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The Lexidata joystick has six switches. These are labelled, from left to right, EXIT, MODE, DOWN, RESET, UP and READ. All Lexidata programs that use the switches light up only those which they use and give each switch an interpretation which is in the general spirit of its label. The general meanings are :
1. EXIT - Exit from the program 2. MODE - Cycle through various options presented by the program 3. DOWN - Decrease some quantity or quantities 4. RESET - Reset some quantity or quantities 5. UP - Increase some quantity or quantities 6. READ - Read the cursor position (Blue button)
It is always the change in state that is important, never the actual position of the switch.
There are six modes of operation, and the MODE switch is used to cycle through them. The initial mode is ``Profile'', followed by ``Stats'', ``List'', ``Zoom'', ``Cursor'' and ``Dist'' respectively. The RESET switch always unzooms the image and sets everything back to its default value. The EXIT switch always causes immediate program exit.
The behaviour of the remaining switches, READ, DOWN and UP, is described for each mode :
There are some, but they should not normally be necessary when running within the CCD system.
PHOTOM, in common with all the Lexidata programs, will automatically use the current image, i.e. the one that has most recently been read from the CCD.
PHOTOM uses the BIAS value given at startup when it estimates line centres. A better value can be estimated using PHOTOM in STATS mode or else the STATS utility. BIAS can be updated using the BIAS command.
The pixel coordinates of the last two points selected in PHOTOM are written as ACL variables PHOTOM_PXX1, PHOTOM_PXY1, PHOTOM_PXX2 and PHOTOM_PXY2. Thus PHOTOM can be used in a procedure as an easy way of getting two points selected by the user.