Polar Alignment (again)

Hi Jared/Ken,

Just for conversational sake (since many of us here are technical), can you share any details on the Polar Alignment integration? Did the plate solving / math prove unreliable?

This isn’t a feature request. Between the AP RAPAS and PHD2’s Drift Align tool, I’m fine with PA and may be faster as is, too. However, it would be a cool add-in, though agree with previous comments in old threads about focus, other core functionality being a higher priority. Just wondering.


The math is fine… just never got around to nailing down the procedural aspects of the routine.

PHD2 has a fantastic drift alignment tool. Have you tried it?

Yep – as I said in my original post :slight_smile: It is a great tool. I start with the RAPAS and might tweak using PHD2’s drift align depending on what I’m after / exposure time.

The great thing about using it is that it can be done just after sundown, so it’s plenty of time to get polar aligned. PHD2 as a whole has been rock solid and amazing. (As is SGP.)


Fun fact I learned about the PHD2 drift alignment tool. Make sure you calibrate it at the declination for drift alignment… Apparently it will introduce errors in the measurements otherwise.


Hi Chris,

I really don’t think that is true, but maybe I am missing something. Could you elaborate on what led you to that conclusion?


Now I can’t find it :slight_smile: I thought I’d read it on your forums.

Maybe it had something to do with the dual recommendations to calibrate and to drift at low declination (near the celestial equator).

  • Calibration is best done at low declination where the RA and Dec guide rates are nearly equal and the RA motion of the guide star is greatest for a given RA guide pulse.
  • Drift alignment is best when done at low declination, since RA drift due to polar alignment error is close to zero at declination zero.


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I think that is what I read. So, my take on it was to do a calibration before I started drift aligning.