Available aperture masks:
 
1 big hole for direct imaging and 2-shuffle
2 matrix for focussing, astrometry, ghost mapping
3 80-shuffle slit for shuffle arcs
4a, 4b, 4c, 4d VPH slits (50um, 100um, 150um, 250um) for grism spectroscopy
5 slot ("fat slit") for time series imaging, polarimetry
6 5-shuffle 5-shuffle imaging, telescope focus, flux standards
7 4-shuffle 4-shuffle imaging
8 3-shuffle 3-shuffle imaging
9 spot automated camera focus
10a, 10b time series, supershuffle for time series imaging, multi-order arcs, plate parallelism