UT Sep 25, 2021: photometry of V1004 Cyg

Michael Richmond
Sep 25, 2021

On the night of Sep 24/25, 2021, I observed the eclipsing binary star V1004 Cyg for one of our capstone projects.

There were no problems with equipment or weather, and I was able to acquire a good set of measurements.

V1004 Cyg

I acquired images of the eclipsing binary system V1004 Cyg as part of a capstone project.

The main setup was:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ATIK 11000 CCD camera
• B, V filters, exptime 30 seconds
• images binned 2x2
• guiding with exptime 3 seconds
• focus values:
  • B: 1.326 yielding FWHM 2.7 at T = 63/17
  • V: 1.264 yielding FWHM 2.6 at T = 63/17
  I set the focus to a mid-point, 1.294, so both B and V would be slightly out of focus. The plan worked fine.
• camera ran at T = -20 C

Notes from the night:

• maybe one brief episode of very light clouds
• waning gibbous Moon made the sky pretty bright, but it was far from the target
• no skunks. Sigh.
• temperature dropped to 52/11 when I quit at 2:00 AM.

The object is located at

  RA = 19:50:29.44  Dec = +33:08:32.2    (J2000)

A chart of the field is shown below. The size of the chart is about 31 x 26 arcminutes.

I've marked the location of several comparison stars as well. You can find reference magnitudes for these stars at the AAVSO:

• AAVSO chart for the field
• table of magnitudes from the AAVSO: sequence X27032O

I used the star marked as "C" in the picture above, or "118" in the AAVSO charts, to shift the instrumental magnitudes to the standard scale.

Label	B	V
C	12.717	11.803

I took a photo of the finder TV's screen when pointing to this target; this could be a useful reference for the future:

The sky value shows no changes due to clouds.

The FWHM graph below shows no big changes.

Using aperture photometry with a radius of 7 pixels in B and V filters (binned 2x2, each pixel is 1.24 arcsec, so a radius of 8.7 arcsec), I measured the instrumental magnitudes of a number of reference stars and the target. 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.

Sigma-vs-mag plots show that the floor was about 0.007 mag in both bands.

The change in zeropoint shows a brief spike when I closed the dome slit briefly in order to raise the bottom panel.

Last modified 9/25/2021 by MWR.