UT Nov 02, 2022: Photometry of V1004 Cyg through clouds (again)

Michael Richmond
Nov 03, 2022

On the night of Nov 01/02, 2022, I (again) observed the eclipsing binary star V1004 Cyg for a capstone project. I was (again) hoping to capture the one section of its light curve that we need to confirm, but the weather (again) did not cooperate. I did make some half-decent measurements during the first and last hours of the run, and it might help to add those small segments to the light curve.

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: 1.068 yielding FWHM 1.5 at T = 57/14
  • B: 1.128 yielding FWHM 1.8 at T = 57/14
  I set the focus to 1.088 units. About 1.8 hours later, I lowered the focus by 0.010 units to 1.076. That definitely helped.
• camera ran at T = -20 C

Notes from the night:

• very humid but clear when I opened. Clouds arrived about an hour after I started measuring V1004 Cyg, stayed for about two hours, then mostly left for the last hour.
• Moon not important, low in west after sunset
• the seeing was very good -- I wonder if the very humid air is related to the stable air.
• autoguider seems to be connected to port COM1, not COM6. However, it isn't being read out properly, as far as I can tell. Perhaps the driver needs to be removed and replaced.

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 in the middle.

The FWHM graph below shows a nice PSF early, even better after I made a slight adjustment.

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. Not very good. Stupid clouds.

The change in zeropoint shows big variations due to clouds in the middle.

This incomplete dataset doesn't fill the gap in the overall light curve fully.