Hi all,
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In the first calculator (from Mel Bartels who pherhaps many of you already are familiar with) this question is asked:
"How long can an altazimuth telescope track with constant rates of speed in the azimuth and altitude axis?
An altazimuth telescope's drive rates vary continuously, more so in certain parts of the sky. Further, the rate of change in the drive rates changes. If the drive rates are left unchanged, eventually the tracking error will build to an unacceptable level. This calculator illustrates tracking errors. The error threshold and the time of constant drive rates can be varied."
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This may pherhaps explain why my tracking is not as accurate as in the beginning of an evening, since i so far have noticed this at high altitudes. (i have now noticed this in both azimuth and alititude axis). Correct me if i am wrong: Without Astrolock the calculated drive rate is accurate for the objects location in the sky at that very moment, which makes sense for a visual system not intended to track the same object within the same pixels for hours and hours. When looking at the screen the drive rates are fixed except when Astrolock is engaged do the numbers change. So in other words, a few hours later the calculated drive rate would be slightly different. Last night i switched of Nexus, pointed at Polaris and from there performed the 2-star alignment again. Slewed back to the object and now tracking was like in the begining of the evening again, i did after a while notice some altitude drift but I think I recentered without taking out the backlash properly or something. Highly unscientific test with too many variables pherhaps.??
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Next calculator:?
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"This calculator outputs the altazimuth coordinates along with the tracking rates and the change in the tracking rate. Use the change in tracking rates to determine when an update to the tracking rates is required. There are no corrections applied to the coordinates such as precession and refraction."
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Interesting stuff! I am fascinated by alt/az tracking theory!
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Gabriel?
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Gabriel Wiklund