To perform a calibration, perform the following steps:
1) Center a guide star in the image window and define a very large region mask
around the guide star. The large mask is necessary since the program will be
telling the telescope to slew a potentially large distance.
2) Define the
‘
calibrate backlash pixels
’
and
‘
seconds
’
fields. Your mount will
have some backlash in its drive train and this is how we compensate for that.
The
‘
pixels
’
field defines the distance the guide star position must change be-
fore the program decides it has taken up all of the backlash in the system.
The
‘
seconds
’
parameter tells the program how long to slew the scope before
deciding that the backlash is taken up. Both of these conditions must be met
for the program to decide that the backlash is taken up.
3) Define the
‘
calibrate movement pixels
’
and
‘
seconds
’
parameters. This tells
the program how long to slew in a particular direction while characterizing the
mount
’
s movements. So for example, a longer slew time will be needed for
telescope mounts that will be guiding at a very slow rate. Fast guide rates will
need a shorter time to be entered.
4) Setup the telescope
’
s mount controller for the desired slew speed you will be
using to guide.
5) Press the
‘
Calibrate
’
button. The program will begin to slew the telescope in
both the NORTH and then WEST directions in order to determine how the
mount moves relative to the commands being given it. The result is to fill in
the
‘
NORTH Slew Counts/sec
’
and
‘
WEST Slew Counts/sec
’
number fields. At
the end of the calibration sequence, these fields will display the displacement
in guide star position (pixels) for a one second slew command. A bigger num-
ber will represent a mount with a faster slew speed or a long optical focal
length lens in front of the camera. A negative number signifies a reversal in
direction.
fishcamp engineering
Starfish
Guide Camera
