UT Oct 11, 2021: photometry of V1004 Cyg

Michael Richmond
Oct 11, 2021

On the night of Oct 10/11, 2021, I observed the eclipsing binary star V1004 Cyg for one of our capstone projects.

There were no problems with equipment, but clouds ruined a brief chunk of time near the end of the run. Nonetheless, this data fills a gap in the star's phase coverage.

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
• no guiding (see notes below)
• focus values:
  • V: 0.612 yielding FWHM 1.8 (!) at T = 67/19
  I set the focus to a mid-point, 0.642, so both B and V would be slightly out of focus. After a short time, I shifted it to 0.632 to give equally poor images for B and V.
• camera ran at T = -19 C

Notes from the night:

• heavy clouds ruined about 40 minutes, and made another hour noisy
• thin waxing crescent Moon was no problem
• tried using the guider, but MaximDL froze after taking six images. Re-started and did NOT use the guider afterwards.
• no skunks, though I might have scented one
• temperature dropped to 61/16 when I quit at 1:07 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 heavy clouds in the second half of the run, which eventually cleared.

The FWHM graph below shows quite a bit of variation, and bogus values when clouds were heavy.

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 0.010 mag in both bands. The target is the fainter big outlier; the brighter outlier is a variable with unknown period.

The change in zeropoint shows the effects of clouds.

Last modified 10/11/2021 by MWR.