• Naming conventions:
  
• FieldX
  
• X=1..4 individual fields
• X=All .. 4 fields mosaiced together.
• 3C234 - beam map
  
• G11 -> 11arcmin gaussian used for gridding of individual fields.
• _AVG.FITS  . Pol A, polB averaged
• _PolAAVG.FITS  .. made with only polA.
  

Intro
The steps in processing the data
Map positions raw data
    Plot: sampled map positions for each field (.ps) (.pdf).
    Plot: where all 4 fields fit into the final combined map (.ps) (.pdf).

Removing Tsys.

The individual maps by field
    The  average maps for each field (.gif)

Mosaicing the 4 fields together

Intro: (top)

    Data was taken feb,mar 2017

 

mapname	map center ra, dec
Field1	09:46:47.5, 25:54:59.9
Field2	09:26:48.5, 24:54:59.9
Field3	09:47:13.2, 30:24:59.9
Field4	09:26:22.8, 30:24:59.9
3C234	10:01:49,28:47:09

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The steps in processing the data  (top)

• see a2125 steps in making the maps.
• PolB showed some jumps in Tsys (probably the jennings relay)..
• maps were made of the  PolA + polB and just polA.
  
• The beam map was processed separately
  

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Map positions   (top)

• Pages 1shows the az,za positions for each field
• Page 2 has the ra/dec sampled positions for each field (labels are not very helpful).

• each field is plotted in a different color.
• an index (0..3) is plotted on top of each field for identification
• The list at the bottom of the plot, maps index number of field name, and average ra, dec for each field
  

Removing Tsys (top)

• Create a model of the za dependence of Tsys using the x102 data (tsysX102M). Normalize this so tsysX102M(za=10) is 1.
• For each map (ra,dec strips processed together):
• fit for the scale factor TsysData(za)=tsysX102M(za)*scale
• TsysRemoved= TsysData(za) - tsysX102M(za)*scale  .. this is done separately for pola, polb.
• If the actual Tsys changes over time ,this should help correct for that.
• If the cal Values change (without remeasuring them), then the 0 of tsysRemoved should be ok, but the scaleFactor of tsysRemoved will still be off (since we didn't scale it by the change in the cal values).
  

• Plot (TsysA/TsysB -1) before fitting or corrections (.ps)
• The data has been converted from correlator counts to kelvins using the cals (after cal fitting).
  
• Top: TsysA/TsysB-1 vs za
• 2nd: TsysA/TsysB -1  vs az
• bottom:TsysA/TsysB -1 by field
  
• dashed green lines separate fields.
• The large spread is from polA varying.
  
• It looked to be stable for a days run.
• My guess is the jennings relay (load,antenna switch) is probably making different contact whenever the 430 was switched to load (during testing).
  
• Cal scale factors by field (.ps)
• These values are computed from the cals on every strip. they convert from correlator counts to Kelvins.
  
• black (polA) ,red(polB) after cal fitting
• green(polA), blue(polB) before cal fitting
• Cal fitting takes adjacent cals (with no attenuation changes) and does a linear fit to the measured scaling factor ( throwing out outliers). The fit is then used to convert correlator counts to kelvins rather than the individual measurements.
  
• If there are no outliers than the blue,green overlay the black, red traces.
  

• Global fitting of all the data:
• Plot Tsys vs za and then fit for all data at once (.ps) 
• Show fit residuals by field (.ps)  
• Fitting Tsys by Field.
•  Remove tsys by field (rascans, decscans separate). plot Residuals for each field (.ps)  
• Each page is a separate field.
  
• top: polA, bottom PolB
• Black points are the rascans, red points are the dec strips
• When the images are made, Tsys is removed from the ra and dec scans simultaneously
  
• We left them separate here to see if the ra, or dec scans had any outliers.
• Tsys residuals by field (rascans and decscans together)(.ps) 
• Same as above plots but the scaling fit is done with ra and dec strips together. This is how the images are made.
• Black is polA, red is polB.
  
• The scale factor and errors are included in the title for each plot.

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The individual maps.  (top)

1. grid the ra driven and dec driven maps separately to the same grid.
• Grid spacing was 3 arcminutes.
• The gridding function used a gaussian with a fwhm of 11 amin.
• A sin projection was used to project onto the  2-d grid.
2. basketweave the two  maps. Create an average map and a difference map after basketweaving.
• The basket weaving will try an remove offsets in strips.

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Mosaicing the fields.  (top)

1. take each pair of overlapping maps.
   
2. Interpolate the first map of each  pair to the grid position of the second  (within the overlap region).
3. compute  mapRaDif=(map2 - interpolated Map1) in the overlap region
4. Fit a linear polynomial to the differences as a function of the ra position
5. Correct the two maps by subtracting half the difference from map2 and adding half the difference to map 1
6. Repeat steps 1 5 with the corrected fields, using the dec overlap of the pairwise maps.
7. 21feb11: changed so that 1-6 only corrects 20% of the difference. It then iterates 1-6 5 times. This gets rid of jumps caused by the correction.
   

• the units are Janskies (multiply by 10 to get kelvins).
  
• Top 2 frames:  Overlap in ra direction with  map1-map2Interpolated plotted  vs ra.
• The red line is the fit  vs ra.
• Bottom 2 frames: Overlap in dec direction with map1 - map2Interpolated plotted vs dec.
• Each set is the start of iteration i (i=1 to 5). the last one is when everything is done. The set shows how the correction progresses with a correction factor of 20% per iteration.
• Pairwise difference overlap region:Iteration 1 start (.ps) (.pdf)
  
• Pairwise difference overlap region:Iteration 2 start (.ps) (.pdf)
  
• Pairwise difference overlap region:Iteration 3 start (.ps) (.pdf)
  
• Pairwise difference overlap region:Iteration 4 start (.ps) (.pdf)
  
• Pairwise difference overlap region:Iteration 5 start (.ps) (.pdf)
  
• Pairwise difference overlap region:Iteration 5 end (.ps) (.pdf)
  

The final mosaiced maps (.gif):

• The  x,y positions are just grid points along the ra,dec direction.
  
• This used a 5.5 arcmin gridding function. The final resolution is about 14 arcminutes.
Processing: combinemaps.pro

Notes on the fields.  (top)

• PolB tsys was changing run to run. My guess is that the load switch (jennings relay) was being moved between runs, and the  switch was occasionally making poor contact