The effect of solar activity on the V and B band sky brightness

Abstract

Measures at San Benito Mountain during the period from 1976-87 show that the zenith sky brightness in the V and B photometric bands is well correlated with the solar 10.7-cm radio flux, and thus with the intensity of the solar EUV radiation in the 100 A-625 A range. A change of at least AV = 1.0, AB = 0.8 mag may occur as the EUV intensity varies with solar activity. In addition, the brightness of the zenith sky is found to decrease exponentially by about 0.4 mag in both V and B during at least the first half of the night.These results indicate that:(1) The level of solar EUV flux and the time of night must be taken into account when assessing the quality of a dark-sky site.(2) In order to obtain the best signal-to-noise ratio for limiting observations in the V and B filter bands, it is of importance to observe at times of minimum solar EUV radiation and in the latter part of the night.(3) Nighttime sky brightness may be predictable with reasonable accuracy from the intensity of the 10.7-cm radio flux observed during the preceding day.

A robust algorithm for sky background computation in CCD images

“…With this exposure time, a seeing of 1 and the typical FORS1 zero point in the V passband (m 0 28), Eq. (18) gives m f ∼ 22.8, which is about 10 magnitudes fainter than the value for typical photoelectric sky brightness surveys (Walker 1988). Such faint objects contribute to less than 1% to the total brightness (Roach & Gordon 1973) and therefore we can conclude that our method is practically free from being biased by the inclusion of faint foreground point sources.…”

“…For these reasons, the data are usually rather scanty and suffer from the inclusion of bright stars (V ≥ 13; see for example Walker 1988).…”

Airglow and Aurorae from Dome A, Antarctica

“…Airglow varies on both short and long timescales: atmospheric gravity waves are responsible for fluctuations on timescales of minutes (e.g., Li et al 2011); solar tides produce diurnal (e.g., Brenton & Silverman 1970;Fukuyama 1976) and semiannual (e.g., Deutsch & Hernandez 2003) oscillations; and the solar cycle causes decade-scale variations, with sky brightness typically being 0.4 mag brighter during solar maximum (Krisciunas 1997;Patat 2008), with the 10.7 cm solar radio flux commonly used to measure the level of solar activity (e.g., Walker 1988). Temporal fluctuations also display a complex dependence on geographic latitude (e.g., Forsyth & Wraight 1987).…”

The artificial night sky brightness mapped from DMSP satellite Operational Linescan System measurements

“…In lack of measurements of natural sky brightness in Europe at sea level, we assumed it at minimum solar activity B = 22.7 mag arcsec −1 in B band, and V = 21.6 mag arcsec −1 in V band, estimating an incertitude of at least ±0.1 mag arcsec −1 . Natural sky brightness increases when solar activity increases (Walker 1988) and the solar activity in 1998 was close to minimum but not at the minimum, so it could be underestimated and consequently the artificial brightness in darker sites considerably overestimated. The sky brightness has been transformed into photon radiance with formulae of Garstang (1989a: eq.…”