On the night of Aug 02/03, 2022, under very pleasant conditions, I ran some tests for using an autoguider at the focus on a small telescope mounted piggyback on the 14-inch Celestron in the roll-off structure. After a week or so of failures and frustration, the system finally worked. Hooray!
Here's the setup:
When the telescope is on the East side of the pier (pointing to targets West of the meridian), this yields a display in PhD2 with North up, East to the left. If the telescope moves to the West side of the pier (pointing to targets East of the meridian), the field is rotated by 180 degrees.
With this 0.5x focal reducer, the plate scale of the guider is 2.15 arcsec/pixel, and the field of view is roughly 35 arcminutes on a side. The PhD2 program provided a nice summary of the camera properties based on its calibration:
When setting up the profile of this combination in PhD2, I did the following:
I then named this profile relay_ssag_aug02_2022, for future reference. You can see these settings in the "Connect Equipment" menu of PhD2.
It's a good idea to create a new dark library at the start of the night. I did so, and then a second one later on after the temperature had dropped quite a bit.
One important note is that the PhD2 calibration procedure did not seem to be working properly at first. I eventually discovered that one of the issues was the size of the guide pulses; the default is 200 ms, but that produced _very_ small motions in the calibration procedure. When I increased the pulse duration to 900 ms, the calibration finished successfully.
I also discovered that the cable I had been using to connect the guide camera to the "Autoguider" port on the mount was not working. It may not have had the proper connectors: one must use RJ12 connectors at each end, not the ordinary RJ11 phone jack connectors. Fortunately, a proper cable was packaged with the Orion StarShoot camera. However, although it served the purpose for this test, I'll need a longer one; I should order one soon.
An example image can be seen in the screenshot below, which shows at 3-second snapshot of the field around M57. In this image, North is down and East to the right, due to the flipping of the telescope when I moved from looking at the western sky to the eastern. Stars of magnitude V=10 and V=11 can be seen easily. The star used for guiding is APASS 14384856 with V=8.712 and (B-V)=0.007.
I ran a guide session on this star, using 3-second exposures. After a run of 17 minutes, PhD2 reported that the RMS was 0.41 arcsec in RA and 0.46 arcsec in Dec. That would be just fine!
There are still plenty of tests to run, and lots of tuning, but I think that this system should suffice for all our needs. Thanks very much to Brian Valente and Bruce of the open-phd-guiding Google group.