Mount

Encoder Tics

GM 8

 4096

G11

 4096

HGM200

+8192

Although Gemini does not require encoders to function, there are some advantages to 

using them.  Encoders allow the system to keep track of the telescope's position even 

when you are moving the telescope manually with the clutches loosened.  Unless you 

have encoders, you should never loosen the clutches because to do so will cause the 

system to lose information both about where it is pointing, and about how close the 

mount is to the safety limits. The system must know where the eastern and western limits 

are, and when it has to make a meridian flip. Using encoders, the system is informed 

about manual movements and can take them into account, thereby avoiding exceeding the 

limits.  

The Gemini software is designed to give you the best of both worlds. As long as the 

position signaled by the encoders is consistent with the motor position within two 

encoder ticks, the far more accurate motor position is used. But if the encoders signal a 

change, the system trusts them and corrects its internal address values.  

When this happens, you see the characters R (for RA address correction) or D (for DEC 

address correction) displayed at the rightmost place of the system's display. This can be 

an indication of manual movement, mechanical slippage, or a wrong encoder resolution 

setup. 

Even if the encoders are set "Online" (per default or by selecting   Setup

Encoder

Use 

Encoder  ) you can use the system without the encoders being connected.  Encoder values 

are ignored until the first time a position change is signaled (the encoders are auto 

detected). On the other hand, you must not connect encoders while the system is running. 

If you intend to use them only at certain times, you can enable or disable them using the 

  Setup

Encoders   menu items.  

2.2.4  Power Requirements 

The Gemini System requires 12 18 Volts DC, 3 Amps to operate. You will need to have 

a battery or 

regulated

 DC power supply. Your choice of power supply is very important! 

Many DC power units are not regulated, provide too little current, and too little or too 

much voltage. This can cause problems with the Gemini. If you plan to run other 

equipment from the power supply, make sure it has enough additional capacity. 

Choose 

your power supply carefully to meet the requirements mentioned above

, and avoid 

potential problems such as long power cables. The Losmandy DC power supply 

(available separately) meets all the above requirements. 

2.3  Hand Controller Overview 

The Gemini System comes with the 

Deluxe Hand Controller

. All functions of the 

Gemini System are accessible using just the four diamond shaped buttons, and the 

Gemini Users Manual 

8