PWI Telescope Control Software Manual

16
• Backlash - This selection allows you to set the backlash compensation for each of the mount’s axes of motion. Mechanical
gears have a certain amount of backlash or play between the gears. This play is evident in the amount of time it takes for a star
to move in the eyepiece when reversing slew directions. The amount of gear backlash is constant, so with the slower slewing
rates, it will take longer for the star to move in the eyepiece when reversing directions. CPWI’s anti-backlash feature allows
you to compensate for backlash by inputting a value that quickly rewinds the motors just enough to eliminate the play between
gears. The amount of gear backlash is different in each mount, so you will need to experiment to determine the best value for
your mount. Most mounts work best with values between 30 and 70. It is generally better to have a value that is too small than
too large. If the value is too large, you will see the object overshoot when you change directions, which will make it hard to
center objects in the fi eld of view.
NOTE: Gear backlash compensation is only recommended for visual use and may be counterproductive when used during
astrophotography. When tracking is enabled, the mount will be moving in one or both axes. Pressing a direction button
opposite to the direction of tracking will cause the gear backlash compensation to activate twice; once when you push the
direction button, and again when you release it and tracking resumes.)
To set the anti-backlash value, enter a value from 0-99 for both RA and Dec (or AZ and ALT). CPWI will remember these
values and use them each time you turn the telescope on until the values are changed. If you do not want to use any backlash
compensation, make sure the value for each axis is 0.
• RA Slewlimits (EQ mounts only) – This selection allows you to set how far beyond, or how far before, the meridian the
mount will slew in RA before requiring a meridian fl ip. This functionality is especially useful during astroimaging, as you
may want to track an object through the meridian for as long as your mount allows before performing a fl ip. To use the RA
Slewlimits, fi rst select the “Enable” checkbox, then set the limits for East of the meridian and West of the meridian. Negative
numbers indicate the number of degrees past the meridian. The limit is -20° since most Celestron EQ mounts cannot slew
further than 20° past the meridian due to mechanical limitations. A positive number indicates a meridian fl ip will occur before
the mount reaches the meridian. +40° before the meridian is the maximum value allowed. (NOTE: It is important to know the
mechanical limits to motion past the meridian for your mount before these limits are entered, otherwise you may reach the
mechanical limit before the software slew limit, which may cause you to need to realign the mount.) (NOTE: AZ mounts on EQ
wedges do not have a limitation on how far past the meridian they can slew.)
• Altitude Slewlimits (AZ mounts only) – This selection allows you to the defi ne the allowable slew range in the altitude
axis. This can be useful for preventing accessories attached to the rear cell of the mount from hitting the base of the mount
when the telescope is pointing straight up. To use the altitude slewlimits, fi rst check the “Enable” box. Then, set the lower
limit and upper limit to the altitude slew range (0° is the horizon, 90° is zenith).
• AutoGuider Rates – This selection allows you to set the autoguiding rate as a percentage of sidereal rate. This is helpful
when calibrating your telescope to an autoguiding camera for long exposure astroimaging.
• Tracking – Choose from sidereal, solar, or lunar rates. The current tracking rate selected will appear in the “Mount State”
section of the Data bar at the top of the screen. For EQ mounts, you can also activate tracking in both axes by selecting the
“Ra + Dec Tracking” checkbox. This can be useful to use if your polar alignment isn’t very good.
• PEC – Enables PEC playback for mounts that support it. (See Train PEC below.)
• Meridian Sweep (EQ mounts only) - This function instructs the mount how to respond to GoTo commands when slewing
to objects that are near the meridian. It can be used to prevent unwanted meridian fl ips. Meridian Sweep allows the telescope
tube to remain on a desired side of the mount after slewing to the object. (NOTE: If the RA Slewlimits are enabled, they will
provide a limit to how far past the meridian the mount can go until a meridian fl ip is performed.) (NOTE: AZ mounts on an
equatorial wedge do not require this function, as they do not need to perform a meridian fl ip.)
Once enabled by selecting the “Enable” checkbox, there are three options:
• Favor East – If the target object is accessible from both sides of the mount, selecting “Favor East” instructs the mount to
GoTo to the object as if it were on the east side of the meridian. The optical tube will then be positioned on
the west side of the mount and pointing east.
• Favor West – If the target object is accessible from both sides of the mount, selecting “Favor West” instructs the mount
to GoTo to the object as if it were on the west side of the meridian. The optical tube will then be positioned
on the east side of the mount and pointing west.
• Favor Current – Selecting “Favor Current” instructs the mount to favor whichever side the mount is currently on when
slewing to objects close to the meridian.
The “Angle” selection box allows you to choose how far past the meridian the mount can slew during a GoTo command before
the meridian fl ip is performed. Make sure the number you enter in this box is less than any negative slew limit if RA Slewlimits
are enabled. If RA Slewlimits are not enabled, then make sure the “Angle” is less than the number of degrees that your mount
can move past the meridian before mechanical interferences occur.
• GoTo Approach Direction – Use this setting to change the direction of the mount’s fi nal approach when slewing to an
object. You can change the approach direction for each axis of the mount. For EQ mounts, RA positive means the mount