Subsystem 3 (Programming logic) - Telescope Over the Internet

The Login screen

The user is presented with a web interface. The interface is designed so that the user can select an object he or she wishes to view from the data base provided or manually input the celestial coordinates. He/ She is also privileged to select Sun, Moon and planets for which the ephemerides of that particular time will be automatically calculated. Initially the algorithm to convert of RA/ DEC celestial coordinates to HA/DEC Equatorial coordinates is implemented in the client side using javascript. This conversion takes the longitude, latitude of the telescope, celestial coordinates of the object to be viewed and local time as inputs and calculates the local sidereal time, from which the HA is calculated. If the user selects one of the closest objects then the ephemerides of that object for that particular time is calculated in javascript prior to the conversion algorithm

The Telescope controller screen

Resulting HA is used to check if the particular object can be viewed from the location of the telescope. If not an error message is displayed to the user saying that this object cannot be viewed as it is out of the visible sky. When the above test is passed, the current coordinates of the telescope is read from the server and resultant degrees to be turned is calculated in the serverside program which is implemented in ASP.NET/C#. This result is transmitted to the main controller through the RS232.Then the current location of the telescope is saved in the server.

Manual fine tuning is also provided if the celestial object doesn’t come within the center of field of view. User can manually rotate the telescope with a certain amount in HA/DEC to manually fine tune.

The telescope is calibrated initially to point the North and Zenith and these coordinates are defined as (0,0). The coordinate system of our telescope takes these as the reference point. After the initial turn the telescope rotation compensates for the earth rotation as well. That is, the time elapsed from the previous command to the present is calculated and HA rotation is compensated accordingly. Also for every rotation, time taken for the rotation is calculated based on the steps to be turned and it is compensated with additional steps. After the object is in the center of the field of view, the earth synchronous system compensates the earth movement and keeps the object steadily in the center.

The CCD Controller screen

Extensive testing has been done to find out the backslash in the gear system in varies positions of the telescope. This backslash has been compensated with necessary steps in the programming logic




















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