Line pointing at the HHT March 1997, D. Muders Line pointing provides a possibility to check the telescope pointing during heterodyne observations on the left flange where no bolometer is available. It can be mainly used with the CO 2-1, 3-2 and 4-3 lines observed towards evolved stars. A list of those sources is provided in the "Submillimeter Calibration" folder in the control room. Line pointing at the HHT is currently implemented via OBST and CHEF macros. There are two major versions. One is observing a PRASTER along azimuth and one along elevation. In OBST you have to type @TEL$OBS:LP e.g.: @TEL$OBS:LP 3 15 This will start two subsequent scans (first AZ then EL). If something fails, you can type in the PRASTER commands manually, e.g.: PRASTER /MAP 30 15 0 15 AZM/TIME 10 10/ON 3 for an AZ scan START or PRASTER /MAP 0 15 30 15 AZM/TIME 10 10/ON 3 for an EL scan START Please note the scan numbers as they will be required when reducing the line pointing. To reduce the observations, you have to run CHEF in one of FRANKENHEIM's windows (usually there is one with a yellow background). Type in CHEF and open a graphics window by typing DEVICE XL B or DEVICE I B in CHEF. At the very beginning create two files which are needed for the reduction. Type in CHEF: FILE OUT LPOI.SMT NEW FILE OUT LPOI.RED NEW Do this only once. The spectra will be written to LPOI.SMT. But since the standard CHEF reduction does not supply AZ/EL offsets, they have to be supplied by the reduction macro. Those spectra are written to LPOI.RED. Then call the reduction macro by typing @TEL$OBS:LPRF. The macro will ask you for the following parameters: WINMIN Lower limit for line window in km/s WINMAX Upper limit for line window in km/s MXMIN Lower limit for baseline window in km/s MXMAX Upper limit for baseline window in km/s AZSCAN Scan number for AZ scan ELSCAN Scan number for EL scan NUMOFPOINTS Number of points per scan SPACING Spacing between the points (arcsec) BASEORDER Order of baseline to subtract REDUCE Flag to indicate whether data needs to be reduced from raw data (YES or NO, see below) Select the windows according to the sample spectra in the calibration folder. Be careful about secondary lines other than the CO lines. Do not define the baseline window too large (a few hundred channels at most, CHEF may crash). The REDUCE flag should be set to YES only once. Otherwise it will confuse the reduction since the spectra appear multiple times in the LPOI.SMT and LPOI.RED files. If you want to rerun @TEL$OBS:LPRF (e.g. with different window sizes), use NO for the REDUCE flag. The macro will show you the AZ spectra and then pause. Whenever it pauses you can type C (CONTINUE) to go on. Then it will fit a gaussian to the line area calculated from the baseline subtraction. It will display the same for the EL scan. Eventually it will display the cross of spectra and then print the Delta(Col*) and Delta(Nule) values. If you like the fit, you have to add those values to the current Col* and Nule values displayed in the OBST window and enter them via the CORR command in OBST, e.g.: CORR -5.6 4.3. Besides the PRASTER line pointing there is also a 5-point WSWITCH line pointing macro. In OBST type in: @TEL$OBS:LPW This will start 5 subsequent scans. For now, those scans have to be made without interrupt. Otherwise the CHEF reduction macro will crash. In CHEF issue the same initial commands (DEVICE, FILE OUT...) if not yet done. Then call @TEL$OBS:LPWRF instead of LPRF. This macro will ask you similar questions like @TEL$OBS:LPRF except the number of points is fixed to 3 (along AZ/EL) and it wants just the number of the first of the 5 subsequent scans. The display and gauss fits will look like with @TEL$OBS:LPRF.