Kevin_A I never have to change direction when getting close to perfect PA.
That is a very sage advice.
With my RST-135, if I overshoot the altitude, I would back off a lot and start all over again in a single direction. The backlash would otherwise drive me completely crazy.
I always start off with my mount pointing slightly lower than polaris
That does depend on the mount though, and in the case of strain wave gear mounts that are completely imbalanced, it depends on whether the imbalance is heavy towards the objective end of the OTA, or towards the instrumentation end.
Whatever the balance is, you want the altitude bolt to be working against gravity.
With my Takahashi EM-11, which requires a good balance to start with, I would temporarily lash a bungee cord to apply an extra force to keep the altitude adjustment biased to one end, until I finally lock it :-).
I have actually given up on adjusting the altitude of my cheap mounts (EM-11, and a couple of RST-135). Since I have a quasi-permanent setup outdoors with a William Optics Mortar sitting on concrete stepping stones that I do not move, I have oriented the tri-pier so that two of the legs point ESE and WSW, and the third leg pointing to true north.
I then use the North leg leveler of the Mortar as my final altitude adjustment. Works peachy, and since the moment arm of the tri-pier leg is so long, I could get arc-second type resolution with the leg leveler without breaking a sweat. That north leg has to point moderately well to north, otherwise an adjustment there will also affect the azimuth pointing. Cannot be pointing Northeast, for example.
This is also why you want to level the base of your mount to less than a degree, otherwise there will be a mutual coupling between the altitude and the azimuth adjustments (the off diagonal elements of the tranformation matrix between alt-azimuth coordinate system and the spherical coordinate system are not zero).
Very often, some Facebook or YouTube smart alec would come along to say you don't need to level your mount to polar align, without knowing the underlying geometry involved. Same person probably is forever going back and forth between the two knobs. If everything is leveled, a good mount that has no orthogonal problem will not change altitude adjustment after tweeking the azimuth knob and vice versa.
Chen
