The slit nod widget is used to fine tune object positions on the NIRSPEC slit. It can also be used to manually nod objects along the slit. The widget starts automatically when the NIRSPEC instrument software starts up. The widget can also be launched indepedently from the NIRSPEC Menu -> NIRSPEC GUIs menu -> Slitmove Gui.

The images below describe the direction the object will move with a positive offset in the widget, for low resolution mode and for high resolution mode. Offset values can be in units of arcsec or pixels by clicking the appropriate radio button. Offsets can be applied either along the slit by clicking Nod Along Slit, or perpendicular to it by clicking Nod Perp Slit, or both simultaneously by clicking Nod Both Directions.




Low resolution slits:



High resolution slits:


Command-Line Slit Nodding:

If the user prefers to do slit nodding with typed commands, he or she can simply type in a window with a waimea prompt:

slitmove [along] [perp]

where the values of [along] and [perp] are always in arcsec; the plate scale of the SCAM is 0.158 arcsec/pixel. So for example to nod perpendicular to the slit by -0.5 arcseconds, the command would be:

slitmove 0 -0.5