Editing Polar Alignment (section)

=== Drift alignment ===
----To understand drift alignment it's important to understand what we're doing, why we're doing it and what we're trying to achieve. Drift alignment seems to be the form which most often confuses an puts off beginners into the hobby. It's actually fairly simple once you understand it.

The fundamental basic of polar alignment is that we're trying to align the R/A (Right Ascension) axis of the telescope with the axis that the earth spins upon. We can adjust the R/A axis in two ways - from side to side (the azimuth adjustment) and up and down (the altitude adjustment). This is kind of similar to how a dobsonian telescope works - the alt and az bolts are two pivot points with which you point your R/A axis similar to how a dobsonian uses two pivot points to point a telescope.

This is shown on the diagram below - the R/A axis is marked in red, the azimuth pivot point is marked in pink, and the altitude pivot point is marked in blue. On most mounts there are screws to adjust these.

In drift alignment we start with the azimuth adjustment.

==== Azimuth adjustment ====
In the azimuth adustment we are trying to get the side-side alignment of our R/A axis right. Set up your mount as normal, use the polarscope or a compass to get it pointing fairly close to North. Turn on your telescope and get to a point where it is tracking the stars. You don't need to do any star alignments for GOTO functions at this point.

Next, use the handset to point the telescope at a star which appears to be near the meridian, south of your telescope. Watch the star through an eyepiece or BackyardEOS's live-view (it has a really handy drift align reticle for this purpose where you can zoom in). Watch for motion in the star. Assuming you're not super lucky and haven't managed to point the mount due north to start with there should be some movement (drifting) visible in the star. The motion of the star tells us how well our mount is aligned.

If the R/A is too far '''East''' the star will appear to move '''North''' in the field of view.

Look at the path of the star (black arc) in relation to the path of our field of view (thick red arc) in the image below. The path of the star goes ''up'' through our field of view. You can get an idea of which direction is up or down by shining a small flashlight across the front of your telescope. Adjust the mount accordingly to point the R/A further west until movement stops.

If the R/A is too far '''West''' the star will appear to move '''South''' in the field of view.

Again, look at the path of the star (black arc) in the image below. The star appears to move ''down'' through our field of view, toward the southern pole. Adjust accordingly to point the R/A further east until movement stops.

Once we've got the azimuth alignment correct the star should no longer show movement in the field of view. This type of alignment can be very precise, but can also be quite time consuming to get dead-on. The image below shows the path of the star in relation to our field of view when the alignment is dead on.

==== Altitude adjustment ====
Once azimuth movement is minimized or stopped, point the telescope toward a star in the eastern sky (the western sky will work too, just reverse the directions given here). As with the azimuth adjustment if the R/A axis is not sufficiently angled the star will appear to move through the field of view.

If the star moves '''south''' in our field of view the R/A axis is pointed too '''low'''. As with the azimuth adjustment the path of the star moves according to the earth's rotational axis. In the image below you can see how the path of the star (black) moves through our field of view (red). Adjust the mount to increase the angle of the R/A axis until movement slows or stops.

If the star moves '''north''' in our field of view the R/A axis is pointed too '''high'''. Adjust accordingly until movement stops.

Once alignment is dead on the mount will be able to track the star without it moving in the field of view. See in the image below how the earth's rotational axis and our mount's R/A axis are aligned, therefore the tracking can follow the star.

And now we're hopefully done with drift aligning! If you're unable to get movement to stop completely in your first run through, you can repeat the process several times until you're happy with it.