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Next Page: SPECTRUM/SPECPLOT - crude on-line data reduction

The Lexidata joystick and switches

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)

Notes

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 :

1. PROFILE

- The READ switch causes a profile to be drawn from the previous cursor position to the current position. Currently only horizontal and vertical profiles are permitted. The UP and DOWN switches control scaling - initially data is truncated at 16383 and DOWN halves the cutoff, UP doubles it

2. STATS

- The READ switch causes statistics of a rectangular neighbourhood of the current position to be listed on the terminal. These include a sky estimate based on the rim of the box, estimate of sky-subtracted flux, standard deviations and maximum/minimum pixel values within the box. The UP and DOWN switches control the box size - initially it is of side 11 and DOWN decreases it by 2, UP increases it by 2

3. LIST

- The READ switch causes the pixel values of a rectangular neighbourhood to be listed on the terminal. The box is the same one as used by STATS and its size is controlled in the same way using the UP and DOWN switches

4. ZOOM

- The READ switch causes the image to be zoomed about the current position with the current zoom factor. The UP and DOWN switches control the current zoom factor - initially it is whatever it was on entry to PHOTOM. DOWN decreases it by 1, UP increases it by 1

5. CURSOR

- The READ switch merely echoes the current position in pixel and user coordinates, plus the corresponding data value. In fact this information is given in all modes. The UP and DOWN switches control the box size in the same way as in the STATS and LIST modes

6. DIST

- The READ switch causes the distance between the current position and the last position to be calculated (in pixels) and listed on the terminal. The UP and DOWN switches control the box size in the same way as in the STATS and LIST modes

Parameters

There are some, but they should not normally be necessary when running within the CCD system.

Examples

Adam:> PHOTOM

Notes

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.