Orion 52080 - Manual (Page 17)

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Some telescope mounts, such as the Orion Atlas EQ-G and Sirius EQ-G, uti-
lize an “ST-4 compatible” autoguider jack. For easiest autoguiding with these
mounts, we recommend purchasing the optional USB Guide Port interface
(GPUSB). This adapter box will translate the autoguiding computer commands
from MaxIm DL Essentials into ST-4 pulse commands. The GPUSB connects
to the computer’s USB port instead of the COM port. A cable then connects
the GPUSB to the mount. In addition to installing the ASCOM platform on your
computer (from the Install ASCOM button in the Launcher), you will need
to install the GPUSB ASCOM driver (downloadable from the Orion website,
www.OrionTelescopes.com). Then, you can select the GPUSB in the ASCOM
Telescope Chooser.
Other telescope mounts accept commands in the “LX200 Protocol”. For these
mounts, it is not necessary to install the ASCOM platform to have the com-
puter “talk” to the mount. To setup the autoguider for mounts that use the
LX200 Protocol:
1. Connect the SSDSI-II to your computer and open the Maxim DL Essentials
software.
2. In the Camera Control Window, click on the Guide tab.
3. Click on the Settings button.
4. In the window that pops-up, select LX200 Protocol for the Autoguider
Output Control Via. Select the COM Port of the computer you would like
to use to send commands to the telescope
5. Click the Apply button, then click the Close button.
Autoguider Calibration
In order to properly control the mount, you must calibrate the system. The
exact orientation of the SSDSI-II, the focal length of the guide telescope
optics, and the speed of the motor drive all affect the calibration. To perform
autoguider calibration:
1. Switch to the Guide tab.
2. Set the X and Y Aggr (aggressiveness) to 8 to start with. Set the Exposure
to 1.0 second. Under Guide Star, make sure the Watch box is checked.
Note: The X and Y Aggr (aggressiveness) controls on the Guide tab allows
you to adjust how vigorously star motions are tracked out in each axis. An
aggressiveness setting of 10 means that the SSDSI-II attempts to track out
100% of the motion, whereas a setting of 1 means that the SSDSI-II only tracks
out 10% of the motion. Usually a setting of around 8 or 9 provides the best
tracking, since it reduces overshoot and helps ignore random motions due to
atmospheric seeing and wind loads. You should experiment to determine the
best setting for your particular telescope.
3. Click the Settings button.
4. Maxim DL Essentials needs to know how fast the telescope moves in right
ascension (R.A.) and declination (Dec.) when the autoguider commands
are issued. To do this, the software will Calibrate the mount by moving it
back and forth on each axis. The Calibration Time determines how long it
activates the motors each time. The usual value is 5-10 seconds; start out
with a value of 5.
5. Make sure all of the Guider Enables boxes are checked.
6. For Autoguider Output, set Control Via and COM Port as required for your
telescope equipment. See “Computer to Mount Connection” if you have
not already done this.
7. Click Apply. You can leave this dialog box open, or Close it if you wish.
8. Make sure that the telescope mount is set to move at 1X sidereal or slower.
For some mounts, you must set the guide rate manually. The maximum
usable rate is 1X sidereal. If your mount does not drift quickly, then 0.1X is
recommended; otherwise use a value between 1X and 0.1X.
9. On the Guide tab, set to Expose, and click the Start button. A single image
will be taken. Ensure that a well-focused bright star (near the actual object
to be imaged) appears in the image. If not, adjust the guide scope and try
again. Make sure the star is roughly centered.
Note: The algorithm can be confused if another star appears in the frame; to
minimize this risk, calibrate on an isolated bright star.
10. Now, set to Calibrate, and click the Start button. A series of five exposures
will be taken; each time the telescope will be moved slightly. If the tele-
scope does not move, check the Settings. Remember, you have to set up
a method for sending the autoguider commands to the telescope!
11. The star should move in an L shape. If it does not move enough, a warning
message will appear. The recorded positions will be displayed in the scroll-
ing log, along with any error messages.
Note: If the star does not move far enough, or moves too far (i.e. the star leaves
the field), the duration of the calibration move commands can be adjusted
by clicking the
Settings command and changing the Calibration Time fields
(measured in seconds). A longer calibration time will increase the motion of the
star; a shorter time will decrease the motion. Typical values range from five to
ten seconds, depending on the correction speed, focal length, and pixel size.
12. Once you have successfully calibrated, switch to the Track mode. Click
Start, and watch the star. It should move to the center of the small track
box, and whenever it drifts off it should be pulled back again. You can
zoom in the window for a better look. Also the tracking errors will be dis-
played in the scrolling log.
13. If the star bounces back and forth, reduce the aggressiveness for that
axis. If it corrects too slowly, increase the aggressiveness. Changes to the
aggressiveness settings take effect immediately.