Drift Star Alignment Method

This is where you can read up the answers to some FAQs on astronomy and star-gazing in Singapore. Members' contributions are welcomed.
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weixing
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Favourite scope: Vixen R200SS & Celestron 6" F5 Achro Refractor
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Drift Star Alignment Method

Post by weixing »

You usually must have a telescope with a clock drive to use the drift star alignment method. The basic idea with drift star alignment is to let the telescope run and observe which way the star drifts. Note the direction of the error and correct by moving the mount of the telescope.

Step 1: Perform a rough alignment using compass or whatever.

Step 2: Choose a reasonably bright star near the meridian (the imaginary line running from the zenith to due south, or north for southern hemisphere observers) and near the celestial equator (zero degrees declination or 90 degrees down from the pole). It is best to choose a star within 5 degrees of this position. Aim the telescope exactly at this star using a reticle eyepiece. If you do not have a reticle eyepiece use your highest power eyepiece to allow you to see which way the star drifts. The finderscope does not generally have enough magnification for this task.

Step 3: Allow the telescope clock drive to run for a while, at least five minutes. The star will begin to drift north or south, any east/west error you see is probably the speed of your clock drive. It is up to you to figure out which way is north and south in the eyepiece, just move it up and down and observe the motion. Once you figure this out the rules below work for any telescope.
--If the star drifts north the telescope mount is pointing too far to the west.
--If the star drifts south the telescope mount is pointing too far to the east.

Step 4: Determine which way the star drifted and make the appropriate correction. This is done by rotating the entire mount east or west as needed. To make small corrections, many scopes have adjustment screws to allow this correction to be made with some precision.

Step 5: Point the telescope at a reasonably bright star near the eastern horizon and still near the celestial equator.

Step 6: Allow the telescope to run for at least five minutes possibly longer, the star will begin to drift north or south.
--If the star drifts south the telescope mount is pointed too low.
--If the star drifts north the telescope mount is pointed too high.

Step 7: Observe the drift and make the appropriate correction to the telescopes latitude adjustment.

Step 8: Go back and repeat from step 2 as necessary to get the needed precision.

Hope the above information is useful.... :)
Yang Weixing
:mrgreen: "The universe is composed mainly of hydrogen and ignorance." :mrgreen:
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