Setting the Grating Angle

There are three methods for setting the grating angle using the XLRIS GUI.
• Angle: sets the grating tilt
• Wavelength: sets the central wavelength assuming the long slit will be used to acquire a spectra
• MSWavelength:sets the central wavelength for a slit located in the center of the mask.

The Wavelength and MSWavelength fields may be used to set the grating angle. Based on the desired wavelength and the current grating, the angle is calculated and then set by the software. The XLRIS GUI will update the grating angle after the mechanism has stopped moving.

Note that from run to run, the angle, wavelength, and mswavelength may vary from previous setups. Each run you will need to fine tune your angle or wavelength setting to acheive the wavelength coverage necessary to fullfil your science requirements. Each grating port has a different offset. The offsets between positions may result in wavelength differences of order a few 100 angstroms. In extreem cases, a thousand Angstrom shift may be necessary to acheive a wavelngth range defined during a previous run.