On the night of Aug 05/06, 2013, I observed SN 2013ej in M74. I barely beat the oncoming clouds, however, and only collected a few poor images.
The main setup was:
Notes from the night
SN 2013ej is a Type II supernova in the relatively nearby galaxy M74. It was discovered by the KAIT group some time (a week?) before maximum light. Here's a chart showing the galaxy, the SN, and some reference stars:
The reference stars marked above have magnitudes in AAVSO chart 12459CA, as follows:
letter B sigB V sigV R sigR I sigI B 13.012 0.019 12.510 0.019 12.154 0.019 11.834 0.019 F 13.848 0.026 13.065 0.022 12.622 0.025 12.152 0.027 H 14.338 0.029 13.692 0.024 13.329 0.029 12.964 0.030 I 14.832 0.027 13.912 0.023 13.416 0.026 12.939 0.030 K 15.192 0.034 14.613 0.027 14.275 0.034 13.915 0.036
There was no way to guide, given the clouds, so I went with 30-sec unguided images. After discarding the terrible images, I was left with 3 so-so images in B, 2 in V, 3 in R, 2 in I. The quality of these is poor, so the measurements will be somewhat unreliable.
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 magnitudes, plus color terms to convert the ensemble instrumental magnitudes to the standard Johnson-Cousins BVRI scale.
Results from this morning are:
filter mag mag_uncert Julian Date B = 12.715 +/- 0.028 (ens 0.005 zp 0.027) 2456510.82830 V = 12.553 +/- 0.032 (ens 0.027 zp 0.018) 2456510.82669 R = 12.321 +/- 0.043 (ens 0.006 zp 0.042) 2456510.82135 I = 12.291 +/- 0.052 (ens 0.034 zp 0.039) 2456510.82505
The uncertainties here are about equally due to noise in the images and transforming the instrumental magnitudes to the standard scale.
Grab the text file below for all the RIT measurements of SN 2013ej. All these values have been recomputed with the new color terms of UT 2013 Aug 05.
Last modified 08/06/2013 by MWR.