UT Oct 29, 2022: Photometry of V1004 Cyg through clouds

Michael Richmond
Oct 30, 2022

On the night of Oct 28/29, 2022, I observed the eclipsing binary star V1004 Cyg for a capstone project. I was hoping to capture the one section of its light curve that we need to confirm, but the weather did not cooperate. Rats.

V1004 Cyg

We 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 40 seconds
• images binned 2x2
• no guiding
• focus values:
  • V: 1.093 yielding FWHM 2.7 at T = 53/12
  • B: 1.143 yielding FWHM 2.8 at T = 53/12
  I set the focus to 1.113 units. About 2 hours later, I checked the focus again.
  • V: 1.050
  Set focus to 1.070.
• camera ran at T = -20 C

Notes from the night:

• thick clouds for the first three hours (when I really needed data), somewhat clear for the last hour
• Moon set before clouds cleared up
• no skunks

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 to use 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	r'
C	12.717	11.803	11.41
E	12.840	12.182	11.93

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 lots of clouds early.

The FWHM graph below shows a large PSF early, better late after refocusing (and no clouds).

Using aperture photometry with a radius of 10 pixels in B and V (binned 2x2, each pixel is 1.24 arcsec, so a radius of 12.4 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 0.009 mag in V. Bleah.

The change in zeropoint shows big variations due to clouds, until the end of the run.

And we missed the important part of the light curve tonight. Darn it.