On Jun 28, 2003, EST, Tracy Davis and I decided to put the 12-inch Meade LX-200 into some serious use: photometry of 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 20 arcminutes wide.
I measured the instrumental magnitude of each star with aperture photometry, using a radius of 6 pixels = 13.8 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.
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, D, E and F.
After making the ensemble solution, I looked at the values for star "D". 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 were only 12 out of 356 "BAD" images.
Here's a closeup of the variation in V603 Aql itself:
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, Jun_ 29, 2003 UT, # taken by Michael Richmond and Tracy Davis. # 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 BD+00 4022 = GSC 00448.00731 # # UT day JD-2,450,000 HJD-2,450,000 mag Jun_29.11358 2819.61358 2819.61893 3.252 Jun_29.11588 2819.61588 2819.62123 3.244 Jun_29.11759 2819.61759 2819.62294 3.225
Last modified 6/29/2003 by MWR.