I have a question about alignment  I can't understand how it works if more than one stars for alignment.
So if my altazimuth mount does  not set horizontally well enough, will it calculate and rotate all its coordinate system accordingly?
My Nextar 8 mount does it very well.

I think we need 3 point to conver one coordinate system to another one. Polar star and another two with well known coordinates.
I hope you understand what I mean. I can't make so accurate explanation in English.
Thank you.

So, no one knows how onstep calculate its position? 

I don't have a specific answer for your question, which is vague. Are you asking specifically
about when the mount is not leveled correctly?

But here is some info:

The first star alignment just brings the celestial sphere and the internal coordinates
together.

Internally, OnStep calculates the following errors:

  ax1Cor=0;  // align internal index for Axis1
  ax2Cor=0;  // align internal index for Axis2
  altCor=0;  // for geometric coordinate correction/align, - is below the pole, + above
  azmCor=0;  // - is right of the pole, + is left
  doCor =0;  // declination/optics orthogonal correction
  pdCor =0;  // declination/polar orthogonal correction
  dfCor =0;  // fork or declination axis flex
  tfCor =0;  // tube flex

The altCor and azmCor are the errors in Altitude and Azimuth (mount not perfectly
aligned with celestial pole). To calculate these, you need at least a 3 star align. So,
this is the minimum number you should use for accurate gotos.

The more stars you align on, the better the alignment. All boards offer a 6 star align,
and you can increase that in the Config file (at the expense of a couple of minutes
of slowness while the calculations are being done).