Hubble Space Telescope
Sky Rough Estimate

This option merely selects between "average" sky background conditions, and "high" and "low conditions.

Values assumed are:

Low = 23.3 V mag arcsec^-2 which represents minimum zodiacal light for sources at high ecliptic latitudes.

Average = 22.5 V mag arcsec^-2 which represents average zodiacal light.

High = 21.0 V mag arcsec^-2 which represents maximum zodiacal light + reflected earth light.