Re: Getting the Tripod pointing toward true north #EXOS2 #polaralignment

Jerry Hubbell - Explore Scientific VP Engineering

On Mon, Mar 2, 2020 at 11:24 AM, Timothy Myers wrote:
I still wondered why the mount  moved so slow but found that the speed could be adjusted up to 650 I still do not know what 650 number represents. Was wanting to inform Wes since he had asked about the speed. I am still curious as to what the up and down arrows to the left of the manual slew buttons is for, in CDC.
Those buttons are just as you say they are... manual slew buttons. They use the ASCOM API MOVE method to move the mount in the corresponding direction at the sidereal rate multiple.  The numbers from 1 to 650 denote the sidereal rate multiplier.  The PMC-Eight is internally restricted to 40,000 x step resolution, which is 40,000 x 0.3125 arc-seconds/sec for the EXOS 2, or 12,500 arc-seconds/sec or 3.47 deg/sec. This is also equal to 833x Sidereal Rate. 650x the Sidereal Rate is 2.7 deg/second.  The problem is that the ASCOM API Move method does not ramp the rate up, it is an instantaneous move, so there is a chance that at the faster rates, the inertial load will exceed the applied torque and the motor will skip steps and you would probably hear it happening, depending on what equipment you have loaded on your mount.

The up and down arrows to the left of the slew buttons look more like chevrons. They are used to flip the button directions on each axis. If you position your mouse pointer over the chevrons, it will pop up a description.
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at
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