20
6. When the download is complete, the Firmware Loader
will display “Update Complete”.
The firmware in the computerized GoTo hand controller has
now been updated. You can click on the “HC Version” button to
confirm the new version number of the firmware (and possibly
the database, but the hardware version will not change with
internet updates).
Note: If the error message “Can not connect to a SynScan
hand control” appears on your computer, check all cable
connections. Also, try closing all other computer pro-
grams that might be attempting to use the COM port.
Note: If the error message “Firmware update failed...”
appears on your computer, remove the power plug from
the hand controller, and then reconnect it. Now, repeat
the firmware update procedure.
By default, the data communication rate between the GoTo
hand controller and the computer is 115kbps. The RS-232
port on some PCs may not support this high data transfer
rate. If the firmware update procedure fails after a few tries,
try reducing the data transfer rate by pressing the SETUP but-
ton on the hand controller. This will reduce the data transfer
rate to 9.6kbps. The controller’s LCD screen will show “Lo” in
the lower right hand corner to indicate the lower transfer rate
setting. The firmware update procedure remains the same
except it will take much longer for the firmware to load into the
hand controller.
8. Collimating the Optical System
To get the sharpest images, your telescope’s optical sys-
tem must be in precise alignment. The process of aligning
the primary and secondary mirrors with each other and with
the mechanical axis of the telescope is called collimating.
Collimating is relatively easy to do and can be done in day-
light or at night.
Because the primary mirror is shipped separately from the
optical tube, the telescope’s optics must be collimated before
it can be used. Most of the adjustments will be to the tilt of the
primary mirror, as the secondary mirror has been pre-aligned
at the factory. It is also good idea to check the collimation
(optical alignment) of your telescope before each observing
session and make any necessary adjustments.
To check collimation, remove the eyepiece and look down the
focuser drawtube. You should see the secondary mirror cen-
tered in the drawtube, as well as the reflection of the primary
mirror centered in the secondary mirror, and the reflection of
the secondary mirror (and your eye) centered in the reflection
of the primary mirror, as depicted in Figure 25a. If anything
is off-center, as in Figure 25b, proceed with the following col-
limation procedure.
The Collimation Cap and Mirror Center Mark
Your XTg comes with a collimation cap. This is a simple cap
that fits on the focuser drawtube like a dust cap, but has a hole
in the center and a reflective inner surface. The cap helps cen-
ter your eye so that collimating is easier to perform. Figures
25b-e assume you have the collimation cap in place.
As an additional aid in collimating, the primary mirror of the
XTg has a tiny adhesive ring marking its exact center. This
center ring will not affect the images you see when observ-
ing with the telescope in any way (since it lies directly in the
shadow of the secondary mirror), but it will greatly facilitate
collimating when using the supplied collimation cap or other,
more sophisticated collimation devices, such as the Orion
LaserMate Laser Collimator.
Preparing the Telescope for Collimating
Once you get the hang of collimating, you will be able to do it
quickly even in the dark. For now, it is best to collimate in day-
light, preferably in a brightly lit room and aimed at a white wall.
It is recommended that the telescope tube be oriented hori-
zontally. This will prevent any parts from the secondary mirror
from falling down onto the primary mirror and causing damage
if something comes loose when you are making adjustments.
Place a sheet of white paper inside the optical tube directly
opposite the focuser. This will provide a bright “background”
when viewing into the focuser. When properly set up for col-
limation, your telescope should resemble Figure 26.
Aligning the Secondary Mirror
With the collimation cap in place, look through the hole in the
cap at the secondary (diagonal) mirror. Ignore the reflections
for the time being. The secondary mirror itself should be cen-
tered in the focuser drawtube. If it isn’t, as in Figure 21b, its
position must be adjusted. This positional adjustment of the
secondary mirror will rarely, if ever, need to be done.
To adjust the secondary mirror left-to-right in the focuser draw-
tube, use the included 2mm hex key to loosen the three small
alignment setscrews in the center hub of the 4-vaned spider
several turns. Now, grasp the mirror to prevent it from rotating
(be careful not to touch the surface of the mirror), while turn-
ing the center screw with a Phillips head screwdriver (Figure
27). Turning the screw clockwise will move the secondary mir-
ror toward the front opening of the optical tube, while turning
the screw counter-clockwise will move the secondary mirror
toward the primary mirror. When the secondary mirror is cen-
tered left-to-right in the focuser drawtube, rotate the second-
ary mirror holder until the reflection of the primary mirror is as
centered in the secondary mirror as possible. It may not be
perfectly centered, but that is OK for now. Tighten the three
small alignment setscrews equally to secure the secondary
mirror in that position.
Note: When making these adjustments, be careful not to
stress the spider vanes or they may bend.
The secondary mirror should now be centered in the focuser
drawtube. Now we will shift our attention to the reflections
within the secondary mirror in order to properly adjust the tilt
of the secondary mirror. Adjusting the tilt of the secondary