UT Sep 25, 2026: Photometry of QR And

Michael Richmond
Sep 26, 2026

On the night of Sep 24/25 2026, under very good conditions, I acquired images of the cataclysmic variable star QR And.

Conditions were very good, and I measured the star over a period of about five hours. During the final 13 minutes of the run, the camera went into "bogus quick exposure" mode, in which it repeatedly recorded identical data after waiting just 1 second for an "exposure". This is a known failure mode for the software; fortunately, it didn't happen earlier in the evening.

QR And

This cataclysmic variable is the subject of a long-term study by the Center for Backyard Astrophysics.

  QR And    RA = 00:19:49.93   Dec = +21:56:52.1

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• V filter, exptime = 90 sec
• images binned 4x4
• guiding with 5-sec exposures, QR And at (708, 810)
• focus position on 12-inch:
  • V = 0.084 yields FWHM 2.1 pixels at T = 52/11
  See note below about the focus position.

Notes from the night:

• I didn't start observing until about 9:40 PM, 2.5 hours after sunset
• clear skies all night
• bright full Moon in the south during the entire run. Late in the run, moonlight would fall onto the front corrector plate of the telescope when I moved the dome into a new position. This had little effect on the photometry.
• camera at T = -10 C
• used dark frames of 90 seconds to match length of target images
• after the run was over, I noticed that the focus position was close to its maximum outer limit (focuser reading close to 0.000). I turned the silver focus knob about four quarter-twists CW, then used the electric focuser to find a rough new focus closer to the middle of its travel. New position will be around 0.643.
• temperatures cold: T = 54/12 around 9:06 PM, dropping to 42/5 when I closed at 3:10 AM.

The picture below shows a cropped image of the field of QR And from Sep 06/07, 2026. The field of view is about 20 arcminutes across.

I've marked the location of several comparison stars, with magnitudes and names taken from the AAVSO's table X43062GE.

  star       name                  B          V         
------------------------------------------------------
    A     000-BBB-469         11.743     10.647
    B     000-BBB-468         12.454     10.928
    C     000-BBB-450         11.951     11.425
--------------------------------------------------------------------------

 

When the target is centered, the finder TV shows this field:

Here's the sky background over the course of the run. The sudden jumps are due to moonlight falling on the telescope.

The FWHM was pretty steady.

The graph below shows changes in the photometric zeropoint of an ensemble solution of the instrumental magnitudes over the course of the run. No evidence for clouds. The set of identical readings at the end is due to the bogus readout issue.

Using aperture photometry with a radius of 7 pixels in V filter (binned 4x4, each pixel is 1.036 arcsec, so a radius of 7.3 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 in V filter was about 0.003 mag: excellent!

Here's the light curve of the target and some nearby comparison stars.

I've submitted these results to the AAVSO and the CBA.