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Optical Pointing using MNU

MNU includes a mode for optical pointing, accessible through the REFLECTOR page:

C.SYS Tracking
Second. Mirror
In this mode, activated by the POINT key (PF3 on the REFLECTOR page), it tries to find the best candidates to map the sky uniformly in azimuth and elevation. The density of stars is given by specifying the minimal distance angle between stars, using the GOLD/DISTANCE (PF1/KP2) key. To hasten a pointing session, the program will try to find candidates above 10 degrees in elevation and at the minimum distance (in time) from the current telescope position.

MNU uses a catalog of bright stars named J2000R.CAT in the [CONTROL.COMMAND] directory, on disk COMP$DISK:, and writes the pointing data in the most recently created Date.OPT file on directory [OBSERVER.POINTING], on disk RLTDATA (Date being a date in format DD-MMM-YYYY as usual). The file POINTING.OPT, also in [OBSERVER.POINTING], contains the name of the last pointing data file created along with its creation time. MNU assumes that the pointing concerns the default antenna. To find out or modify this default use the DCL command DEF [Ant], or use the GOLD/DEF (PF1/PF1) key to change it.

To start an optical pointing session, press the POINT key. The program opens the data file Date.OPT, reads and processes the records concerning the default antenna, and then closes the file. It opens the catalog file J2000R.CAT and processes the star coordinates in order to prepare and to speed up the calculations next to be performed. Next, the file is closed.

Specify a minimum distance between stars using the GOLD/DISTANCE key, for instance 10.0 for 10 degrees. MNU will look for the best candidate, given the present telescope position, the data already saved in Date.OPT, and the possible stars in the catalog file. To move to the next star, press the NEXT (KP2) key.

When the telescope stops slewing and tracks the star, use MNU to move the telescope slightly so the TV cross-hair is on the star. Meanwhile, as soon as the command to send the telescope to the requested position has been spawned, the catalog is searched for the next star candidate. Once the TV cross-hair is on the star, press the SAVE (KP1) key to append the star position, the current telescope position, the sidereal time and the refraction correction to the data file. If an error occurs while opening the file, the operation can be executed again.

Then go on using the NEXT key... Every time you press the NEXT key, a message saying ``No more candidate'' may appear. You should then either suspend your pointing sessions using the GOLD/STOP (PF1/PF3) key, or decrease the minimal distance between stars using the GOLD/DISTANCE (PF1/KP2) key.

next up previous contents index
Next: Reducing data Up: Optical Pointing Previous: Getting data   Contents   Index
Gildas manager 2020-03-29