V603 Aql: Jul 01, 2003 EDT

On Jul 01, 2003, EDT, I used the 12-inch Meade LX-200 to measure 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 early, for the first two hours or so.
• Clouds appeared at 4:00 AM, just as sky was getting bright.
• Air temperature was warm: it started at 22 C and dropped to about 17 C during the night. I was able to run at CCD temp -10 C.
• The autoguider had troubles, even when there were no clouds. It frequently moved the telescope a short distance from the "standard" position, then slowly moved back. This caused many images to be trailed or show "double exposure" effects. As a result, I had to discard many more images than usual: about one quarter of the 360 images.

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 5 pixels = 11.5 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 "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. Originally, there were 356 images. After discarding those with trails or "double exposures" or obvious clouds, 283 remained. There were only 3 "BAD" out of these 283 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, Jul_ 2, 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 BD+00 4022 = GSC 00448.00731 
# 
# UT day      JD-2,450,000  HJD-2,450,000   mag 
Jul_02.10696     2822.60696   2822.61234   3.252 
Jul_02.10752     2822.60752   2822.61290   3.235 
Jul_02.10808     2822.60808   2822.61346   3.243 

• download the entire table (plain ASCII)

Last modified 7/02/2003 by MWR.