PART 1: Introduction
Welcome to the official tutorial on using PHD2 and the bookmark technique to dial in extremely precise polar alignments. Many of
you may already be aware of the fact that PHD2 can be used to perform polar alignment. What you may not be aware of is that polar
alignment with PHD2 can be extremely accurate, and that it can be done without necessarily having line of sight on polaris. For
those of you who have an obstructed view, or live near the equator, aligning with PHD2 is a free, easy way to achieve very
accurate polar alignment very quickly.
I am also sure some of you have tried PHD2 drift alignment, and given up on it. You found it clunky, difficult to avoid cycling
back and forth between one bad alignment and another, etc. You may have even put money into another tool to solve your alignment
problems, tools that may rely on the (potentially inaccurate or imprecise) pointing accuracy of your mount for "iterative"
alignment. This tutorial aims to introduce you to the key feature of PHD2 that alleviates these problems, making polar alignment
easy, fast, and consistently effective...at dialing in VERY accurate PA: bookmarks.
If your like me, you've noticed the bookmark feature of PHD2 throughout your time using it, but never realized with a use for
them. While trying to improve my PA a few weeks ago, early August 2014, I was struggling with PHD2 drift alignment while trying
to move the guide star the right amount, relative to it's previous position. It hit me at that point that bookmarks would be a
perfect way of guaging how far, and in what direction, I needed to move the guide star, in order to properly refine my alignment.
The key benefit of polar aligning with PHD2 is it requires only the adjustment of your altitude and azimuth adjustment knobs or
bolts. This is a benefit, in that it means you can dial in an accurate polar alignment without having to rely on the pointing
accuracy of your mount (which may be limited to 1-2'). This alignment technique does not require iteration between two stars, and
therefor does not require you to move the mount at all. At least, not beyond the initial pointing towards your alignment star
(near the meridian and CE for azimuth, or horizon and CE for altitude). Once pointed, all adjustment is done purely with the
alt/az adjustments on the mount.
All of the frustrations with PHD2 drift alignment can be eliminated by using bookmarks. By marking the current position of the
star before each adjustment with alt/az knobs, you have a clear guage of where the star was, and after a couple adjustments, you
know exactly what effect turning your adjustment knobs one way or the other has on the star position relative to where it was.
This takes a lot of the guesswork out of PHD2 drift alignment, which is probably the greatest source of frustration, and a key
reason why it can be just as timeconsuming as other methods. Bookmarks also help you define a shrinking range as you add more
bookmarks, guaranteeing that, somewhere between two of those bookmarks lies a perfect polar alignment.
With just a few iterations of drifting, placing bookmarks, and making smaller and smaller adjustments, you can dial in a polar
alignment less than 0.5' (<30") off the NCP, and if your persistent, within a few more iterations you could dial in a polar
alignment less than 0.1' (<6"). With a little bit of practice, performing fast, highly accurate polar alignment to ten arcseconds
off the NCP can be achieved in *less than 15 minutes.* This screenshot shows the kind of tracking and guiding performance that
is possible with a very accurate polar alignment:
Edited by nitegeezer, 21 August 2014 - 11:13 PM.
Edited at request of Jon