Quote:
Originally Posted by skysurfer
Another disadvantage is that the two stars (Alpha Centauri and Acrux) are rather close to each other, compromizing the accuracy.
This also requires that both stars should be in the sky at all times which is not always the case in all SH.
Another method, apart from the polar scope method, using setting circles and a single star, max 30 deg altitude + zenith (or two stars at least 60 degrees apart) alignment has the same accuracy, which works worldwide, incl NH.
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Acrux and Rigel kent are about 15 degrees apart. That's not close. Secondly, accuracy has nothing to do with how close they are but to how carfully you place the lasers ON the stars. As the two stars form a triangle with SCP, if you determine two corners of the triangle, the third will be automatically determined.
Also, it is true that the two stars dip below 15 degrees from the horizon at certain times of the year, but because of the vible lasers, you may set up the device up to 40m away where line of sight is no longer a problem. The device can be easily customised for any other pair of stars.
From my experience, the setting circles method works only if you have very accurate gradations or encoders.