ben_eisenstein It seems that many of us users do not have a view of Polaris.
The statement that ASIAIR requires Polaris to run its Polar Alignment tool is totally false. I don't know who started spreading the falsehood, but it got repeated often that most people think that you need to see Polaris.
ASIAIR does not need to see Polaris, or more appropriately the North Celestial Pole (NCP), since Polaris is not located at the pole. In the southern hemisphere, you also do not need a view of the South Celestial Pole.
To estimate the center of rotation of the RA axis, all ASIAIR needs are two clear fields of view of the sky, about 60 degrees apart in Right Ascension (RA), and less than 30º in declination from the pole. That center of rotation (the location of the NCP when you have finished polar aligning) does not have to be present in the sensor plate. It is just a virtual coordinate.
(Note that when ASIAIR performs a 60º rotation, the declination axis is held perfectly constant -- only the RA axis of the mount slews.)
See this thread in the ASIAIR discussions. I have drawn and posted a diagram that shows the type of situations that will work (NCP below a roofline or horizon), but there are plenty of other possible configurations too (e.g., a tree branch obstructing the NCP itself, the roofline is diagonal, etc).
https://bbs.astronomy-imaging-camera.com/d/11580-polar-alignment-without-polaris
Scroll down to Post #11 of the above thread for the diagram.
The closer these two views are to the pole, the more accurate the polar alignment is. From my latitude of about 45º North, if I am within 0.5º of the pole, I get an accuracy of better than 5-12 arc seconds, depending on the "seeing." With the declination of the two views 15º away from the pole (not minutes or seconds but degrees; Kochab's declination is about 15º from the pole and you can look up at the night sky to see how far that is), the accuracy is still well within an arc minute, which is more than sufficient to not notice any field rotation with 300 second type exposures and 1000mm type focal lengths.
With the declination of the two views at 30º from the pole (the limits of the polar alignment plate solve), the polar error is still a respectable 2 arc minutes, if memory serves. That is more than good enough to render field rotation unnoticeable for 180 second exposures and 500mm type focal lengths.
Chen
