Let's put our aperture photometry skills to use by measuring the magnitude of supernova 2013ej in the galaxy M74.
Image courtesy of Martin Bernier
You can find a set of 5 images of the SN taken at the RIT Observatory in the directory called $dd/sn. You can copy them all to your own directory like so:
cp $dd/sn/*.fit .
Here's a chart, showing the SN and 5 nearby reference stars:
Your job is to
xlet aperture_radius= xlet aperture_innersky= xlet aperture_outersky=
Then, you need to find the real, calibrated magnitudes of these comparison stars. I suggest you look in the UCAC4 catalog.
Now, to place the instrumental magnitudes onto the calibrated scale, we need to shift the instrumental values by a constant amount so that they match up with the calibrated values.
calibrated mag = instrumental mag + K
If all went well, your measurements of the reference stars should end up equal to their calibrated values .... or, at least, close to their calibrated values.
Q: What is the magnitude of the supernova for each of your images? How well does your value agree with the light curve shown below? Q: What is the typical difference between your shifted magnitudes for the reference stars, and the actual catalog magnitudes of the reference stars?
Copyright © Michael Richmond. This work is licensed under a Creative Commons License.