UT Apr 02, 2024: Photometry of UX UMa

Michael Richmond
Apr 02, 2024

On the night of Apr 01/02, 2024, under fair conditions, RIT student Dylan Filosa and I acquired images of the eclipsing cataclysmic variable star UX UMa. The goal was to measure an eclipse of this system for the PHYS 373 "Observational Astronomy" class. Unfortunately, the clouds moved in just as the event was predicted to start.

UX UMa

This eclipsing system has a short period of about five hours; the eclipse is very deep, causing the star to fade from about V = 12.8 to V = 13.8.

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• B-filter 60-sec, V-filter 40-sec images
• images binned 4x4
• no guiding
• focus position on 12-inch:
  • in V: 0.370 yields FWHM 4.1 at T = 49/9

Notes from the night:

• thick cirrus at sunset, but soon after we started, the skies cleared for a few hours. Unfortunately, the clouds reappeared around 10:30 PM, and we had to stop before the eclipse began (which would have been close to 11:40 PM).
• no Moon visible
• camera at T = -20 C
• air temperature in the dome dropped from T = 51/10 at start of run to T = 41/5 at the end

The picture below shows an image of the field of UX UMa from this evening. The field of view is about 26 arcminutes high.

I've marked the location of several comparison stars.

  star       name                  B          V         
------------------------------------------------------
    A       BD +52 1720         11.40        9.82
    C       BD +52 1722         10.39        9.97
--------------------------------------------------------------------------

 

Here's the sky background over the course of the run. Note clouds at the start and at the end.

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. Note evidence for thick clouds again.