If the FITS file contained a full set of World Coordinate System (WCS) FITS key words, then it is possible to specify the position in terms of RA and Dec.
If you have an image displayed, then lextrct prompts for a position using:
Cursor, or Pixels (P)?
If you enter a P then lextrct will ask you for a pixel location as X,Y coordinates. Likewise if you enter C, Lextrct will activate the PGPLOT cursor and you will move the cursor to the location you want and click. Lextrct does not list options that are not valid, thus is you have not displayed the image or the PGPLOT device does not support a cursor the prompt is reduced to
Pixels (P)?
to indicate that only a pixel can be entered at that point.
Lextrct remembers the last location you entered and that is the default.
Note, lextrct allows you to type answers to following questions without being prompted. Thus at the "Cursor, or Pixels (P)?" prompt, it is possible to enter "P 1023, 200". If you do this then lextrct will read the 1023,200 as the pixel location and not prompt you again for a pixel position. This feature is carried to extreme in the BOunds command where the single input line of
bo s p 1023,300 10 y s 1023,300 100
would enter all the data BOunds needs. A useful feature is that you can enter more than one cursor command on the command line and thus avoid toggling back and forth between the graphics device and the terminal. Thus the following
bo r c c y r c c
will allow you to click on the graphics device 4 times to define the corners of two rectangular bounds.