Polar Alignment.

denababy

Here Iam again, whilst using aap to Polar align, when it slews 60’ it goes to the left which means it points at my house but if it slewed to the right it would not point to the house so is there a way of getting the mount to slew the opposite way?

w7ay

denababy Here Iam again, whilst using aap to Polar align, when it slews 60’ it goes to the left which means it points at my house but if it slewed to the right it would not point to the house so is there a way of getting the mount to slew the opposite way?

If "aap" refers to the ASIAIR, start with the Mount tilted to the right (when viewed from behind the mount), instead of straight up.

ASIAIR does not care where you start and where you end, as long as it has two clear views at the beginning and at the end of the slew. Any two angles that are separated by about 60º.

See post number 2 of this thread:

https://bbs.astronomy-imaging-camera.com/d/12532-cannot-polar-align

And it is 60 degrees not minutes of arc. A 1 degree slew would yield a highly inaccurate pole location.

Chen

denababy

Thanks Chen, I have an AVX mount and started with the marks in the basic position then I moved the mount 60 degrees to the right, using my inclinometer, and marked that position. From this new position do I need to ensure the Pole star is in view before I start the PA?

w7ay

denababy From this new position do I need to ensure the Pole star is in view before I start the PA?

I don't understand the question. As outlined in the two links that I gave, the pole need not be visible with ASIAIR's polar alignment. Polaris need not be visible either (Polaris, which is not located at the pole, is of no importance at all unless you are aligning with the legacy polar scopes).

Polar Alignment is the process of getting the mechanical axis of the mount to point to the NCP (or SCP). It just needs to know mathematically where the pole is located; it does not need visibility of the pole (again, look at the diagram on the two threads that I linked to).

ASIAIR uses plate solving to locate where the mount is really pointing at the beginning, and at the end points of that 60 degree traversal.

If you are manually moving the mount the way you outlined, be sure that after polar alignment: remove the mount from ASIAIR Telescope Setup, reset power on your mount after moving it back to its home location, do a star alignment, and then reconnect to the Telescope setup on ASIAIR again.

It is best that you do not loosen any clutches. In the case of a SynScan based mount like yours, declutch and set to home with power off, then tighten the clutches and never touch them again, and then power the mount on. (This tells the mount its approximate home position since there is no absolute encoder on your mount -- you need a more expensive mount for that.) From this point on, never declutch again. Star align your mount. (This step relates your mount's motors to the RA and declination of the sky.) Only then do you connect the mount to ASIAIR's Telescope Setup window. These two steps (and correct time information is needed or you will be driving the mount into the ground the next time you do a GOTO (and a Meridian Flip will also fail at the proper time). With a better mount, you just have to turn it on, and you are off to the races.

To slew the mount to any angle (for example the 60 degrees pre-tilt), use the directional arrow keys in ASIAIR. Again, do not declutch to do that step. Use the RA keys to tilt the host angle, and the declination keys to move the OTA from the pole in case it is also needed.

Chen

denababy

Thanks for that, hopefully when I try it everything should be ok.