On the night of Aug 06/07, 2014, I observed the cataclysmic variable star ASAS-SN14cv. It was roughly steady at roughly V = 16.4, but the conditions were bad, and the data is short and noisy. You can read more about ASAS-SN14cv, which was discovered only recently, at
The main setup was:
Notes from the night
Below is a graph showing the sky brightness as a function of time during the observing run. Note the bumps and big gap due prolonged clouds.
Below is a graph showing the FWHM as a function of time during the observing run.
Here's a chart of the field of ASAS-SN14cv, which is at
RA = 17:43:48.58 Dec = +52:03:46.8 (J2000)
Some of the reference stars marked above have magnitudes in the UCAC4. Specifically, star "A" above is
The television camera on the finder scope shows the following when we're pointed at ASAS-14cv. North up, East left, field about 1 degree on a side.
The image adjustment factor graph shows frequent jumps and the gap caused by clouds.
Using aperture photometry with a radius of 4 pixels (radius of 7.4 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. I used the UCAC4 V-band magnitude of star "A" to convert the ensemble instrumental magnitudes to a reported "V"-band magnitude (but remember, it's a clear filter).
Sigma-vs-mag plot: The two brightest stars were both saturated, and so I gave them zero weight in the ensemble calculations. The target is around instrumental mag 6.5; it does not stand out from its noisy neighbors.
The target, shown in green, shows no obvious change, perhaps due to the very large scatter.
You can see my measurements of the star in the ASCII text file below. The first few lines are shown here:
# Measurements of ASAS_SN14cv made at RIT Obs, Aug 7, 2014 UT, # in poor conditions. # by Michael Richmond, using 12-inch Meade and SBIG ST-8E CCD. # Exposures 45 seconds long, no filter. # Tabulated times are midexposure (FITS header time - half exposure length) # and accurate only to +/- 1 second (??). # 'mag' is a differential magnitude based on ensemble photometry # using a circular aperture of radius 7.4 arcseconds. # which has been shifted so UCAC4 711-058151 has mag=11.518 # which is its V-band mag according to UCAC4. # # UT_day JD HJD mag uncert Aug07.06169 2456876.56169 2456876.56256 16.309 0.145 Aug07.06240 2456876.56240 2456876.56327 16.153 0.126 Aug07.06311 2456876.56311 2456876.56398 16.385 0.148
Last modified 8/07/2014 by MWR.