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Session 41 - Visible & UV Telescopes.
Display session, Thursday, January 08
Exhibit Hall,
One mission of the Center for Astrophysical Research in Antarctica is to determine the benefits of establishing observatories at the South Pole. We have shown that the South Pole sky is extremely dark in the thermal portion of the K\/ band (called K_dark, 2.27-2.43 \micron), exhibiting average sky brightness of 16.7 mag arcsec^-2 \quad (Nguyen et al. 1996). Because the South Pole experiences weather not found at most observatories, like airborne ice crystals, we needed to determine if it is ever photometric.
This past austral winter we made observations to characterize the near-infrared extinction and its variation over 8-hours. Our procedure typically consisted in measuring the brightness of 10 standard stars which spanned a range of magnitude (K \sim 7-12) and airmass (sec(z) \sim 1-2.5). Our program included measuring the extinction 2 or more times in 8 hours at least 3 days per month from May through August. We also measured the extinction once on another 5 days in each month. In order to characterize the hourly variation of the transparency, in mid-July we spent 6 days monitoring 3 standard stars.
After a preliminary analysis of the observations, we draw the following conclusions.
1) The South Pole shows good to excellent K\/ band transparency with most observing days having extinction of 0.12 mag airmass^-1 \quad or better.
2) Days with good extinction show good to excellent stability over 8 hours with an average change of 0.1 magnitudes. Days with poor to fair extinction show greater variation.
Nguyen et al. 1996, PASP\/ 108, 718
The National Science Foundation supports this research through Grant No. NSF DDP 89-20223.
