UT Nov 09, 2021: photometry of V1004 Cyg and WZ Cyg

Michael Richmond
Nov 12, 2021

On the night of Nov 08/09, 2021, Remi Schneieder and I observed the eclipsing binary star V1004 Cyg for one of our capstone projects. The measurements would fill in mission portion of the light curve. I later observed WZ Cyg for a short time as well.

The weather was fine. MaximDL froze soon after the start of the run, but after we stopped using the guider, it behaved.

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 30 seconds
• images binned 2x2
• guiding with 3-second exposures, briefly, then no guiding
• focus values:
  • V: 0.558 yielding FWHM 2.2 T = 62/16
  • V: 0.551 yielding FWHM 3.6 at T = 52/11
  I set the focus to a mid-point, 0.030 higher than the V-band value, so that both V and B would be out of focus by a similar amount.
• camera ran at T = -20 C

Notes from the night:

skies were clear
• we started guiding with 3-sec exposures, but after just 11 images, MaximDL froze. After restarting it, we didn't guide, and there were no further problems.
• no skunks
• quit at 10:14 PM, when the field was low, and switched to WZ Cyg

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 clouds, just a gap when MaximDL froze.

The FWHM graph below shows small variations, but nothing major.

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 0.005 mag in B. The target is the smaller of two outliers around instrumental mag 3.6, and the bright outlier at mag 0.7 is the variable with unknown period.

The change in zeropoint shows that the skies were clear.

WZ Cyg

Notes from the night:

• sky remained clear
• no Moon at this time; it had already set
• stopped at 11:32, T = 51/11

The object is located at

  RA = 20:53:06.78  Dec = +38 49 40.7   (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. The bright star P is the ninth-magnitude HD 198975.

Label	B	V
A	11.480	10.951
B	11.475	10.978

I'll use star "A" to shift my instrumental magnitudes to the V-band scale.

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 significant clouds.

The FWHM graph below shows no changes over this short run.

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.

The change in zeropoint was caused by increased airmass.

Last modified 11/12/2021 by MWR.