|
I recently had the same issues guiding with a SX lodestar at 1800mm. I found that some tweaking was needed in PHD.
I was guiding at 1s intervals. The first thing I had to do was increase the minimum distance from 0.15px to let's say 0.25px before a correction was issued. I also had to explicitly set DEC guiding North or South depending to avoid switching direction. Finally had to pay particular attention to balance and drop the maximum pulse time to 30ms in DEC and 180ms in RA. I also had to lower the calibration steps down to 400ms. That gave me approx. 10 to 12 steps on each axis and back.
At the end of the day if your mount is giving you +/- 2" peak to peak and your image scale drops under 1" it will be very hard to stay within the same pixel on the imager. All you can do is smoothe the rate of corrections. One good night out of 4 I went down to 2.1" FWHM and my guiding was within +/- 1". Other nights it would be 3-4" FWHM and I couldn't keep the guiding within +/-2" with the same settings in the exact same region of the sky which was right ahead at the zenith.
|