Changes between Version 7 and Version 8 of GPC_BrightStarAstrometry_Issue

Timestamp:

Apr 1, 2011, 2:18:53 PM (15 years ago)

Author:

watersc1

Comment:

--

GPC_BrightStarAstrometry_Issue

@@ -39 +39 @@
 || [[Image(o5407g0385o.ota24.dx.png)]] || [[Image(o5407g0385o.ota36.dx.png)]] ||
 
-Checking the differences in positions shows that in the raw cell coordinates, a bright source in GPC1 is at a smaller x position than the 2mass position. This means that an example object in cell00 has been shifted in the direction of cell01. The direction of the shift in cell coordinates is the same on all OTAs. There is some evidence of asymmetry in the raw images as well that supports this shift:
+Checking the differences in positions shows that in the raw cell coordinates, a bright source in GPC1 is at a smaller x position than the 2mass position. This means that an example object in cell00 has been shifted in the direction of cell10. The direction of the shift in cell coordinates is the same on all OTAs. There is some evidence of asymmetry in the raw images as well that supports this shift:
 
 [[Image(asymmetry.png)]]
@@ -49 +49 @@
 == Direction of shift ==
 [[Image(shift.png)]]
+
+The above figure shows cell00 and the full chip mosaic for OTA34 and OTA42 of o5407g0385o.  The full chip mosaic has the WCS overlaid.  I am ignoring DEC, and pretending that RA and x are parallel for simplicity. 
+ * As shown above, OTA34 has RA_IPP - RA_2MASS < 0.  I've scribbled a red arrow on the chip mosaic frame illustrating the direction of this shift.  
+ * Due to the orientation of the OTAs, OTA42 has RA_IPP - RA_2MASS > 0.  I've scribbled a similar red arrow on that frame.  
+ * Comparing to the raw cell00 frames, the shift arrows show that for both OTAs, the IPP measurement is closer to x = 0.  
+ * Returning to the chip mosiac, this direction is towards the adjacent neighbor cell, cell10.