Pointing Origins

The telescope's pointing origin is the physical position within the focal plane corresponding to the currently selected right ascension and declination. Having different pointing origins allows you to specify that a certain object should be placed in the center of the NIRES slit rather than within the field-of-view of the offset guider, for example. The name of the current pointing origin is always displayed in the lower right corner of the Facilities Summary (FACSUM) window. The pointing origin can only be changed by the OA. Below is a list of the current pointing origins (XIM YIM). Last updated: 15-Feb-2019-PG

name	Description	XIM (mm)	YIM (mm)	Xpix	Ypix	Usage
REF	Center of the optical guider	0.1674	-0.0071	512	512	Pointing Check. Pix location on guider detector.
NIRES	Long-slit acquisition	0.00065	0.0016			Longslit acquisition. Target would be close to the slit (depending on flexure). Recommended for faint targets where the observer does not wish the target to be blocked by the slit.
SLIT_IMAG	Long-slit acquisition (off slit)	-0.0069	0.0016			Longslit acquisition. Target would be off the slit by 10" (perpendicular towards the center). Recommended for indentifying targets where the observer does not wish to be blocked by the slit.
REFSLIT	Slit Viewing Camera Pointin Origin	0.00175	0.00077			Pointing Check (for slit-viewing camera) and target acquisition. The target would be on top of the slit (depending on flexure). Not recommended for faint targets.
IMAG	Imaging Pointing Origin	-0.0357	0.00146	?	?	Imaging of a point source. Ensures that the point source does not fall in the quadrant border.
MIRA	MIRA pointing origin	-0.02116	0.02273	?	?	Only used for MIRA.

Note that the Xpix and Ypix depend on flexure between the optical guider and the slit. Therefore, several iterations might be needed to put a target on the slit. Likewise, it is possible that after a slew, the target would land on the slit eventhough one is using the NIRES PO.