# Max vel az/za  vs za (speed on the sky)

#### dec, 2002

The maximum encoder speed for the azimuth is .4 deg/sec while the dome can move at .04 deg/sec. Since the azimuth is not a great circle (cutting through the center of the celestial sphere) the angle on the sky for azimuth motion is  encVelAz*sin(za).
The maximum za velocity of .04deg/sec = 2.4 arcminutes/sec on the sky.

When planning a mapping run you need to take into account the maximum velocities in az, za for a fixed velocity on the sky. The plot shows the ratio of maximum zaVel/azVel az measured on the sky versus za.are planning a mapping observation you need to know how fast the azimuth will have to go for a constant angular velocity on the sky.

From the plot you can see that the sky velocity in az,za is equal at 5.6 degrees za. Above this, the azimuth can move faster, below this the za can move faster.

If you want to map at 1/2 slew rate (1.2 arcmin/sec in za), the  smallest za you could use would be za=2.8 where the za is twice the az sky veloicty. Here the dome would be moving at .5 slew while the azimuth is moving at slew rate.

`plotting  : x101/misc/azzaspeed.pro`
` home_~phil`