Photometry of WZ Sge at RIT Observatory: August 12, 2001 UT

On the night of August 12, 2001 UT, 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:

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 8.8 arcseconds.

The night started out clear, but clouds rolled in several hours after sunset. They cut the observing run short, so that good data was acquired only from Aug 12.04 UT to Aug 12.14 UT.

We gathered 434 images of the field, but discarded many due to the clouds. We fed all raw instrumental magnitudes of 115 stars on 400 images into a program which implemented Honeycutt's inhomogeneous ensemble photometry technique. The solution gave most weight to the bright stars "A" and "B" (marked 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 and "B" = HD 351517 as follows:

       star   mean      stdev
         A    0.0       0.003
         B    0.983     0.007 

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. We also discarded all data taken after JD *133.635, as it was clearly of poor quality.

The final result is 341 measurements of WZ Sge over a span of two and a half hours. Here is the light curve:

You can download an ASCII text file with the measurements:

• download WZ Sge data

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 

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 8/22/2001 by MWR.