Photometry of WZ Sge at RIT Observatory: September 04, 2001 UT

On the night of September 04, 2001 UT, Brad Conrad and Michael Richmond used the RIT Observatory's 10-inch Meade LX200 telescope to monitor WZ Sge. All exposures were taken without the focal reducer, through a V-band filter, onto an SBIG ST-8 CCD camera. Each exposure was 10 seconds long. Due to the design of the SBIG software, the time of each exposure is accurate only to +/- 1 second. The field of view was about 17 by 12 arcminutes, a typical example is shown below (North is up, East to the left):

We subtracted dark current from the images and divided by a median twilight sky flatfield. We ran software to detect all stars more than 4 sigma above the sky, then measured the light from each star within a circular aperture of radius 6.6 arcseconds.

The night was not good: although clear at the start, thin high clouds soon swept over the sky, becoming thicker with time. We gave up after about 2.4 hours.

We gathered about 350 images of the field. We fed all raw instrumental magnitudes of 101 stars into a program which implemented Honeycutt's inhomogeneous ensemble photometry technique. The solution gave most weight to the stars marked "A" and "B" in the chart above. The standard deviation from the mean magnitudes in the solution are shown below, as a function of differential magnitude.

The solution placed the mean magnitude of stars "A" = GSC 1612.1830 = HD 191083 = Henden's "C", "B" = Henden's "A" = GSC 1621-0989, and "D" = Henden's "CS" = GSC 1621-1758 as follows: 

       star   mean      stdev
         A    0.0       0.004   
         B    0.978     0.007
         D    3.046     0.023

We used star "B" as a check star to detect errors due to clouds or poor images (which clearly were present in the entire night's run). We discarded any image in which star "B" differed from its mean magnitude by more than +/- 3 times its standard deviation.

The final result is 344 measurements of WZ Sge, over a period of 2.4 hours. Here is the light curve:

You can download an ASCII text file with the measurements:

The file has some comments at the top, followed by data lines with 4 numbers per line, like this: 

        Jul_27.06510     2117.56510   2117.56977   0.046
The columns are:
  1. UT day
  2. Julian Date - 2,450,000
  3. Heliocentric Julian Date - 2,450,000
  4. differential V-band magnitude of WZ Sge (relative to star "A" = HD 191083).

Last modified 9/04/2001 by MWR.