Pedzsan I think what I need to do is PA and when that is done, move the mount via the arrow buttons provided for when in Preview Mode, then take a Preview image (very important!!!), then hit Solve, then Sync to Mount… then the Goto will work correctly. Is that right?
Nope.
Polar Alignment is the process of getting an Equatorial Mount's RA axis perfectly parallel to the earth's rotation axis. This way, you can track a star's daily movement by moving only the RA axis, and at a constant rate, and polar alignbment also reduces the field rotation to something small enough.
There are many ways to do polar alignment. The most precisly way is arguably by using the "drift method" (see https://www.explorescientific.com/pages/polar-alignment-using-the-drift-method). If you have a permanent obsevatory, it is probably what you would use. BTW, the von Fraunhofer that is mentioned in the Explore Scientific artical is the reason why the style of some equatorial mounts is called "German Mount." (https://en.wikipedia.org/wiki/Joseph_von_Fraunhofer)
Do a google search for "Frank Barrett & polar aligment," to see the equations that are involved in polar alignment.
ASIAIR uses two points in the sky that have the same declination in your mount's coordinate system. It gets the two locations by using plate solving. After polar alignment succeeds, the mount's coordinate system will be identical to the sky's coordinate system.
Plate Solving is the process of finding the center of a photographic plate (nowadays, sensor image) by using star asterisms. Go browse astrometry.net to learn how it works.
Plate Solving within 10º of the pole is pretty routine. ASIAIR is simply too naive a program to accomplish it. You can use a different computer program, or send your image to nova.astrometry.net, to plate solve successfully even when you are pointed at the pole.
To perform a polar alignment, ASIAIR take an initial location, then moves about 60º by only moving the mount's RA axis. The declination is kept constant -- otherwise, you would need one extra measurement to determine how far your yount's RA axis is away from the pole.
When you ask ASIAIR to refresh the polar alignment error (how far away your RA axis is pointed to relative to the pole), it takes another image, and finds the new center of the frame by doing a fresh plate solve.
After a polar alignment, ASIAIR has a bug if your mount crosses the Prime Meridian during that 60º slew. After a Polar Aligment, the pier side of ASIAIR and the pier side of the mount can differ, causing a GOTO command to send the mount to its equivalent meridian flip position instead. You can get around ASIAIR's bug (it has been around since ASIAIR implemented polar alignment) by asking the mount to perform a home fiunction. After a home, the mount's pier side and ASIAIR's pier side are in sync again.
Go to Amazon, and do a search for "astrophotography" books. Do not watch the YouTube shills; except for a number of YouTuve videos that you can count on the fingers of one hand, they teach you nothing about astrophotography except for the product they are trying to push -- read a book instead.
Chen
