• Obtain the sky brightness in optical B, V, and R photometric bands above Dome A site

• To measure the cloud cover extent during the 2009 and 2010 winter seasons• Extended to 2011 by NSF

• To provide aurora and airglow statistics

• Photometry of bright target stars in field with unprecedented window function

$ Meet budget of ~$50k (NSF OPP/AST award) excluding logistical costs• All logistical costs provided by

PRIC/China collaboration

Gattini-DomeAGoals of experiment

• 90o FoV transit camera + Optic ‘IFW’ filter wheel (B, V, R, >650nm)

• Apogee Alta ‘U4000’ 2kx2k interline CCD with 7.4 micron pixels

• AF DX Fisheye-Nikkor 10.5mm f/2.8G ED results in ~2.4arcmin/pix,

aperture ~few mm

• Continuous observations:– 100s B 30s B– 100s V 30s V– 100s R 30s R– 100s OH 30s OH– 100s dark– BIAS frame– REPEAT

Camera, Data

V sky brightness, whole season

• CAUTION: more work needed to assess effect of imperfect baffling (are we measuring true sky brightness or instrument performance?)

Photometry

• Strongly suspect “cloud” equals local snow obscuration lifted by wind in many cases

‘Cloud’ cover