ASAS April 1997 observing run on Las Campanas

The prototype camera system was succesfully shipped to Las Campanas Observatory on March 15, and was assembled and tested on April 3-6. The first light on LCO was obtained on April 4, and the first almost routine observations were started on April 7. Since than the prototype camera was taking data in the supervised mode on each of the next 18 nights. The prototype was left on Las Campanas running and now takes data on each clear night in the fully automated mode. The prototype is located near the Polish 1.3 m telescope and resident astronomers from the OGLE team took care about closing the instrument in case of rain or snow.

ASAS Selected Regions

About 20 2deg x 3 deg fields were selected on the southern sky for the first run. They cover approx. 120 sq. deg and are located in variety of places, ranging from quite "empty" South Pole (Octans) field to pretty dense areas in the Milky Way (Centaurus). One field in Virgo was selected to test software capabilities to discriminate between stars and galaxies. Here is the comlete list of the ASAS Selected regions:

Field Name    R.A.     DEC

    NVEL1999   10:44:49  -52:25:35
   GRB980923    5:07:48  -80:36:00
       LMC_1    5:10:00  -68:10:00
       LMC_2    5:10:00  -70:00:00
       LMC_3    5:40:00  -68:10:00
       LMC_4    5:40:00  -70:00:00
 Centaurus_1   11:35:00  -60:00:00
 Centaurus_2   11:35:00  -61:50:00
 Centaurus_3   11:35:00  -63:40:00
    Octans_1   12:00:00  -85:00:00
       Virgo   12:30:00    3:00:00
   Coal_Sack   12:50:00  -63:00:00
  PG1323-086   13:25:00   -8:50:50
 Centaurus_4   13:50:00  -30:00:00
 Centaurus_5   13:50:00  -31:50:00
       Libra   15:05:00  -15:00:00
 Sagittari_1   17:00:00  -22:30:00
     Scorpio   17:55:00  -35:00:00
 Sagittari_2   18:00:00  -23:30:00
 Sagittari_3   19:00:00  -22:30:00
    Corona_A   19:00:00  -40:00:00
 Sagittari_4   20:00:00  -20:30:00
 Capricorn_1   21:00:00  -17:00:00
 Capricorn_2   22:00:00  -12:00:00
    Aquarius   23:00:00   -6:30:00
      Pisces    0:00:00    0:00:00
       S-092    0:55:00    1:00:00
       S-093    1:55:00    0:45:00
       S-094    2:56:00    0:30:00
       S-095    3:53:00    0:00:00
       S-096    4:52:00    0:00:00
       S-097    5:57:00    0:00:00
       S-098    6:51:00   -0:20:00
       S-099    7:56:00   -0:20:00
       S-100    8:53:00   -0:40:00
       S-101    9:57:00   -0:30:00
       S-102   10:57:00   -0:20:00
       S-103   11:56:00   -0:30:00
       S-104   12:43:00   -0:30:00
       S-105   13:37:00   -0:20:00
       S-106   14:40:00   -0:10:00
       S-107   15:40:00   -0:20:00
       S-108   16:37:00    0:20:00
       S-109   17:45:00    0:00:00
       S-110   18:41:00    0:10:00
       S-111   19:38:00    0:10:00
       S-112   20:42:30    0:10:00
       S-113   21:41:00   -0:20:00
       S-114   22:40:00    1:00:00
       S-115   23:40:00    1:00:00

Some preliminary results

Standard dark frame subtraction and flatfielding was automaticaly done for each frame. Than the customized software for the object detection, classification and aperture photometry was run on each frame. We did not used profile photometry because of the current problems with the PSF shape. Star density varies between 1000 and 8000 stars per frame, at about 4-sigma detection thresold. Aperture photometry seems to be acurrate (in the crowded field) to within 0.01 mag for the brightest (not yet saturated) stars.

Presented data show Centaurus_1 Region, crowded field in the Milky Way. Current data set covers 8 nights (April 7-14) and consists of over 80 images. Each frame contains more than 6000 stars above 4-sigma thresold. There are few saturated stars as well as few bright unresolved blends in the image. The brightest star (1/5 from bottom 4/10 from left) is SAO....

The following magnitude vs. magnitude dispersion diagram presents intrinsic variation of the stars' aperture photometry as a function of the star brightness. Solid line delimiters "variable candidates"; their corresponding "light variation" curves are shown below.

Picture below shows "constant stars" - for which star brightness disspersion is smaller than average:

Next picture shows "variable stars" - for which star brightness disspersion is much larger than average (it is obvious, that for a while many "variables" are due to individual outstanding points, probably missidentifications):

Stars brighter than magnitude 7 are may contain saturated pixels and therefore their magnitudes are only approximate.

Grzegorz Pojmanski / gp@sirius.astrouw.edu.pl