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Observatory Update: Drift Alignment

On 18 March, David Thompson and I returned to the observatory to verify last months handset based, polar alignment. We used the classic Drift Alignment method using stars at E/W extremes and south/meridian extremes. In this method the mount is slewed in an easterly direction for 60 seconds and then westerly for the same time. If properly polar aligned, an equatorial mount should return the star to the exact same spot in an eyepiece. At one time eyepieces with crosshairs were used for this but today cameras make the process a lot easier, and let you record the results. We connected a DSLR directly to the scope visual-back using the Celestron adapter, we did this to eliminate any misalignment that a poorly collimated diagonal may have introduced.


Drift alignment photo from the SCC Observatory: Flat line indicates perfect alignment

In the attached image the bright spot was the starting position where we held the star for 5 seconds, the light trail is the trail marked out as the star was slewed 60 seconds in each direction. The outward trace and the inward trace completely overlap one another indicating a very close alignment, a narrow horizontal V shape would have indicated misalignment. It would have been better if we’d had better “seeing” as the sharper the star image the more precise the information the test gives about the accuracy of the alignment. Still, we were very happy with the results we got!

Mike Bradley


We brought members of the public up to the observatory after Mike and David finished the drift alignment and had a great viewing session as the clouds opened up to give us a view of the sky. They got a glimpse of the moon, Jupiter and its moons, the Orion Nebula, and the double star Mizar/Alcor.

Charles Ennis


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