V603 Aql: Jul 03, 2003 EDT

On Jul 01, 2003, EDT, Tom Schwarting and 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

• Just a few light clouds for 20 minutes or so around 11 PM; otherwise clear.
• Sky was hazy and bright, though
• Air temperature was hot: it started at 25 C and dropped to about 21 C during the night. I ran at CCD temp -5 C.
• Upgrading MaximDL to V3.10 fixed the autoguider problems: there were no more "empty" frames. Rah!

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
• star E = GSC 00448-00243 = USNO-A2.0 0900-13636967
• 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. New for tonight: 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. I looked at data on fainter stars over several night, and noticed that they varied in unison; I believe it was due to star "B" dominating the solution. So, I won't include star "B" in the solution from now on.

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, and P (the brightish star in extreme lower left corner).

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 were only 3 "BAD" out of 396 images.

Here's a closeup of the variation in V603 Aql itself:

New for tonight
I've modified the way I report the differential magnitudes. I now use the star marked "F" in the chart above

      star F  =  USNO-A2.0 0900-13636967 
              =  GSC 00448-00243
              =  RA 18:49:01.91  Dec +00:33:46.2  (J2000)

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_ 4, 2003 UT, 
#   taken by Tom Schwarting and 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_04.08954     2824.58954   2824.59492  -0.975 
Jul_04.09015     2824.59015   2824.59553  -0.955 
Jul_04.09196     2824.59196   2824.59734  -0.989 

• download the entire table (plain ASCII)

Last modified 7/04/2003 by MWR.