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Old 04-01-2015, 03:48 AM
adman (Adam)
Seriously Amateur

adman is offline
Join Date: Sep 2009
Location: Brisbane
Posts: 1,279
Hi Frank!

Drift alignment is one of the best ways to get a decent polar alignment, but it does take a bit if practice. It is best done with a camera using something like PHD / PHD2 or backyardEOS or astrophotography tool (APT) as you can very quickly determine which way the star is drifting so you can make your correction. Have a google around and you will find some good resources.

I found it was useful to have a good mental picture of what you are doing at each stage of drift aligning - basically there are two imaginary lines that you are trying to line up. Imagine for a moment that your telescope is a giant laser, then imagine the arc it would describe in the sky as you rotate it around its RA axis. That is your first line. The second line is the actual track of a star, and the arc it describes as it moves from east to west.

The only adjustments you have at your disposal (assuming your mount is level) are azimuth (spinning your mount around a vertical axis) and elevation (the angle your RA axis makes with the horizontal). Then imagine how those two imaginary arcs would differ if you are misaligned in either azimuth or elevation.

To align your mount in elevation, point your scope to a star lowish in the east. If your are properly aligned in azimuth the arc your telescope would describe will be the same as the star. If your elevation is too high your telescope will start to point to the north of the star - so the star will appear to drift south. Conversely if your elevation is too low, the star will appear to drift north.

Then to align in azimuth, point your scope to a star on the celestial equator near the meridian :ie straight up and a bit to the north. If your mount is pointing slightly west of South, the star will drift south, if it is pointing slightly east of South, the star will drift north.

There is a good description on IIS (google basics of drift alignment) of this and some good youtube videos that help you to get the mental picture right - once you have that it all makes sense. Keep at it though it does get easier

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