This is a very important magnitude to determine the threshold of detectability in near-infrared wavelengths. Sky brightness can be determine as follows:
SKYB = ZP - 2.5log(SK/scale2)
where ZP is the Zero Point, SK are the counts/sec/pixel2 from the sky and scale is the angular scale at the detector = 0.3961"/px. The sky brightness is measured in magnitudes per arcsec2.
| date | filter | sky brightness (mag./arcsec2) |
mean SKYB (mag./arcsec2) |
|---|---|---|---|
| 11th Feb. 2001 (bright night) | J | 15.459 | 15.57 |
| 15.446 | |||
| 15.813 | |||
| Km | 12.198 | 12.18 | |
| 12.078 | |||
| 12.273 | |||
| 12th Feb. 2001 (bright night) | J | 15.218 | 15.50 |
| 15.479 | |||
| 15.793 | |||
| Km | 12.122 | 12.16 | |
| 12.130 | |||
| 12.240 |
We have a sky brightness of 15.54 mag./arcsec2 in J-band and 12.17 mag./arcsec2 in Km-band on February 2001.