Example reduction - long method

The first observation is #70:

% reduce_switch
IN - Name of input file containing demodulated data > 19970807_0070
USE_CALIBRATOR - Should the data be divided by the internal calibrator /NO/ > 
SURF: run 70 was a PHOTOM observation of object 3C31
SURF: file contains data for 2 switch(es) in 1 exposure(s) in 20 integration(s)
in 1 measurement(s)
SPIKE_LEVEL - De-spike level /5/ > 
OUT - Name of output file to contain reduced switch data > red70
% change_flat
IN - Name of input file containing demodulated map data /@red70/ > 
SURF: run 70 was a PHOTOM observation of 3C31
NEW_FLAT - The name of the file containing the new flat-field > noiseflat.dat
% flatfield
IN - Name of input file /@red70/ > 
SURF: run 70 was a PHOTOM observation of 3C31
OUT - Name of output file > red70_flat
SURF: applying flatfield from noiseflat.dat
% extinction
IN - Name of NDF containing demodulated data /@red70_flat/ > 
SURF: run 70 was a PHOTOM observation with JIGGLE sampling of object 3C31
SURF: file contains data for 1 exposure(s) in 20 integration(s) in 1
measurement(s)
SURF: observation started at sidereal time 2 35 59.4417688 and ended at 2 52
07.164001
SURF: file contains data for the following sub-instrument(s)
 - P2000 with filter 2000
FIRST_TAU - First zenith sky opacity measured > 0.1
FIRST_LST - Sidereal time of first opacity measurement; hh mm ss.ss > 0
SECOND_TAU - Second zenith sky opacity measured > 0.1
SECOND_LST - Sidereal time of second opacity measurement; hh mm ss.ss > 0
OUT - Name of output NDF > red70_ext
% scuphot
IN - Name of input file containing demodulated data /@red70_ext/ > 
SURF: run 70 was a PHOTOM observation of 3C31
SURF: file contains data for 1 exposure(s) in 20 integrations(s) in 1
measurement(s)
ANALYSIS - Which reduction method /'AVERAGE'/ > 
OUT - Name of container file to hold map and time-sequence data > red70_phot
FILE - Name of ASCII file to contain results summary // > red70_phot.dat

The ASCII file, red70_phot.dat, contains the following:

 
% cat red70_phot.dat
Output from REDS reduction of a PHOTOM observation           
Reduction date        : Mon May 19 12:04:08 1997             
Observation definition: 3c31.obs                             
Date of observation   : 1996:8:7                             
Time of observation   : 15:52:07.659988                      
Run number            : 70                                   
Object                : 3C31                                 
Sub-instrument        : P2000                                
Filter                : 2000                                 
Centre coords         : RB                                   
Latitude              : +32:08:43.3                          
Longitude             : 01:04:39.10                          
Offset coords         : UNKNOWN                              
x offset              : 0                                    
y offset              : 0                                    
Sample coords         : NA                                   
Sky error removal     : FALSE                                
 							     
Photometric analysis  : AVERAGE                              
 							     
Bolometer: G6                                                
Weight:    1                                                 
 							     
Integration  Peak    Error       S/N      Peak_x     Peak_y  
   1    0.294E-04  0.461E-02    0.006  0.000E+00  0.000E+00  
   2    0.146E-03  0.461E-02    0.032  0.000E+00  0.000E+00  
   3    0.168E-03  0.460E-02    0.036  0.000E+00  0.000E+00  
   4    0.174E-03  0.461E-02    0.038  0.000E+00  0.000E+00  
   5    0.103E-03  0.459E-02    0.023  0.000E+00  0.000E+00  
   6    0.116E-03  0.460E-02    0.025  0.000E+00  0.000E+00  
   7    0.182E-03  0.461E-02    0.039  0.000E+00  0.000E+00  
   8    0.321E-04  0.462E-02    0.007  0.000E+00  0.000E+00  
   9    0.959E-04  0.462E-02    0.021  0.000E+00  0.000E+00  
  10   -0.481E-03  0.466E-02   -0.103  0.000E+00  0.000E+00  
  11    0.705E-04  0.466E-02    0.015  0.000E+00  0.000E+00  
  12    0.445E-04  0.496E-02    0.009  0.000E+00  0.000E+00  
  13    0.640E-04  0.468E-02    0.014  0.000E+00  0.000E+00  
  14    0.490E-04  0.470E-02    0.010  0.000E+00  0.000E+00  
  15    0.272E-03  0.469E-02    0.058  0.000E+00  0.000E+00  
  16    0.170E-03  0.471E-02    0.036  0.000E+00  0.000E+00  
  17    0.174E-03  0.471E-02    0.037  0.000E+00  0.000E+00  
  18    0.149E-03  0.473E-02    0.032  0.000E+00  0.000E+00  
  19   -0.609E-04  0.474E-02   -0.013  0.000E+00  0.000E+00  
  20   -0.874E-03  0.480E-02   -0.182  0.000E+00  0.000E+00  
 							     
Measurement results:                                         
 Parabolic fit to coadded jiggle:                            
        0.105E-03  0.385E-04    2.713 -0.170E+01  0.299E+00  
  Coadded result of individual integrations:                 
        0.312E-04  0.584E-04    0.534

The same procedure is repeated (not shown here) for #71 to produce the file red71phot.sdf. We can then combine the two observations using scucat:

% scucat
OUT - Rootname of files to contain concatenated data > 3C31_2000
IN - Name of input file containing photometry data > red70_phot
SURF: Found data for the following bolometers: g6
SURF: This is a PHOTOM observation of 3C31. There are 20 integrations
IN - Name of input file containing photometry data /!/ > red71_phot
SURF: Found data for the following bolometers: g6
SURF: This is a PHOTOM observation of 3C31. There are 20 integrations
IN - Name of input file containing photometry data /!/ >

We are now in a position to plot and despike the data (see Figure ). Note that the bolometer name, g6, will be appended to the file name giving 3C31_2000_g6.sdf.

% qdraw 3C31_2000_g6 mode=4 device=xwindows
NDF is 3C31_2000_g6
The default values have been adopted for parameter ABSLIM.
Current picture has name: DATA, comment: KAPPA_LINPLOT.
Using /home/jas/scuba/test/3C31_2000_g6 as the input NDF.
 
      Clip (+/-)         mean          std. deviation    Error in mean
      ----------         ----          --------------    -------------
                      0.800321E-04      0.276960E-03      0.437913E-04
         3.000        0.740715E-04      0.136353E-03      0.221194E-04

Clearly, this data set contains large spikes and the best despiking strategy is to remove the two biggest spikes that fall outside the 3$\sigma$ levels and then replot the data. For this we use the sigclip command.

Figure: Concatenated data for observations #70 and #71. The mean and plus and minus 3$\sigma$ levels are indicated with the dashed lines.

Figure: Concatenated data for #70 and #71 after removal of the two largest spikes with sigclip. The third spike is now excluded with a 3$\sigma$ clip and there are no further spikes at the 2.5$\sigma$ level.

%  sigclip 3C31_2000_g6 3.0
There was 1 element changed in the DATA array below the threshold.
There was 1 element changed in the DATA array above the threshold.
Clipped data written to 3C31_2000_g6_clip.sdf
%  qdraw 3C31_2000_g6_clip device=xwindows mode=4
NDF is 3C31_2000_g6_clip
The default values have been adopted for parameter ABSLIM.
Current picture has name: DATA, comment: KAPPA_LINPLOT.
Using /home/jas/scuba/test/3C31_2000_g6_clip as the input NDF.
 
      Clip (+/-)         mean          std. deviation    Error in mean
      ----------         ----          --------------    -------------
                      0.740715E-04      0.136353E-03      0.221194E-04
         3.000        0.890766E-04      0.101563E-03      0.166969E-04
% 
%  drawsig nsigma=2.5 device=xwindows
Current picture has name: DATA, comment: KAPPA_LINPLOT.
Using /home/jas/scuba/test/3C31_2000_g6_clip as the input NDF.
 
      Clip (+/-)         mean          std. deviation    Error in mean
      ----------         ----          --------------    -------------
                      0.740715E-04      0.136353E-03      0.221194E-04
         2.500        0.890766E-04      0.101563E-03      0.166969E-04

All three obvious spikes have now been removed and there are no further spikes down to the 2.5-$\sigma$ level (see Figure ). The source is detected at the 5.3-$\sigma$ level.