[evlatests] Nothing but noise!

[Bryan Butler]

this is the famed yin-yang mode?


On 5/30/07 14:31, Rick Perley wrote:
>     I used 4.5 hours of free 'Dynamic Time' last night to do a deep 
> integration at L-band on a random background field. 
> 
>     Setup:     BW = 12.5 MHz.  Mode = '4'.  This gives 16 channels, each 
> of 781 kHz, for each of the four parallel hand correlations.   
> Integration time was set to 3.33 seconds. 
>     Calibration:  I observed 3C286 once every 15 minutes, for one minute. 
> 
>     Bandpass solutions (with Hanning smoothing on, to reduce the Gibb's 
> oscillations) were done for every calibrator observation. 
> 
>     Straightforward gain calibration (2-point) was then done.  The usual 
> flagging was done to remove bad antennas and visibilites.  In general, 
> the data were of excellent quality.  27 antennas worked (but not all of 
> them well). 
> 
>     The randomly chosen field was at:  RA = 13 30 00, Dec = 28 00 00.  
> (The strong sources 3C286 and 3C287 were each about 2.5 degrees away).  
> Afterwards, I checked the NVSS map archive, to find that I had put the 
> beam in a remarkable 'hole' -- virtually no sources within the primary 
> beam!  (I checked because my first image returned rather fewer sources 
> than I expected to see!) 
> 
>     Imaging Results:
> 
>     I made many images, with single channels, and blocks of channels, 
> with one IF and both IFs,  of selected fields, and of the whole primary 
> beam (this takes a long time -- my machine is still laboring away ...).  
> But one result is very clear: 
> 
>     *********  There are no artifacts of any kind, at any place, in any 
> channel, in any images  ********
> 
>     The full-beam, both-IF, 13 channel (channels 2 through 14) image is 
> showing dozens of sources at the few-mJy level (and less), with rms 
> noise levels below 100 microJy.  The sources are clean and sharp.  Tests 
> with EVLA only and VLA only subsets show the same sky, with noise levels 
> more or less in inverse proportion to the number of antennas available. 
> 
>     All looks completely normal to me. 
> 
>     Specific EVLA problems (and there are a few!) will be described in a 
> subsequent report.
> 
> 
>    
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