6.7.3 LWPOINT

OBST> LWPOINT <ref_long> /DEFAULT
		/LENGTH_LPT <arcsec> 
		/TIME_LWPT <Time per point (in seconds)
		/NUMBER_LWPT <number of points along an arm> 
		/SUB_LWPT <number of total repeats> <by_2> 
		/NOOFFSET
		/ORIENTATION <direction (L, B, A, E)> <only>

LWPOINT performs a cross with a given number of points per arm, using spectral line observations (WSWITCH).

• <ref_long> The wobble throw (in arcseconds). It will be compared against the current wobbler settings and a warning issued if the two do not match.

ADVERBS:

• LENGTH_LPT is the real-angle length of the arm(s) of the cross in arcsec. For point sources, 3 to 4 half power beamwidths is a good choice. As a rule of thumb at the HHT, 25 $\times \lambda_{mm}$ yields the HPBW in arcsec.

• TIME_LWPT is the integration time for an individual subscan along an arm.

• SUB_LWPT is the number of times you repeat each portion of the cross. If you add BY_2, then the scanning coordinate is changed after 2 subscans.

• NOOFFSET By default, the field center is offset by the parameters of SET OFFSETS. If /NOOFFSET is part of the observing command, the field center is the unshifted object selected by the SOURCE command.

• ORIENTATION This ADVERB has 2 parameters.

  The first, <direction (L, B, A, E)>, determines the coordinate system, while the second, <only>, dictates which of the coordinates is to be used for the first subscan. Only the first character of <direction (L, B, A, E)> is tested, the following values being legal,

  E = Relative AZ/EL, starting with elevation
  A = Relative AZ/EL, starting with azimuth
  B = Scan in LAM/BET of the SOURCE basis system, starting with latitude BET
  L = Scan in LAM/BET of the SOURCE basis system, starting with longitude LAM.

  The first character of the second parameter is tested. If this is an O for ONLY, the subscans can be made in just the starting coordinate selected by <direction (L, B, A, E)>. In all other cases normal cross scans are executed.

EXAMPLE:

OBST> LWPOINT -120 /NUM 5 /TIME 15 15 /LEN 60

Will observe 5 points on each arm spaced by 60 arcseconds (at -30, -15, 0, 15, and +30'' per arm). The wobblerthrow is at (-120''). This would correspond to a wobble position of (-60'',+60''). The integration time per point is 15 seconds.

CHEF NOTES:

The LPOINT observation is reduced and displayed in the online display (CHEF). It subtracts a baseline of order 1 off all spectra and calculates the line area. It needs specific velocity windows to do that. Those windows are specified in the catalog using the OBSINP commands VLOW, VHIG, WLOW, WHIG.

See LPOINT for details on CHEF use.