Without optional encoders installed, all movements of the telescope must be done 

electronically, with the RA and Dec. clutches tight so that no slippage of the OTA can 

occur.  Although not necessary for operating Gemini, optional encoders are useful 

because, if they are installed, you can loosen the axis clutches of your mount, and move 

the telescope to any position by hand without Gemini losing track of where the telescope 

is pointing. 

The first items of this menu, "EncRes RA" and "EncRes DEC," enable you to define the 

axial encoder resolutions.  The RA and DEC encoders may have different resolutions, 

and each may be up to 32,768 ticks/revolution.  In general, the sign is "plus" if the 

encoders are moved in the same direction as the axes, and "minus" if the direction is 

reversed by a gear.  Setting up the encoders incorrectly will result in unwanted behavior 

of your system, in which case 'R' or 'D' will be displayed at the right side of the display, 

indicating a correction to the internal position counters caused by and derived from the 

encoder data. 

The "Test Encoder" menu item displays the actual values of both encoders, and can be 

used for testing if you are connecting your encoders for the first time.  One revolution of 

an axis should bring the counter back to the same value.  This is easily tested for Dec. but 

for RA, you can only move between the mechanical limits of your mount. 

"Use Encoder" is a toggle.  Selecting it once causes Gemini to ignore the encoders even 

though they are connected.  Selecting it a second time sets the encoders online again. 

5.3.10.4  Alarm Timer 

Alarm On

Alarm Off

Set Alarm Time

These functions allow you to use the Gemini as an alarm timer.  The time for sounding 

the alarm (useful for determining when to close a camera's shutter) is set in UTC.  

Although the alarm time remains stored in Gemini's real time clock (RTC), it is always 

set to "off" after powering up.  You can activate the alarm by executing "Alarm 

Timer

Alarm On" and can disable the alarm by executing "Alarm Timer

Alarm Off." 

5.3.10.5  UTC Date/Time  

Starting with Level 3 version 1.01, you are able to change the UTC Date (date and time) 

immediately after a Cold Start.  Refer to section 2.3.2.1 Cold Start Setup Options for an 

explanation of how this is done. 

The  "UTC Date/Time" menu item is where you set Gemini's real time clock (RTC).  

Upon executing "UTC Date/Time" the UTC date and time display freezes but the RTC 

continues to keep time. 

Gemini Users Manual 

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