FOV, spectroscopic format, and AG vignetting on CCD

Overview

Please plan the target acquisition that takes a full advantage of the FOV in FOCAS. 

Note:

Imag: 6 arcmin fai + 5 arcsec gap at center (between chips)
Spec: Long slit gap at center of each chip


Chip orientation on sky at various PA of telescope


       PA=0           PA=90           PA=180          PA=270

    ____N____       ____N____       ____N____       ____N____
   | chip#2  |     |    |    |     |   #1    |     |    |    |
  E|_________|W   E| #2 | #1 |W   E|_________|W   E| #1 | #2 |W
   |         |     |    |    |     |         |     |    |    |
   |_chip#1__|     |____|____|     |___#2____|     |____|____|
        S               S               S               S

                       ^red
     ------> red       |          red <------           |
     lambda            |                                |
                                                        V red

How to apply pointing coordinates

Imag: Spec: In order to avoid the gap between the chips when inserting an object, you need:

1.  Object coordinates
2.  Distance (offset) measured towards chip1 from the center of view (not counting Instrumental PA).

   It is not necessary to calculate the coordinates for offset position if the offset is already given. 

        Spec: It is not necessary to calculate the coordinates for offset position since the conversion between center slit and offset slit would be done by the option in the pointing abstract command.

Spectral Format on CCD

Notes:

The vertical pix is opposite in sign from the actual Y coordinate on CCD. 
It is for coinciding all the slits at the center.

Measured WCS for spectroscopy

Wavelengths on CCD <-> Empirical value matching the pixel 

Notes:

All data are taken with 2 bin mode in wavelength.
Negative dispersion means increasing wavelength as decreasing CCD Y pixel.
These values are for before the distortion correction.