Author Topic: Tell me about GoTo accuracy  (Read 174 times)

asexdalo

  • Active Astronomer
  • ***
  • Posts: 118
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Tell me about GoTo accuracy
« Reply #15 on: January 11, 2018, 12:40:43 PM »
Quote
Quote

I always sync to any target I'm visiting, even if just a transitory object on the way to my real target. They don't generally come in spot-on centered, but they always come into view of my camera FOV, at which point I can re-center (and re-sync!). My camera FOV is far smaller than the eyepiece FOV.

That clarifys my head scratching wondering on why, my alignment stars are never centered when using SGP frame and focus.
When using an EP, the very first star would ALWAYS be near center. When I switched to a CMOS camera and SGP, assumed the same would happen but star is SOMETIMES not in the FOV on the SGP screen.
AFAIK, goto accuracy success is specified in observationalist terms, ie, "the target falls within the eyepiece view", which is rather large in comparison to many of the smaller chipped cameras. My camera FOV is about 1/3 as wide as that provided by a (for example) 32mm possl. So I always perform my mount alignments using the camera view, assisted when necessary by an eyepiece I swap out with the guide scope in case the first alignment star doesn't hit the mark (which is "usually"). I avoid removing the main camera to swap with an eyepiece religiously, to avoid accidentally imparted tilt during reassembly.
So once I've performed the initial alignment, resyncing on each new target avoids the drift in goto performance we sometimes see, especially when slewing far from the initial alignment stars (in my case, star, since I've never gotten a successful multi star alignment on the ZEQ25.)

I stumbled onto that "solution": back when I was using my Nexstar 130 SLT solely, which often had good initial goto performance that faded as the evening wore on.