Observing Block execution

One specific issue under discussion is the seeing requirements provided for the execution of fast-track proposal observations. Currently, one can choose to have a maximum limit of 0.7, 1.0, 1.3, or `no limit' on the seeing. However, these limits are not specifically related to the distribution of the observed seeing at the observatory, and it is not specifically clear at what wavelength or zenith distance this is defined. As a first step, and as also generally used, the seeing has now been defined at a given airmass (1.0) and wavelength (500 nm). The plan is to review the observed seeing (which could either be the DIMM statistics, or as derived from our own [ALFOSC] measurements), and define limits at (e.g.) the 10, 50 and 90 percentile limits. Here, we also are considering to add an additional high limit option (e.g., 2.0 arcsec) apart from no-limit, up to which still reasonable observations can be made for bright targets, but above which any practical observations are in general not possible (e.g., because stars in the field of view can no longer be separated). As part of this more specific definition, an application will be made that provides the corresponding seeing at a given airmass/zenith distance and wavelength/pass-band for a given seeing. This both should clarify to proposers what the given seeing (and airmass limit) implies for the wavelength/pass-band they select, and for the (service) observer to assess if the observations comply with the provided seeing requirement.