Orion SIRIUS 9995 - Manual (Page 4)

4
the azimuth adjustment knobs on the equatorial mount in
order to fit the mount onto the tripod head.
3. Thread the central support shaft up through the tripod
head and into the bottom of the equatorial mount until
tight. Use the upper knob on the central support shaft to
do this. The equatorial mount should now be firmly con-
nected to the tripod.
4. Remove the knob and washer from the bottom of the
center support shaft. Slide the tripod support tray up the
bottom of the central support shaft until the three tray
arms are touching the legs of the tripod. The flat side of
the support tray should be facing up. Make sure the “V” of
each tray arm is against a tripod leg. Place the washer on
the center support shaft against the tray, and follow it by
threading the knob all the way up the center support shaft
until it is tight against the tray. The tripod support tray pro-
vides additional stability for the tripod, and holds up to five
1.25" eyepieces and two 2" eyepieces.
5. Loosen the counterweight shaft lock lever and fully extend
the counterweight shaft. Retighten the lock lever.
6. Remove the knurled “toe saver” retaining screw on the bot-
tom of the counterweight shaft and slide the counterweight
onto the shaft. Make sure the counterweight lock knob is
adequately loosened to allow the counterweight shaft to
pass through the hole. Position the counterweight about
halfway up the shaft and tighten the lock knob. Replace
the toe saver at the end of the bar. The toe saver prevents
the counterweight from falling on your foot if the lock knob
happens to come loose.
Your Sirius EQ-G mount is now fully assembled and should
resemble Figure 1 except for the hand controller, which will
be installed and explained in Section 7 (Dual-Axis) or Section
8 (GoTo).
4. attaching a telescope
The Sirius EQ-G equatorial mount is designed to hold tele-
scope tubes weighing up to approximately 25 lbs. For heavier
telescopes, the mount may not provide sufficient stability for
steady imaging. Any type of telescope can be mounted on the
Sirius EQ-G, including refractors, Newtonian reflectors, and
catadiotropics, provided a set of tube rings is available to cou-
ple the tube to the mount. Orion sells a variety of telescope
tube rings. Please visit our website at OrionTelescopes.com
for details.
1. Attach the tube mounting rings to the tube ring mounting
plate using the screws that come with the tube rings. The
screws should go through the center holes in the ends of
the mounting plate and rethread into the tube rings. Note
that the side of the mounting plate with the central “groove”
will be facing up (Figure 3). Use a small wrench to secure
the tube rings to the mounting plate.
Note: The tube ring mounting plate included with the Sirius
EQ-G includes four optical axis offset adjustment screws;
these are the socket head cap screws located at each cor-
ner of the mounting plate. These adjustment screws will be
explained further in Appendix A. For now, confirm that all four
adjustment screws are sufficiently unthreaded so that the
ends of their threaded shafts are flush with the top surface of
the tube ring mounting plate.
Note: The optical axis offset adjustment screws should be
oriented so that the threaded shaft extends upward through
the top surface of the tube ring mounting plate. If the tube
ring mounting plate arrives with the optical axis offset screws
installed backwards, reverse their orientation before proceed-
ing (Figure 3).
2. Loosen the black mounting plate lock knobs on the top of
the equatorial mount. Place the mounting plate, with the
tube rings attached, in the slot on top of the equatorial
mount. Position the mounting plate so that it is centered in
the slot. Re-tighten the mounting plate lock knobs until the
plate is secure.
3. Open the tube rings by unthreading the knurled clamps
and lay the telescope optical tube in the rings at about
the midpoint of the tube’s length. Rotate the tube so that
the focuser is at a convenient height for viewing. Close the
tube rings and retighten the clamps.
Note: Some telescope optical tubes (specifically Schmidt-
Cassegrains and Maksutov-Cassegrains) have a mounting
plate connected directly to the tube. For these telescopes,
optional tube rings are not required. Simply follow step 2
(above) to connect the telescope to the mount.
5. Balancing a telescope
To ensure smooth movement of a telescope on both axes of
the equatorial mount, it is imperative that the optical tube is
properly balanced. We will first balance the telescope with
respect to the right ascension (R.A.) axis, then the declination
(Dec.) axis.
1. Keeping one hand on the telescope optical tube, loosen
the R.A. lock lever. Make sure the Dec. lock lever is locked,
for now. The telescope should now be able to rotate freely
about the right ascension axis. Rotate it until the counter-
weight shaft is parallel to the ground (i.e., horizontal).
2. Now loosen the counterweight lock knob and slide the
weight along the shaft until it counterbalances the tele-
scope (Figure 4a). That’s the point at which the shaft
remains horizontal even when you let go with both hands
(Figure 4b). If the telescope refuses to balance then you
Figure 3. The tube ring mounting plate.
Optical axis offset
adjustment screws
Flat washer
Lock washer
Tube ring
attachment screw