View Single Post
  #9  
Old 23-02-2013, 10:51 PM
PTW (Patrick Wallace)
Registered User

PTW is offline
 
Join Date: Feb 2013
Location: Abingdon, Oxon UK
Posts: 5
There is a risk of confusion here between two distinct cases:
  • If your mount and control system does TPoint pointing corrections, but tracking rates are fixed, you can get spot-on slews but then unguided trailing, even if the polar axis is well aligned.
  • If your mount and control system does both pointing and tracking corrections, such as ProTrack on Paramount+TSX, then you should get both accurate slewing and minimal trailing, at least in the middle of the FoV.

Both of these apply even if the polar alignment is way off. But you will then get field rotation, and if you're guiding with a star at the edge of the field that means there will be trailing at the centre of the FoV.

Once your polar axis is within about an arcminute of the refracted pole, that's good enough unless you're planning to do very long exposures on a very wide field. And there are several choices, depending on whether you're more interested in minimizing unguided trailing or field rotation, and where in the sky you want the best results.
Reply With Quote