On Jul 18, 2003, EDT, I used the 12-inch Meade LX-200 to measure the variable star V603 Aql.
Notes from the night
Here's a chart of the field of V603 Aql, taken with our equipment: the field is about 16 arcminutes wide.
I measured the instrumental magnitude of each star with aperture photometry, using a radius of 6 pixels = 11.2 arcseconds, and sky defined by an annulus around each star. Following the procedures outlined by Kent Honeycutt's article on inhomogeneous ensemble photometry, I used all stars available in each image to define a reference frame, and measured each star against this frame.
Below is a graph of the scatter in differential magnitude versus magnitude. Note that star "A" is saturated. I did not include it in the solution as a reference. I also removed star "B" from the ensemble reference set, since I suspect it is close enough to saturated to be unreliable as a comparison.
The outlier at differential mag = 3.3 is V603 Aql.
It is clear that most of the stars in the field are not varying appreciably, but V603 Aql is, as the green light curve shows The other data belong to stars B, C, E and F, and P.
After making the ensemble solution, I looked at the values for star "C". If its magnitude in one particular image lay more than 3 standard deviations from its mean magnitude, I declared the image BAD and discarded it from all subsequent analysis. There was 1 "BAD" out of 419 images.
Here's a closeup of the variation in V603 Aql itself:
I've modified the way I report the differential magnitudes. I now use the star marked "E" in the chart above
star E = USNO-A2.0 0900-13636967 = GSC 00448-00243 = RA 18:49:01.91 Dec +00:33:46.2 (J2000)as the zero point on the differential magnitude scale.
I've made a table of the measurements themselves, with three different flavors of time. Here's the start of the table:
# Measurements of V603 Aql made at RIT Observatory, Jul_ 19, 2003 UT, # taken by Michael Richmond. # All data taken with 12-inch Meade LX-200 + V filter + SBIG ST-8 CCD # Each exposure 30 seconds long; the tabulated times are midexposure # and accurate only to +/- 1 second. # 'mag' is the difference between V603 Aql and star E = GSC00448-00243 # # UT day JD-2,450,000 HJD-2,450,000 mag Jul_19.06634 2839.56634 2839.57159 -1.107 Jul_19.06689 2839.56689 2839.57214 -1.094 Jul_19.06744 2839.56744 2839.57269 -1.034
Last modified 7/19/2003 by MWR.