[evlatests] Some Nice Imaging Results

[Rick Perley]

    The 7-hour antenna gain measurement observation made Friday (or 
which much has already been written ...), has provided a nice test of 
whether there are any significant issues with imaging at the various 
bands.  The source observed -- 3C345 -- has about the same flux at every 
band, and is strongly dominated by a central point source at every band. 

    For each band, after flagging etc., there remained about 40 seconds 
of good data for each of the 37 individual observations -- spanning 
about 6.5 hours.  A total of about 25 minutes on-source integration, per 
band. 

    After delay, bandpass, and gain calibration, I extracted a 
50-MHz-wide 'pseudo-continuum' database for each frequency.  Self-cal 
was used (amp&phase) for each record (averaging time 1 second), starting 
with a 10 Jy point source.   Subsequent cycles used the derived image.  
A few wayward points (almost none) were clipped away.  BLCAL was used if 
there was sign of closure errors (significant only at the low 
frequencies), and images made. 

    All images are quite lovely, and appear thermal-noise limited, 
except perhaps at the two lowest bands. 
    Here is a short table showing the rms noise in each field.  The peak 
on each map is 10 Jy. 

    1444 MHz   0.16 mJy
    1819            0.14
    2560            0.23  (18 antennas)
    3520            0.11  (19 antennas)
    4440            0.063
    6690            0.057
    8300            0.062
    11299          0.15  (13 antennas)
    13140          0.11  (16 antennas)
    16740          0.12  (16 antennas)
    19500          0.11
    25550          0.12
    29500          0.19
    36500          0.25
    42000          0.47
    48000          1.0 mJy