(g) Brightness of Display Setup 

The user can adjust the brightness of the Hand Controller's LED display. 

(h)  Geographic Location Setup 

The user can either input the mount's longitude and latitude manually, or achieve the 

same thing automatically, including setting the mount's UTC Date/Time and Time Zone 

via a GPS receiver connected to Gemini's serial port. 

(i) Coordinate Epoch 

The user can determine the equinox of any coordinates used by Gemini.  This selection 

applies to coordinates transferred to and from planetarium and other telescope control 

software as well as coordinates entered directly by the user.  Either J2000.0 or the 

Equinox of the Date can be selected. 

Control Features 

(a) Telescope Alignment 

Gemini automatically initializes its celestial coordinate system when it is powered in the 

standard startup position (counterweight shaft down and OTA pointing to the celestial 

pole).  This permits Gemini to GoTo (with reasonable accuracy) a first alignment star 

(Initial Alignment).  A list of Bright Stars that are currently above the horizon is 

provided; selecting one of the stars triggers a GoTo operation. Additional star alignments 

can then be performed in order to develop and refine a computerized pointing model for 

greater GoTo accuracy.  Under certain circumstances (e.g. changing eyepieces, rotating 

diagonals, etc.), stars found and slewed to by the Gemini are no longer centered in the 

eyepiece.  To adjust for this occurrence, Gemini includes a synchronization feature that 

allows an object to be re centered without changing the pointing model.  Finally, Gemini 

includes a polar alignment assistance feature, and a Polar Axis Correction feature; the 

latter requires that a pointing model first be established.  

(b) Telescope Movement 

Gemini allows tracking in 6 speeds: Sidereal, Lunar, Solar, Adaptive King Rate, Closed 

Loop, Comet/User Defined, and Terrestrial (tracking turned off).  In addition, the Hand 

Controller permits the user to move the telescope in both RA and Dec in 3 speeds that are 

established in the setup menu:  Guiding, Centering, and Slewing.  The user can also 

perform GoTo movements of the telescope at a separate speed that is also established in 

the setup menu.  When a GoTo operation occurs, the telescope moves at GoTo Speed, 

and then slows down to Centering Speed as it approaches its target.  Telescope parking is 

a separate command that disables tracking and moves the mount to a predetermined 

Home position   by default, counterweight down with the telescope pointing to Celestial 

North.  Finally, all telescope movement stops and an alarm sounds when the mount slews 

to either its Eastern or Western safety limit.  A separate warning sounds when the mount 

approaches its Western limit while tracking. 

Gemini Users Manual 

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