#
# slitscan.pro
#
# Usage: call slitscan size1 n nscans
#
# Take a scan of n spectra along the slit evenly spaced by size1 arcsec. The 
# star should be centered along the slit. The telescope is returned to center 
# after the slit scan. Requires the correct value of the rotator angle to be 
# set by zcenter.pro. Rot is given in degrees. Repeat the scan nscans times.
#
parameter size1 n nscans

	yorn 'Disable the tip tilt guider during offsets?'
	if (yorn==1)
	  usetip=1
	else
	   usetip=2
	end_if

	if (n==0.0)|(size1==0.0)
	  ask 'Number of spectra to take along slit?' n
	  ask 'What is the separation between spectra (arcsec)?' size1
	end_if

	if (nscans==0)
	  ask 'Number of scans?' nscans
	end_if

 	call askpars
	
	theta=271.5-rot
#
# this is the basic step
#
	stepn=size1*sind[theta]
	stepe=size1*cosd[theta]
#
# set to the end of the slit from the middle or middle from the end
#
	on1=(1-n)*0.5*stepn
	oe1=(1-n)*0.5*stepe

	yorn 'Are the OBSERVE params OK and TELESCOPE centered'

        if (yorn~=1)
	  printf 'Aborting sequence: reset parameters/center telescope'
	  printf 'and try again'
	  return
        end_if
#
# begin sequence
#

	do j=1,nscans
	  if (usetip==1)
	    call ttd
          end_if
	  offset ra=oe1 dec=on1 twait=0
	  printf 'offset %f6.2 %f6.2' oe1 on1
	  if (usetip==1)
	    call tte
	  end_if

	  avego $coad
	
	  do i=1,n-1
	    if (usetip==1)
	      call ttd
	    end_if
	    printf 'offset %f6.2 %f6.2' stepe stepn 
	    offset ra=stepe dec=stepn 
	    if (usetip==1)
	      call tte
	    end_if
	    avego $coad
	  end_do
#
# return to center
#
          if (usetip==1)
  	    call ttd
	  end_if
	  printf 'offset %f6.2 %f6.2' oe1 on1
	  offset ra=oe1 dec=on1 twait=0
	  if (usetip==1)
            call tte
          end_if
	
	end_do

	alert 'SCAN COMPLETED' 3 1

return