered, so over time you may need to make slight cor-
rections to the telescope’s position.
Care and Cleaning of the
Optics
Do not disassemble the Ritchey-Chrétien for any reason,
including to clean the mirror. A small amount of dust and par-
ticulates on the mirror’s surface will not affect performance. In
the event internal cleaning is necessary the telescope should
be shipped to Orion Telescopes and Binoculars for service.
This telescope does not contain user-serviceable parts and
disassembly of the components will void the warranty. When
not in use, please use the supplied dust cap(s) to keep dust
and particulates out of the tube and off the optics.