What we know about pointing etc.

19Aug04 notes

1. There were cross scans done, but since the positions in the headers
   were wrong, they have not been analyzed for pointing. There has not
   been a complete pointing model made for ALFA as of yet.

2. The main pointing models are constructed via detailed pointing tests
   using the S-band feed. The other feeds are then pointed with respect
   to this model.

3. The pointing for ALFA so far showed a 50" offset with respect to the
   S-band model for beam0. The origin of the offset is not known though
   it is within the expected offset.

4. There have been no tests done with the array rotated, nor have there been
   any tests done to verify that the axis of rotation coincides with beam0

5. Desh states that beam0 has a pointing accuracy of about 10" in each
   coordinate at PA=0.

6. Offsets are available for the outer beams based on the model; they have
   been verified by manually peaking up on sources. The offset values (from Desh) 
   in arcsec, for PA=0, are:
      beam          azOff    zaOff
       0             0.0      0.0
       1          -164.53   332.558      
       2          -329.06     0.0 
       3          -164.53  -332.558
       4           164.53  -332.558
       5           329.06     0.0
       6           164.53   332.558
   Note that these offsets are fixed in az,el (not ra,dec)
   and this makes life interesting. See Phil's web page on the beam config.

7. Desh states that we should be able to process the cross scans using
   Tapasi's IDL routines. (However, they don't work at the moment.)