Sky brightness variation
Variation of measured sky brightness in: Z (lightblue), Y (black), NB118 (purple), J (blue), H (green), Ks (red), passbands over the period 20th May 2009 to 23rd June 2009 (see summary QC pages ..... for further details of individual nights).
Sky Brightness as a function of sunset/sunrise time
The following plots show the variation of sky brightness after sunset and before sunrise. All photometric nights have been used to make those plots, i.e. no constrains on moon phase or position although all observations are done at a distance of 30 degrees or more away from the moon.The dashed lines indicate the astronomical twilight. It is clear that Z, Y, NB1180 and J bands suffer from the effect of the excitation of the OH lines until after 1.5 to 2 hours after twilight. The brightness of the sky remains constant after the morning twilight as expected.>