Changes

* SpUpNIC suffered severe grating instability problems which have been that were incrementally reduced through various interventions, the last of which was the introduction (in early November 2016) of a pneumatically-actuated lock to clamp the grating mechanism at the user-defined angle. The lock is under software control and can thus be de-activated by the user in order to adjust the grating. We are delighted to report that the lock has eliminated the last of the play within the grating mechanism! Flexure remains a sad reality inevitable for a Cassegrain spectrgraphs though spectrgraph as they swing it swings about the sky on the backs back of telescopesthe telescope. Thus Therefore we still recommend that users bracket their target observations with arcs (taken immediately before and after the object exposures) so as to calibrate out any remaining shifts due to flexure.

* The angles listed in the second last column of the table below will get one into the range where lines are visible for a given grating, then adjust the grating angle to obtain the desired wavelength range - consult the arc maps sample arcs in the right-hand column of the table, or see and the ones in the old spectrograph user manual (a hard copy is available in the warm room)arc maps linked to below.

* Click on the following link links for arc maps for <big>'''[[Sample Spectra of Spectrophotometric Standard StarsG4]]'''</big> observed with G4, <big>'''[[G5, G6 ]]'''</big> and <big>'''[[G7]]'''</big>. Arc maps for the remaining gratings will be posted once they are available.

* Click on the following links for arc maps link for <big>'''[[G4Sample Spectra of Spectrophotometric Standard Stars]]'''</big>observed with G4, <big>'''[[G5]]'''</big> , G6 and <big>'''[[G7]]'''</big>.