The rotary floor was used to test the mapping of motion in the focal
plane to motion on the sky. The setup was:
- lband wide at 1612 MHz was used for the testing. Turret position
is 285.79 degrees.
- The interim correlator was used with 1 second dumps, and 1.2 MHz
bandwidth.
- the corcross routine written for byu was used to do a cross on a
continuum source (+/- 3hpbw, hpbw=3amin) with an offset in az, za
(great circle) included.
- Crosses were done on continuum sources using the offsets in the
table below
Offsets used for tests
turOff
Deg |
scan
|
dx,dy
cm
|
azOff,zaOff
AminGc
|
Notes
AzO -az only offset
GO -Germans offsets
|
0
|
7
|
0,0
|
0,0
|
|
+4
|
9
|
-.45,12.95
|
3,0
|
+
|
+4
|
11
|
-.45,12.95
|
3.25,.24
|
|
+8
|
13
|
-1.81,25.85
|
6,0
|
AzO
|
+8
|
15
|
-1.81,25.85
|
6.61,.98
|
GO
|
+15
|
17
|
-6.33,48.07
|
11.25,0
|
AzO
|
+15
|
19
|
-6.33,48.07
|
13.10, 3.49
|
GO
|
Column descriptions:
- TurOff deg. This is the turret offset from the nominal lbw turret
position of 285.79 degrees.
- Scans: scan number for start of cross
- dx,dy offsets in cm. This is computing by rotating the turret
radius thru the angle specified
- radius of feed at focus: 73.124"*2.54=185.74 cm.
- Positive turret floor rotation moves the feed i +Y (toward the
staircase).
- AOff,zaOff
- These are the az, za offsets used to position the source back
on the feed (at it's offset position). They are the negative of the
feed offset on the sky.
- At each turret offsets, two offsets were tried:
- dAz only: using 45Asecs/turret degrees, dza=0
- German: use german's fits to compute what the az,za offsets
should be for this dx,dy motion.
The plots show t
he results of
the crosses for the turret offsets for 0,4, and 8 degrees (.ps) (
.pdf):
- Page 1: the az, za strips thru the sources
- black is the azimuth strip, red is the za strip. Green is the
2d gaussfit.
- The errors is in arcminutes.
- If the error is negative, the source arrived too early in the
strip, To correct the offset, add the error to the original offset.
- Page 2:
- Top: the x,y feed position in the focal plane for the 3 turret
positions.
- Bottom: The error vs the dy offset
- Black: the azimuth error
- Red : the za Error
- + these used an azimuth offset only
- * these used Germans equations.