Photometric measurement of supernova SN 2023ixf

A new supernova went off in M101, the Pinwheel galaxy. After imaging it once, I also tried my hand at some photometry. Due to a long spell of bad weather, I was able to perform my first measurement more than one month since the discovery and more than two weeks since taking my first image.

To this end I:

  1. Took six 5-minute exposures with my QHY163M CMOS mono camera through a 10-inch RC scope and an L filter;
  2. Properly calibrated the six raw frames;
  3. Generated a star chart using AAVSO's Variable Star Plotter with labels and magnitudes of reference stars;
  4. Used Maxim DL's photometry tools to tag the reference stars (whose V-band magnitude is known) in the field of view and plot the magnitude estimates (see pictures below)
Calibrated 5-minute exposure of M101 with reference stars tagged
Esimated magnitudes of reference stars and SN 2023ixf (labeled "sn")

The picture above depicts a linear, screen-stretched calibrated frame with reference stars tagged, while the picture below contains the plot of the reference star magnitudes and the resulting magnitude estimates of supernova SN 2023ixf.

A sample of only six frames is probably not accurate enough. Anyway, the computation yields an estimate of 11.75 +/- 0.04 magnitudes for SN 2023ixf. This is reasonably consistent with the official measurements (see image at bottom with light curve from AAVSO) although there can be differences since a V filter is roughly equivalent to a green filter, while an L filter has a much wider bandwidth.

Bottom line: I don't know how reliable my estimate is, but it was a fun and interesting exercise nevertheless!

Appendix: how to plot AAVSO's light curves

  1. Open AAVSO's Enhanced LCG website;
  2. Type "sn2023ixf" in the "star name" field;
  3. Click the "Send" button.

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