Dg280

[Rob Ram]

According to the FAQ,

"

Does the motor also adjust for variation in elevation on the dish for each satellite?
Yes it does."


How is elevation motion achieved? I see only one axis of motion, azimuth (east/west). The above FAQ implies two axis of motion; unless elevation is achieved by loosing a screw, make an adjustment by hand, then tighten the screw.
I am confused, any help will be appreciated.
Thanks.

[rainman]

If you look at the shaft it is curved so when you move a curve tube east and west it also will change elevation slightly. and also the motor is not aligned straight up and down but on a angle so when the shaft moves it is going from horizon to horizon.

[wejones]

According to the FAQ,

"

Does the motor also adjust for variation in elevation on the dish for each satellite?
Yes it does."

How is elevation motion achieved? I see only one axis of motion, azimuth (east/west). The above FAQ implies two axis of motion; unless elevation is achieved by loosing a screw, make an adjustment by hand, then tighten the screw.
I am confused, any help will be appreciated.
Thanks.

For once, I don't agree with what Rainman said, although it's pretty much a difference in semantics.

That bend in the shaft has nothing to do with changing the elevation. That bend in the shaft is only allow the dish mount to be adjustable to negative angles. Once set, the dish doesn't care if it's on a bent shaft or not.

Basically, with a polar mount you really aren't going to sats via azimuth elevation, you are going to the sats by hour angle and declination. Ie these mounts are similar to telescopes, and the motor shaft is almost (not exactly) parallel to the earth's axis, and as the motor runs, it changes the hour angle (similar to longitude) of the dish's aim. If we were all on the equator, since the sats are all in the equatorial plane, there wouldn't be any declination involved, but since we're not on the equator, we have to aim down a bit to see the sats, and these declinations vary in the range of up to 7 degrees, depending upon where you live. Basically, this is why you need the negative angle on the dish elevation, and why the bent shaft is needed, because dish mounts only adjust to positive numbers.

But basically, you'll notice that the motor shaft is tilted, so that it points to near the north star, and when the dish is aimed south, the actual elevation of the dish is at it's highest, and as the dish turns either to the east or west, the azimuth will be changing to the east or west, and the dish will be lowering in elevation toward the east or west horizon as an extreme.

Bottom line is that these are polar mounts not azimuth elevation mounts, which is why only one movement is reaquired.

[Rob Ram]

Bottom line is that these are polar mounts not azimuth elevation mounts, which is why only one movement is reaquired.[/quote]


Thanks for all replies.
I do believe you are correct, the DG280 is one axis with motor control only. Looking at the specification, one might get the impression that two motors, one for elevation and one for azimuth, are used to control the dish position. Would have been helpful, with limitations, for tracking the Moon (for Earth-Moon-Earth amateur radio use), non geostationary satellites (i.e. space station) or even geosynchronous satellites with a small wobble.