NavList:

I own several GoTo telescope mounts (iOptron), two of them with a built-in GPS and the most basic model without one. For the mount to work you need to input a position or have the GPS functionality. You mount your telescope on the unit, run through an initialization procedure and you can slew to an object in the control handset's database as well as track. These are alt-azimuth -- not equatorial -- mounts, so the on-board computer generates tracking rates for both axes continuously. The mount's control unit computes coordinate transformations, slews to objects, and generates the necessary tracking rates.

You can use these in a manual mode, and in that case you essentially have a theodolite. So you can measure the altitude (it reads out on the hand-controller) of a star, mark the time, and you have a star shot! An exercise in circular logic with the GPS, I know, but it's an exercise. And in the case of the non-GPS-equipped model, you can set the thing up, level the mount (and attached) telescope properly, turn it on and simply leave it in a manual mode. (You can also do this with the GPS-equipped models, just turn them on, leave them in manual control). In fact any alt-az telescope with digital setting circles (DSCs) can probably serve as a very good theodolite. I'll bet a few of the list members have telescopes. The nice thing about using your DSC equipped telescope as a theodolite is that you can choose a comfortable eyepiece, whereas with an actual surveyor's instrument you may not have much choice.

Another exercise with the GoTo scope: slew to a star and read the altitude and time, slew to another, and another, and you have a practice problem for sight-reduction. You can even do this indoors and do simulated slews. The hand controller indicates the star's altitude.

Jim
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