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Astro-Physics Command Center (APCC)
includes tracking and pointing correction based on calculations from
atmospheric refraction all the way up to sophisticated real-world models based on plate-solve data for your specific
instrument package.
I'm trying to track down what I believe is a small backlash in Dec At some elevations, stars show tiny
trails (not full brightness) on the Dec axis, and I attribute those to backlash.
Firstly, the Mach2GTO will not exhibit mechanical backlash due to the action of the absolute encoders. Secondly, backlash
by itself does not produce trails.
Backlash is a term used to describe clearance between the teeth of a pair of gears. The correct term for Dec is actually
delay in reversing the axis (Reversal Delay), which is highly dependent on what guide speed settings you are using. At
1x guide speed it might take 0.5 seconds to fully reverse the Dec axis motion. At .25x guide speed it will take 2 seconds,
which would cause considerable delay if you are dithering. Under normal guiding, neither of these would impact the guide
software to properly guide the mount.
If you are guiding, the guider software automatically handles any Dec backlash. If unguided, backlash has no effect at
all. For guiding purposes, the best thing is to leave Dec backlash compensation at zero otherwise you risk overshoot and
constant oscillation back and forth on the Dec axis.
The mount will not go to the park 3 position.
Normally a mount will never do what you are describing, even if you have a power loss during a slew. However, this
situation can occur if, during a session, you did a ReCal on a wrong position. It can occur if you did a time change during
your session, or changed the daylight savings time. For each hour of time change or daylight savings the parks will move
15 degrees.
The mount is not tracking at the correct sidereal rate.
The sidereal rate is very precisely determined with a quartz crystal in the GTOCP5. If you really want to check your RA
driving rate you can set the rate to Stop, place a piece of tape across the stationary and moving part of the RA axis. Cut
the tape at the seam between the axis. Get an accurate timer, set it to the sidereal day (23hrs,56min, 4.09sec). Push the
timer and set the rate to Sidereal at the same instance and let the axis track until the next day. Check when the tape lines
up exactly with the timer. Or you can set it to Solar rate and set the timer to 24 hrs. We have done this a number of times
with mounts that people swear are running fast or slow and every time the results are within a small fraction of a second.
For a more detailed, illustrated explanation of this procedure, please refer to
I am experiencing RA drift.
There are numerous potential causes for RA drift. Please refer to
I think my CP5 Ethernet port is broken.
Plug in the Ethernet cable to the computer and CP5, then power on the CP5. Look at the Ethernet port on the CP5 when
you do this to verify that the amber LED is on continuously and the green LED is flashing sporadically for a while before
stopping. If the amber light is off, there is no physical link being made to the computer, and the cable is likely at fault. If the
amber light is on but there is no green flashing, then the computer and CP5 are not handshaking.
APCC (or any other program) can’t find the CP5 over Ethernet.
Check to see if you can open the home page in a browser. If you can, the computer and CP5 are connected properly
and the issue is with the software. Consult the manual for the software to see if they have more specific instructions. If
you can’t open the home page, you might have an IP overlap. This can be solved by changing the CP5 IP address. For
example, changing from 169.254.3.101 to 169.254.3.102 might solve the issue.
The Wi-Fi signal is inconsistent and my mobile device is not communicating.
Some users have reported issues with the Wi-Fi randomly dropping or having trouble even when right next to the CP5.
This may happen if the CP5 Wi-Fi signal is too strong at that distance, and is causing temporary deafness in the receiver
of your device. Steps to take include keeping the CP5 antenna folded down and standing further away. In extreme cases
aluminum foil may be used to shield the external antenna. You may also try disconnecting the external antenna.
Alternatively, you may need to move the antenna or even your GTOCP5 to another position for a clear line of sight to your
modem. The heavy metal mass of your pier could interfere with the signal. Be sure that your antenna is free of other
