The program handles GEM mounts and their required meridian flip. It does so by changing the altitude and right ascension in low level functions. Right Ascension is rotated by 180 degrees. The altitude is mirrored across the pole so that a declination of 80 is an altitude of 100 degrees .After a flip, the altitude will read in the range of +90 to +180 to higher values (-90 to -180 and lower if in the southern hemisphere). The Declination and Right Ascension will be calculated and displayed correctly. The hand paddle buttons are not automatically swapped in case autoguiders are wired in. However, the hand paddle buttons can be swapped after the GEM flip by selecting the menu option 'flipbuttons' in the control section.
To do the flip automatically:
Either turn on autogemflip in the config.dat file, or via the menu option: motors | autogemflip. The meridian flip will occur automatically, starting with a move to the pole, followed by the move across the meridian, ending with the move from the pole. You will have to cancel each slew in sequence if you wish to abort.
Or, select the menu option: move | gemflip.
To do the flip manually:
Turn off tracking.
Select the GEM flip menu option.
Position the telescope in declination so that the tube is roughly pointing at the celestial pole, for instance, a declination of 80+ degrees (-80 degrees if in the southern hemisphere).
If using the hand paddle to position the scope, or encoders are operational, the Ra and Dec should agree with the equatorial coordinates displayed before starting the GEM flip.
Move the scope 180 degrees in azimuth or 12 hours in right ascension.
Move the scope across the pole in Declination until the scope is roughly pointed properly.
Re-center the object.
If the hand paddle was not used to position the scope, or no encoders are present, you must do a 'reset to equat' to set the altazimuth coordinates properly.
The altitude will display a reading greater than 90 degrees (southern hemisphere users will see a reading below -90 degrees), and the Declination will display a reading less than 90 degrees (southern hemisphere users will see a reading greater than -90 degrees).
Tracking and goto functions can be resumed.
Hand paddle up down buttons can be reversed if desired by going into the menu section: control and selecting the flipbuttons option.
Program startup and shutdown:
You may start with the scope on either side of the meridian, and end with the scope on either side of the meridian. It is preferable to end with the scope on the same side of the meridian that you expect to start next time with. If you do not, read the next section.
Synchronizing software and telescope to same side of meridian: