NOTcam spectroscopy: how to align slits

NOTcam currently has a small rotational offset between sky angles and detector columns and rows. For a given telescope rotator angle, the actual angle on the detector will be slightly different.

For NIR spectroscopy this has a consequence when nodding along the slit: the slit should be aligned such that telescope nods along the slit do not move the star off the slit in the perpendicular direction.

Ideally the TCS should account for rotational offsets between instruments and sky. Currently it does not have this ability.

The actual rotational offset should be determined on-sky after each opening/closing of NOTcam. Slit alignment should be checked subsequently.

Instructions for aligning slits:

NOTcam spectroscopy: how to focus slits

Currently the 128 micron slit and the 64 micron slit are displaced by approx 5mm (both towards the camera). The 64 micron slit needs camera focus settings which are about 150 units lower than that of the 128 micron slit (see table). The 44 micron slit is displaced away from the camera, in order to be able to focus it in HRC-mode.

Note that with the grism in the beam the internal focus for the WFC should be upped by 200 units. (Still needs to be checked for HRC mode!)

Instructions for focusing WFC:

Instructions for focusing HRC:

John Telting (jht)