SUSI2

Sky Brightness

General Values

The following table gives the sky brightness as measured at CTIO (near La Silla) as function of the phase of the Moon. The values are taken from a NOAO newsletter (Walker 1987).

Days from New Moon	Sky brightness [mag/sq.arcsec]
	U	B	V	R	I
0	22.0	22.7	21.8	20.9	19.9
3	21.5	22.4	21.7	20.8	19.9
7	19.9	21.6	21.4	20.6	19.7
10	18.5	20.7	20.7	20.3	19.5
14	17.0	19.5	20.0	19.9	19.2

SUSI2 Sky Values

In the past, the NTT was affected by a problem of scattered light inside the dome, especially during bright Moon. This was greatly improved by painting the inside walls with a high diffusion paint in December 1999.

The sky brightness has been measured on all long (exp.time > 200s) images obtained with SuSI2 after September 2001. The sky was measured using an iterative sigma clipping median estimation. The figures below show the sky brightness as a function of position, and the table lists the median values. These values are in very good agreement with those from CTIO.

V brighness
R brightness

V sky brightness (in adu/2x2pix/s) R sky brightness (in adu/2x2pix/s)

Filter	Median Sky Brightness
	[adu/(2x2bin)pix/sec]	mag/sq.arcsec
V	1.8	21.67
R	2.5	20.63

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Last modified: Thu Nov 06 2003


V sky brightness (in adu/2x2pix/s)	R sky brightness (in adu/2x2pix/s)