#
# abbans.pro
#
# Usage: call abbans size1  npairs
#
# Take a abba seq of spectra North-South. The offset is size1 arcsec. 
# The script repeats npairs times. I.e. each pair 
# consists of 4 integrations, 2 at a, two at b. 
#

	ask 'What is the desired NS offset (arcsec)?' size1
	ask 'Number of pairs?' npairs

 	call askpars
	
#
# this is the basic step (offset is always NS - the most efficient 
# offsetting dir. )
#
	stepn=size1
	stepe=0.0

	printf 'stepn is %f7.2 ' stepn

	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

	yorn 'Disable the Tip Tilt guider during offsets'
        if (yorn==1)
          usetip=1
        else
          usetip=2
        end_if

#
# begin sequence
#
	do j=1,npairs

#
# position a
#
	  avego $coad
	
#
# position b
#
	  if (usetip==1)
            call ttd
          end_if
          offset ra=stepe dec=stepn 
          if (usetip==1)
            call tte
          end_if
	  avego $coad
#
# position b
#
          avego $coad
#
# position a
#

	  if (usetip==1)
            call ttd
          end_if
          offset ra=stepe dec=-stepn
          if (usetip==1)
            call tte
          end_if
          avego $coad
	
	end_do

	alert 'SCRIPT COMPLETED' 3 1

return