UT Dec 13, 2021: Photometry of WZ Cyg and BX Peg

Michael Richmond
Dec 13, 2021

On the night of Dec 12/13, 2021, under good conditions, Sean Kloss I acquired images of the eclipsing binary systems WZ Cyg and BX Peg as part of capstone projects.

We acquired data on WZ Cyg first, in order to fill the last remaining gap in the light curve; after that, we made a brief run on BX Peg, mostly as practice for a longer run tomorrow night. All went well.

WZ Cyg

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
• I focused mid-way between the best positions for B and V filters
  • foc in V = 0.447 yielding FWHM 3.4 at T = 40 / 4
  • foc in V = 0.475 yielding FWHM ??? at T = 37 / 2
• camera ran at T = -20 C

Notes from the night:

• no clouds, but always looking relatively low in the sky
• bright first quarter Moon in the E, far from target
• no skunks. Sob.

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 mostly clear early, but mostly cloudy later.

The FWHM graph below shows a gradual increase due to airmass, as well as a small jump when I nudged the focus up by 0.020 units.

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 0.008 mag in B.

The change in zeropoint shows a steady climb due to airmass.

BX Peg

RIT student Sean Kloss is studying the long-term orbital behavior of the contact binary BX Peg. He and Jen Connelly have been observing it for the past few weeks, but this was my first night working on this system.

We acquired the field after a bit trouble and took a series of 66 images in the V-band alone. As the graph below shows, we caught one of its minima, though there isn't as much data on either side as we'd like.

Last modified 12/17/2021 by MWR.