Jun 30, 2014 UT: ASAS-SN14cv and ASAS-SN14cl

Michael Richmond
Jul 01, 2014

On the night of Jun 30/Jul 01, 2014, I observed the cataclysmic variable stars ASAS-SN14cv and ASAS-SN14cl. You can read more about these stars, which were both discovered only recently, at

ASAS 14cv is now barely varying, but ASAS 14cl is showing large, beautiful superhumps.

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.

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


ASAS-14cv

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.

Image adjustment factors show minor bumps due to light 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 target had a "V"-band magnitude of roughly 12.5, a decrease of about 0.3 mag since 3 nights ago.

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, Jul 1, 2014 UT, 
#    in fair conditions, 
#    by Michael Richmond, using 12-inch Meade and SBIG ST-8E CCD. 
# Exposures 30 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
Jul01.07825     2456839.57825  2456839.57965  12.525  0.005 
Jul01.08000     2456839.58000  2456839.58140  12.521  0.005 
Jul01.08059     2456839.58059  2456839.58199  12.507  0.005 



ASAS-14cl

Here's a chart of the field of ASAS-SN14cl, which is at


      RA = 21:54:57.62     Dec = +26:41:16   (J2000)

Some of the reference stars marked above have magnitudes the UCAC4 AAVSO chart 13493SS. Specifically, star "B" above is

The television camera on the finder scope shows the following when we're pointed at ASAS-14cl. North up, East left, field about 1 degree on a side.

Conditions were good until the last hour, when (I am guessing) clouds passed through; I didn't see any visually, but the image adjustment factor jumps.

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 AAVSO V-band magnitude of star "B" to convert the ensemble instrumental magnitudes to a reported "V"-band magnitude (but remember, it's a clear filter).

The target is the bright star with larger scatter than its peers.

The target had a "V"-band magnitude of roughly 13.1, about 0.1 mag dimmer than last night.

Grab the text file below for all the RIT measurements of ASAS-SN14cl. The header of the file is shown below.

# Measurements of ASAS_SN14cl made at RIT Obs, Jul 1, 2014 UT, 
#    in fair conditions, 
#    by Michael Richmond, using 12-inch Meade and SBIG ST-8E CCD. 
# Exposures 30 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 584-123918 has mag=12.335 
#    which is its V-band mag according to AAVSO chart 13493SS.  
# 
# UT_day             JD            HJD        mag    uncert
Jul01.19370     2456839.69370  2456839.69584  13.180  0.011 
Jul01.19428     2456839.69428  2456839.69642  13.199  0.012 
Jul01.19486     2456839.69486  2456839.69700  13.185  0.012 


Last modified 7/01/2014 by MWR.