Starlight Xpress SXV-AO unit - Manual (Page 8)

Handbook for the Starlight Xpress AO unit
Issue 1 21/8/2005
During extreme movement of the displacer, the motors may encounter excessive friction
and fail to start. The ‘centre’ command will normally overcome this, as it switches to a
much lower speed, high-torque stepping rate after 5 seconds of failure to move. However,
in the worst case, you can rotate the motors manually by inserting a small screwdriver
through the holes in the front plate. Be careful not to rotate them too far, as only 4 turns is
required to move the drive through its entire range. Adjust each motor until its shaft
rotates as freely as possible before using the ‘centre’ command again.
Using the AO system:
The following instructions are based on the software provided by Starlight Xpress and
will be different for other control programs. Please read the relevant help files if you are
using AstroArt or Maxim DL. I also assume that you are using the off-axis guider and
serial control of the AO.
Open the camera software and check that it recognises the presence of your main camera.
Now open the ‘Set program defaults’ menu (under ‘File’) and check that the serial control
settings are appropriate to your system. For instance, if you are using a serial port on the
PC to drive the AO unit, check the ‘AO unit available’ check box and then set the PC
COM port number. The ‘Select half rate’ box is to slow down the mount corrections that
will occur if the AO unit exceeds its useful range. You may find this useful if you have a
mount with rather erratic drives, such as an SCT on a fork mount. Now save the program
defaults and return to the main program window.
Select the main camera icon (4 from the left) and use a short exposure time to see if there
are any stars visible. Adjust the main telescope focus until you have a well focused star
field in the main camera image.
Now click on the ‘Autoguider’ icon (5 from the left) and you will see the guider window
and control panel. Select a 1 second exposure time and move the ‘Stretch image’ slider to
‘Maximum’. Press the ‘Start’ button and you should see a guide camera image appear in
the image window. At this point, there may be no stars visible, as the guider focusing
might be seriously in error. If no stars are seen, try increasing the guide exposure to 3 or
more seconds until you can detect some stars. Now use the Allen key provided to loosen
the two set screws in the guider retaining collar and then gently slide the guider
backwards and forwards until a sharp star image is seen. Note that the image might be
distorted by the telescope optics, as it is well ‘off axis’. Once focused, re-lock the collar
in place, making sure that the guide camera orientation is with the input plug parallel to
the AO backplate. Briefly blip one of the RA buttons on your telescope handset and
ensure that the stars drift parallel to the long axis of the guider window – if not, rotate the
entire AO assembly about the telescope axis until they do so. Now check that the AO
mode is set for ‘serial’ and make sure that you have selected the correct AO control port
if you are using the splitter box (ser1 or ser2). Press the ‘Use default’ to temporarily set
the guiding speed of the AO. You now have the system ready to test, so proceed as
follows: