Back on subject - Lance from Celestron replies, and what and undocumented insight / bombshell he drops. Although the mount perfectly models the sky and understands after alignment your pointing error, it only correct for this during Goto - not tracking!
What a 24 carat whoopsie! I don't see why this isn't programmed in, it surely wouldn't be that difficult! Failing this why not document that critical feature Celestron? I had pondered that drift alignment was a nice but unnecessary task on a clever Goto GE mount - boy was I wrong!
Also Lance still hasn't told me how can I go to Sigma Octans? It doesn't appear in the Named Stars section of the menu - is it a SAO or IC item, or is it normally un- goto - able?
Lance's kind reply to my three questions in my first post!
- I believe that you do not quite understand how this polar alignment routine works. The mount simply moves to an object that is close to the Celestial pole. For northern hemisphere observers, it goes to Polaris which is actually 0.8 degrees off of the NCP. For observers in the southern hemisphere, the mount chooses Sigma Octanis, which is unfortunately, the closest star to the SCP. The mount points to where Sigma Octanis should be with respect to the mount’s starting position at that exact date and time. The scope does not show you the amount of “offset”. You have to mechanically adjust the scope using the altitude and azimuth screws to bring Sigma Ocatnis to the center of the field of view. A star closer to the celestial equator will not work well for polar alignment as this introduces cone/hub errors into the equation. You need to use a star that is as close to the celestial pole as possible.
- This is similar to a compass coordinate. 0 degrees is at north. 90 degrees is east. 180 (or -180) degrees is south. 270 (or -90) degrees is west.
- Any time you manually adjust the mount after a computer alignment, the computer’s alignment is no longer valid. You will need to realign on three stars. Once aligned the telescope will compensate for poor polar alignment and will successfully point to any object, but may not track properly. Being a German equatorial mount, only the R.A. motor is operating during tracking. If you have a poor polar alignment, the scope will be able to hit the target, but will show declination drift when tracking. An accurate polar alignment is a necessity if you want excellent tracking.