# Sidereal tracking rates for Mauna Kea

In testing the performance of antenna servo systems for low velocity tracking (at the specified minimum smooth velocity), it is useful to know the directions in the sky where the tracking velocity crosses zero. For elevation this is simple: at transit (az=0 or 180), but for azimuth it is more complicated. The azimuth tracking rate goes to zero only for objects that transit between the zenith and the celestial pole. Using the equations from the CBI website, here are plots of the locations of zero crossings in the azimuth sidereal tracking velocity from Mauna Kea. Click the image for a larger version.

The following plots show the azimuth tracking rate for 16 minutes centered on the zero crossing for 6 different declinations between the zenith and the celestial pole:

The following plots show the elevation tracking rate for 16 minutes centered on transit for 15 different declinations.

The associated C programs and python scripts that generated these plots are attached below.

-- ToddHunter - 2013-01-06

Topic attachments
I Attachment Action Size Date Who Comment
txt azelratesort.py.txt manage 3 K 2013-01-06 - 01:38 ToddHunter python pylab script to plot the output files from azelrate.c
txt elrates.py.txt manage 2 K 2013-01-06 - 01:38 ToddHunter python pylab script to plot the elevation tracking rates near transit
txt azrates.py.txt manage 2 K 2013-01-06 - 01:42 ToddHunter python pylab script to plot the azimuth tracking rate near the zero crossing for 6 different declinations
png azelrate.out.sma.sort.png manage 159 K 2013-01-06 - 01:37 ToddHunter plot of the locations of zero azimuth tracking velocity from Mauna Kea
png elrates.png manage 260 K 2013-01-06 - 01:33 ToddHunter elevation tracking rates for Mauna Kea near transit for 15 different declinations
c verify.c manage 37 K 2013-01-06 - 01:23 ToddHunter C program to compute the az/el position and velocity track of an object across the sky
c azelrate.c manage 10 K 2013-01-06 - 01:21 ToddHunter C code to compute az/el tracking rates throughout the sky
png azrates.png manage 221 K 2013-01-06 - 01:41 ToddHunter azimuth tracking rates for Mauna Kea near the zero velocity crossing for 6 different declinations
This topic: Main > TWikiUsers > ToddHunter > MaunaKeaSiderealTrackingRates
Topic revision: 2013-01-06, ToddHunter
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