Number of Subscans

Due to a limitation in the maximum number of files opened in cfitsio (300 in the APECS-1.0), the maximum number of subscan readable in Boa is 99.

Use continuous_data 'on' to observe as much as you want with one single subscan
However, if you observe moving objects, their coordinates are only computed once per subscan

Observing Tips

In the following, you can start the specified macro.apecs by typing run_macro('macro.apecs') at the APECS prompt, or when function are defined execfile('macro.apecs') . A set of useful abbreviations have been defined in the abb.apecs macro.

Contents

Number of Subscans
Observing Tips

How to setup your observing session

The setup-laboca.apecs macro has to be launch at the beginning of each observing session :

   1 #SET PROJECT ID
   2 project_id('your ESO project ID')
   3 
   4 #SET FRONTEND - BACKEND
   5 frontends 'LABOCA'
   6 laboca.backends 'abba'
   7 
   8 #SELECT USED CHANNELS AND REFERENCE PIXEL
   9 laboca.feeds select='all',ref='default'
  10 
  11 #SET FRONTEND GAIN
  12 laboca gain=4
  13 
  14 #SET BACKEND GAIN AND DUMPTIME (200Hz)
  15 abba dumptime=0.005, gain=10
  16 
  17 
  18 #SWITCH OFF USE OF REFERENCE 
  19 use_ref 'off'
  20 
  21 #SWITCH CONTINUUS DATA TAKING OFF
  22 continuous_data 'off'
  23 
  24 #SET DEFAULT CATLOG FOR 2nd CALIBRATORS AND POINTING SOURCES:
  25 sourcecats(['POINT.cat','Your catalog.cat'])

Observe with a few feeds only

Once you have determined which feeds are dead, noisy or non responsive, you can select only a set of good bolometers to observe with. For example, you can setup a good_chan.apecs file as :

This following is for illustration only

   1 center_chan = 318
   2 
   3 sky_chan= [  1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,  14,  15,
   4              16,  17,  19,  20,  21,  23,  25,  26,  27,  28,  31,  36,  38,  39,
   5              41,  42,  43,  44,  45,  48,  49,  50,  51,  52,  54,  55,  56,  57,
   6              58,  61,  62,  63,  65,  67,  68,  70,  71,  72,  73,  75,  76,  77,
   7              78,  79,  80,  81,  82,  83,  84,  85,  86,  89,  90,  91,  92,  93,
   8              94,  95,  96,  97,  98,  99, 100, 101, 102, 103, 104, 105, 106, 107,
   9             108, 109, 110, 111, 112, 113, 114, 115, 116, 119, 121, 122, 123, 126,
  10             127, 128, 129, 131, 132, 133, 134, 136, 137, 138, 139, 140, 141, 143,
  11             147, 148, 149, 150, 153, 154, 155, 156, 157, 159, 160, 161, 162, 163,
  12             164, 165, 166, 167, 168, 169, 175, 176, 177, 178, 179, 180, 181, 183,
  13             184, 185, 186, 187, 191, 192, 194, 196, 198, 202, 203, 205, 207, 209,
  14             212, 215, 216, 217, 218, 219, 220, 221, 223, 225, 227, 228, 233, 234,
  15             236, 237, 238, 239, 240, 244, 245, 246, 249, 253, 255, 256, 257, 258,
  16             259, 262, 263, 264, 265, 267, 269, 270, 271, 274, 278, 279, 281, 282,
  17             283, 286, 288, 290, 291, 292, 296, 298, 303, 310, 313, 314, 316, 317,
  18             320]
  19 
  20 dark_chan= [29, 33, 35, 40, 64, 66, 124, 135, 142, 144, 146, 151, 158, 189,
  21            193, 195, 200, 224, 226, 284, 295, 302, 304, 306, 311]
  22 
  23 
  24 good_chan = []
  25 good_chan.extend(sky_chan)
  26 good_chan.extend(dark_chan)
  27 
  28 beam_chan = []
  29 beam_chan.extend(sky_chan)
  30 beam_chan.append(center_chan)
  31 
  32 small_chan = [1,9,10,11,17,19,110,121]
  33 small_chan.extend(dark_chan)

and changing the setup-laboca.apecs as

   1 [..]
   2 #SELECT USED CHANNELS AND REFERENCE PIXEL
   3 execfile('good_chan.apecs')
   4 laboca.feeds select=good_chan,ref='default'
   5 [..]

you will only get data for a subsample of the array, lowering the used disk space and the time needed to read them. If you want to make tests on the array, you can also use a very small subset of the array as laboca.feeds select=small_chan,ref='default'

Selecting the reference pixel

You can select which feeds will be the reference pixel for your observation. To simplify the process you can define functions like :

This following is for illustration only

   1 def ref110():
   2         laboca.feeds (select=beam_chan,ref=110)
   3 def refcenter():
   4         laboca.feeds (select=beam_chan,ref='default')

to select, as reference pixel, the feed 110 or the default, respectively.

Pointing

Crosses

Regular cross pointing scans are possible, but produce highly undersampled coverage on the sky. We recommand to use spiral strokes for pointing, producing fully sampled coverage on the sky for the complete field of view of the array.

Spirals

It is possible to use spiral strokes to make pointings with Laboca. A function pspiral(time=20.0) has been setup as follow in the abb.apecs file:

be sure to select a valid reference channel, although not critical

   1 def pspiral(time=20.0):
   2         use_spiral ('on')
   3 
   4         # Define the spiral stroke : 200 Hz sampling
   5         spiral_setup(r0=0, r_dot=3, phi_dot=120, dumptime=0.005, \
   6                      r0_unit='arcsec', r_dot_unit='arcsec/s', \
   7                      phi_dot_unit='deg/s',dumptime_unit='s')
   8         
   9         # point scan in raster mode, 1 spiral, 20s
  10         point(time=time,mode='ras',points=1)
  11         use_spiral ('off')

Focus

Focus can be made with standard APECS focus() command

be sure to select a valid reference channel

   1 focus(amplitude=0.8,time=5,points=5,axis='Z',mode='sym')
   2 focus(amplitude=2.0,time=5,points=5,axis='X',mode='sym')
   3 focus(amplitude=2.0,time=5,points=5,axis='Y',mode='sym')

The focus scans will be reduced by the onlineCalibrator. The correction offsets can be applied by using the fcorr() command :

   1 fcorr('f')

Skydip

In order to make a opacity measurement, a bolotip() function has been defined in the abb.apecs as follow :

be sure to select a valid reference channel

   1 def bolotip(poi=6):
   2         #  Being too cautious
   3         reference(x=0.0,y=0.0,system='ho')
   4         use_spiral ('off')
   5         continuous_data ('off')
   6         use_ref ('off')
   7 
   8         #  move the telescope to zenith to avoid bolometer drifts
   9         source('BOLOTIP-EL88',x=(200.0,'deg'),y=(88.0,'deg'),system='ho')
  10        
  11         # Setting default gain for bolotips and move to the source
  12         abba (dumptime=0.005,gain=1)
  13         laboca (gain=1)
  14         go()
  15 
  16         # Do an sky-hot measurement and the skydip itself
  17         calibrate(mode='hot',time=10)
  18         skydip(am_stop=3.0,points=poi,time=10.0, mode='ras')
  19 
  20         # reset the gain to some default
  21         abba (gain=10)
  22         laboca (gain=4)

please use this macro instead of the skydip() APECS command since, the latter does not take the reference needed to reduce the skydip.

Map

Spirals

OTF

BeamMap

In order to derive the array parameter, a function beammap() has been setup for beammaps :

Do not use this on moving objects or planets, otherwise switch the continuous_data 'off'
These functions cover completely the array if the center channel is set as reference

   1 def beammap():
   2         use_spiral 'off'
   3         continuous_data 'on'
   4 
   5         #OTF 200Hz sampling 2'/sec speed takes about 12min + overhead - > 15min
   6         otf(xlen=720, xstep=0.6, \
   7             ylen=720, ystep=6, \
   8             time=0.005, direction='x',zigzag=1,\
   9             unit='arcsec',system='ho')

Alternatively you can slipt the beammap into 3 smallers maps to ease their reduction

   1 def beammapsplit():
   2         use_spiral ('off')
   3         continuous_data ('on')
   4 
   5         # First centered map
   6         offset(0,0,system='ho')
   7         otf(xlen=780,xstep=0.6,\
   8             ylen=300,ystep=6,\
   9             time=0.005,direction='x',zigzag=1,\
  10             unit='arcsec',system='ho')
  11 
  12         # Second map for the lower part of the array
  13         offset(0,-240,system='ho')
  14         otf(xlen=780,xstep=0.6,\
  15             ylen=300,ystep=6,\
  16             time=0.005,direction='x',zigzag=1,\
  17             unit='arcsec',system='ho')      
  18 
  19         # Third map for the upper part of the array
  20         offset(0,+240,system='ho')
  21         otf(xlen=780,xstep=0.6,\
  22             ylen=300,ystep=6,\
  23             time=0.005,direction='x',zigzag=1,\
  24             unit='arcsec',system='ho')            
  25 
  26         # Do not forget to set back the offsets to default
  27         offset(0,0,system='ho')

Pointing Run

boawiki: Documentation/Observing_Tips (last edited 2009-12-17 15:40:29 by localhost)