On the night of Jun 19/20, 2014, I observed the cataclysmic variable star ASAS-SN14cl. You can read more about this star, which was discovered only recently, at
This was my first observing session in about two months, so there were a number of minor items that I had to fix.
The main setup was:
Notes from the night
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
I took 30-second guided images through clear filter. There's a good guide star available if the target is placed on the chip at (353, 143). After discarding the bad images, I was left with 164 images.
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 second-brightest star below; its scatter is just a bit larger than that of stars of similar brightness.
The target had a "V"-band magnitude of roughly 12.0, and it showed just a little bit of gradual, slow variation over the course of the 2.4 hour observations:
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, Jun 20, 2014 UT, # in good 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 Jun20.14007 2456828.64007 2456828.64140 12.105 0.007 Jun20.14065 2456828.64065 2456828.64198 12.104 0.007 Jun20.14124 2456828.64124 2456828.64257 12.085 0.006
Last modified 6/20/2014 by MWR.