Resources

We have made some screencasts showing how to perform the functions in JS9 which you may find useful.

1. You'll need to use an internet browser (such as Firefox, Google Chrome, Internet Explorer) and open up the photometry program, JS9.

2. In JS9, open a data file from the Gaia16agf folder - any one will do but you may find it easier to work through these in date order. The folder contains 16 images taken by Faulkes Telescope North. The file name represents the date the image was taken (20160302 = 2nd March 2016). Note that this zipped file is ~ 200 Mb so may take a minute or so to download.

Figure 1: Finder chart for the supernova, Gaia16agf and its
comparison stars

3. Familiarize yourself with the functions in JS9 such as Zoom, and Contrast using the 'JS9 Manual' to help you. You may want to try to identify the target (the supernova; Gaia16agf) and the two suggested comparison stars from the finder chart jpeg (see Figure 1). These are the three stars you will perform photometry on.

4. For each file (you will probably find it easier to open and close each in turn), perform photometry on the stars shown in the finder - using the top slider, try to set the number of pixels to around 240. This represents the area of the aperture so corresponds to an aperture radius of about 9 pixels. You'll need to record three values for each of the stars; the Star Brightness, Sky Median and Number of pixels.

6. Using the 'Magnitude calculator' spreadsheet, type the values from JS9 for each of the three stars for each of the 16 frames - you may ignore the numbers after the decimal point. For each of these measurements, you will need to record 'Star Brightness', 'Sky Median' and 'Number of Pixels'.

 

When you've created your lightcurve, we'd be delighted to hear from you and especially to see what you've produced. If all has gone well, it should resemble the dashed line in Figure 3 here. Measuring the peak value from your lightcurve gives you a value you can add to the Hubble plot. You can e-mail us to find out more using supernovae 'at' schoolsobservatory.org

Along the way, if you have problems, you might want to check our FAQs.

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