- go to the ''Advanced'' tab on the control GUI and click the ''grating angle initialise'' button (in the bank of buttons on the left)
* Once you have the correct grating in the spectrograph, enter the approximate starting angle (given in the grating table above) in the ''Grating angle'' box and click ''Go''. Compare the resulting * Take an arc and check the wavelength range on the Quick-Look extraction that will appear shortly after the image is read out. * If the spectrum with is too blue (red), decrease (increase) the grating angle and repeat the arc maps shown in to check the table abovenew wavelength range - iterate until happy with the range. * Note that angle changes <0.05 degrees are too small, or in Chapter 10 so make a larger change and then go back the other way to achieve very small shifts (the software takes care of backlash in the system by ensuring that the desired value is always approached from the old spectrograph manualappropriate direction).
* The software knows which order-blocking filters should be used with each grating, but it is still a good idea to check that the correct filter is selected (refer to the table above). If necessary, select the required filter from the drop-down menu at the bottom of the ''Instrument Setup'' pane and click ''Go''.