On Sat, Aug 7, 2021 at 10:22 PM, Michael Herman wrote:
Peter says he is getting outstanding PHD2 tracking, like 0.6 arcsec, from his piggyback guide scope and it's autoguide camera.? But he is perplexed by getting oblong stars in his main camera when he is pointing South like to Sagittarius.? When he points to zenith he gets excellent tracking and excellent images.
Michael,
Since Peter is in the UK (I think), Sagittarius must be pretty low in attitude (20 degrees?), even as it crosses the meridian. That's a lot of air to see through, so could this be more atmosphere than weight shift? When I start seeing stars that are oblong, usually the PHD2 errors for RA and Dec are no longer are close in magnitude, and that's when I might start playing with the Aggression and MinMo settings, or increase exposure seconds.? Just wondering what the RA and Dec errors might look at a few places higher up, like 40 or 60 degrees altitude, and which axis is more greatly affected. Usually I don't do any deep sky AP below 30 degrees as the slop is just too much. 0.6 or less is pretty for common for me at zenith, though I might see about 0.45 or a bit less on nights with very good seeing, looking up through only one atmosphere.
Best Regards,
John
