Tests were made with a vertical slit. This showed much better read-out times for windowing, down to 5 sec for a window that allows background subtraction, compared to about 25 sec in vertical mode). However, tests are needed to find out how repeatable the slit wheel positioning is, as this is more critical for the vertical slits as they are positioned radially with respect to the wheel. Also, we would need better slits for regular observations.
For half of the available grisms the efficiency was measured. In Table 3 the total peak efficiency of the telescope plus ALFOSC plus detector for the different grisms are given as measured with a wide slit.
| Grism | Efficiency (%) |
| # 3 | 22% |
| # 4 | 28% |
| # 6 | 22% |
| # 7 | 26% |
| # 8 | 23% |
| # 10 | 25% |
| # 11 | 30% |
| # 12 | 26% |
Tables with S/N versus magnitude for a given exposure time will be provided on the web to assist writing proposals.