Byrdsfan1948 Whoever designed that could use a few good lessons in ergonomics.
Hi Al, one of the better polar scope reticules are the ones from the Takahashi EM mounts. Their scale is still too small, and back in the dark ages, I used to mount a camera at the exit pupil of the polar scope so that I have a large image on a laptop to use for adjustments (and also to avoid straining my neck with my latitude).
Unfortunately, may hobbyist products (including astrophotography) are designed by people who themselves have never practiced the hobby, or are neophytes themselves, picking up the hobby after being assigned the task of implementing the design.
Byrdsfan1948 The fine tuning adjustments needed, and the ASIair refresh delay, often lead to me chasing the target circle all over the place.
That is the biggest flaw in the ASIAIR paradigm -- their copying of Apple's easy to use GUI methodology, but without the careful consideration of said GUI.
The graphical interface of the PA process is the prime example. The problem with the ASIAIR polar alignment display is that the scale of the graphics changes! As you get closer to the target, the drawing scale suddenly changes making you think that the error has suddenly jumped higher. It is pure absurdity (as with the scale of the guide graph suddenly changing; ZWO simply does not trust the user in choosing the correct display scales). The same GUI problem are everywhere else too.
I personally ignore the polar alignment graphics completely; never even look at them. Instead, I focus on the altitude and azimuth error numbers and little green errors on the top right of the screen. Just tweak the altitude and azimuth bolts to reduce those numbers. If this numbers jump around, the problem is with the mount. The difficult alt-az adjustment caused RainbowAstro to issue a replacement base, but less scrupulous manufactures just don't seem to care about improving them. I know many people who added their own teflon sheets etc to make the azimuth adjustment of their mounts smoother.
Byrdsfan1948 I have gotten to under 20 Arc seconds but that was more luck than anything else. Last night I quit at 30 Arc Secs.
For what its worth, 30 arc seconds is well good enough for the plate scale (focal length and camera resolution) that you use.
I have been able to get within 2 arc seconds with my RST-135 within 4 minute from scratch (random tripod position), and under 2 minutes from night to night with my semi-permanent tri-pier and mount situated outdoors (I only remove the OTA and guide scope when I am done for the night).
Byrdsfan1948 Only to a few shots latter come off the rails lose that star and stop guiding again!!!
Yep, that is the guiding bug that people complained about the most, and not fixed yet. Plus they are on Chinese New Year's holidays at the moment, so who knows when a fix is forthcoming. With some mounts, don't know about yours, the bug is ASIAIR mistaking the slew rate (usually between 1x sidereal and 512x sidereal) for the guiding rate (usually between 0.1x sidereal and 1x sidereal). If you mount suffers the same bug, open up that small GOTO sub-window and drag the slew rate slider down to 1x to reduce the problem. When you calibrate, set the guide rate in the mount GUI to 0.9x. For many mounts, this (0.9x vs 1x) error is small enough to make things work sufficiently (but to us real engineers, not great).
Chen
