June 3, 2015 UT: HH UMa

Michael Richmond
June 3, 2015

On the night of June 2/3, 2015, Kaitlin Schmidt and I observed the eclipsing contact binary star HH UMa.

In addition to this little observing project, some students came to the observatory to learn how to operate the equipment.

• Sravani Vaddi
• Davide Lena
• Triana Almeyda
• Jam Sadiq

Undergraduate student Tevfik Ozkaynak came to help out with the observing. He's come out a number of times to help me during long observing runs.

The main setup was:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• SBIG ST-9E CCD camera with clear filter
• 20-second guided exposures

Notes from the night

• Conditions were fair: mostly clear skies toward the target, with thin cloud to the east.
• A bright full moon, but low and on the other side of the sky.
• Twilight sky flats.
• Divided all raw frames by 2 to avoid exceeding the 15-bit limit of XVista software.

HH UMa

This object is a nice eclipsing binary star with a continuously varying light curve; a number of papers describing it provide many details, including a period of 0.375494 days = 9.01 hours.

Here's a chart of the field of HH UMa which is at

      RA = 11:04:48.1      Dec = +35:36:27     (J2000)

The chart is about 12x12 arcminutes.

Among the labelled stars is

  A     UCAC4 629-045393    V = 12.721

The bright star to the south of HH UMa and "E", BD +36 2151, is slightly saturated in these unfiltered 20-second images.

Below is a graph showing the sky brightness as a function of time during the observing run. The brief dip was caused when we closed the dome slit, then re-opened it to position the panel at the top location. No evidence for clouds.

Below is a graph showing the FWHM as a function of time during the observing run.

I used 20-second exposures during this observing run. The target had about 16,000 peak counts/2 with this exposure time, which is a nice, high level.

Using aperture photometry with a radius of 4 pixels (radius of 5.7 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 plot: The brightest star is the saturated BD +36 2151, and the second-brightest star is the target.

Image adjustment factor: note again the lack of clouds.

The target, shown in green, shows a steady increase in brightness during the two-hour run.

Here's a closeup, with star "A" shifted for easier comparison.

Last modified 6/03/2015 by MWR.