UT Oct 08, 2021: Photometry of WZ Cyg

Michael Richmond
Oct 10, 2021

On the night of Oct 07/08, 2021, under fair conditions, I acquired images of the eclipsing binary system WZ Cyg as part of a capstone project.

The night was very humid, and once again ice crystals formed on the camera's window. I raised the CCD temperature to +1 Celsius and continued to acquire images; the results are noisy, but not too bad.


WZ Cyg

The main setup was:

Notes from the night:

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.

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 big dip is due to artifacts when I raised the CCD temperature.

The FWHM graph below shows a gradual rise -- no big deal.

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 0.011 mag after I removed images with large outliers.

The change in zeropoint was largely driven by airmass.


Last modified 10/10/2021 by MWR.