V603 Aql: Jun 28, 2003 EST

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.

The plan:

• the Meade 12-inch telescope + f/6.3 focal reducer + SBIG ST-8E CCD
• V-band filter
• 30 second exposure times
• no flatfielding, since the main feature of images is an internal reflection off the focal reducer

Notes from the night

• Broken clouds passed in waves during the first few hours, causing the guider to lose track of its star once. After 1 AM, the sky was nearly always clear.
• Air temperature was warm: it started at 24 C and dropped to about 20 C during the night. I was able to run at CCD temp -8 C.
• The FWHM of stellar images remained steady at about 2.6 pixels (binned 3x3) to 3.3 pixels all night long. We didn't refocus.

Here's a chart of the field of V603 Aql, taken with our equipment: the field is about 20 arcminutes wide.

Note that

• star A = HD 174066 = BD+00 4023, V mag = 8.5
• star B = BD+00 4022 = GSC 00448-00731, V mag = 9.9
• the variable, V603 Aql, is roughly V mag = 11.

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 

• download the entire table (plain ASCII)

Last modified 6/29/2003 by MWR.