Instrument constraints

        "airmass":                    {"default": "1.6", "max": 5, "min": 1},
        "seeing":                     {"default": "1", "max": 2, "min": 0.2},
        "skyTransparency":            {"default": "Clear", "list": ["Photometric", "Clear", "Variable, thin cirrus", "Variable, thick cirrus"]},
        "waterVapour":                {"default": "30", "max": 30, "min": 0.01}