SpUpNIC (Spectrograph Upgrade: Newly Improved Cassegrain): A versatile and efficient low- to medium-resolution, long-slit spectrograph on the South African Astronomical Observatory's 1.9-m telescope

We report on the extensively upgraded Cassegrain spectrograph on the South African Astronomical Observatory (SAAO) 1.9-m telescope. The introduction of new collimator and camera optics, a new detector and controller, a rear-of-slit viewing camera to facilitate acquisition, and a new instrument control and quick-look data-reduction software (to take advantage of the entire system now being governed by a programmable logic controller) has revolutionized this workhorse instrument on Africa's second largest optical telescope. The improvement in throughput over the previous incarnation of the spectrograph is ∼50 % in the red, increasing to a factor of four at the blue end. A selection of 10 surface-relief diffraction gratings is available to users, offering a variety of wavelength ranges and resolutions, with resolving powers between ∼500 and 6500. SpUpNIC (Spectrograph Upgrade: Newly Improved Cassegrain) has been scheduled for ∼80 % of the time available on the 1.9-m since being installed on the telescope in late October 2015, providing the single-object spectroscopic capability to support the broad research interests of the SAAO's local and international user community. We present an assortment of data obtained for various observing programs to demonstrate different aspects of the instrument's enhanced performance following this comprehensive upgrade.