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Gemini Users Manual 22

2.4.4 Normal Operation

By now, you are no doubt eager to put Gemini through its paces. You can control your

mount using Gemini either from the Hand Controller or via a computer connected

through Gemini’s serial port. Chapter 5 describes these operations in great detail. The

present chapter concludes with a quick guide on how to use the Hand Controller to select

and GoTo objects in Gemini’s database.

2.4.4.1 Entering an Object of Interest

There are 2 ways to tell Gemini where you want it to go. The most common is to simply

select one of the thousands of objects from Gemini’s catalogs. However, if you want to

GoTo an object that is not in a catalog such as a comet, you can enter its RA and Dec.

coordinates manually using the commands in the “Coordinates” menu item.

Catalogs

Gemini has 11 permanently stored catalogs (databases) containing over 40,000 entries.

To select an object from a catalog, simply select the “Object Database” menu item. You

can then scroll through the catalogs using the DEC buttons; selecting one of the catalogs

then allows you to choose an object from that catalog.

Some catalogs such as the "Messier" and "NGC" catalogs require numeric entries to

choose an object. Other catalogs such as "Bright Stars" or "Solar System" allow you to

scroll through objects and select the object you want. In the case of the "Bright Star"

catalog, it is conveniently organized and subdivided according to the first letter of the

stars’ names. In all cases, once the object you want is displayed, press the RA+ button to

select it. A message is displayed, containing the object's distance to the meridian

(negative in the east) in minutes of time and the elevation in degrees.

Another way to acquire a catalog or object list is to compose it yourself. Using the

optional Gemini Control Center software, you can use your PC to prepare and download

your own catalog that can contain up to 4000 objects. This has the advantage of

including in your list only objects that will be used for a particular night's observation.

Coordinates

Another method of selecting an object is to enter its RA and Dec. coordinates directly.

Select “Coordinates→Enter RA/DEC” from the menu. You will then be shown the

mount’s current RA/Dec. location and be prompted to change each digit to the desired

coordinates. As with all numeric entries in Gemini, use the DEC+ and DEC- buttons to

change the flashing digit, the RA+ button to advance to the next digit, and the RA- button

to go back to the previous digit. After you have entered the last digit, press the RA+

button again to finish entering the coordinates.

By default, Gemini assumes that any coordinates you enter are for the epoch of the

current date. However, you can change Gemini’s default epoch to J2000.0 using the

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Equinox Systems GEMINI Manuel d'utilisateur Page 27