Getting into it

Today after our morning meeting I dove into working through some examples of the photometry techniques I read about earlier this week. Rather than bog myself down trying to work with the hubble images as we learned today that we likely won’t even be using photutils to perform the photometry on the hubble images. Photutils is still important to understanding the mechanisms of photometry and developing proficiency in the “cornerstones” of photometry. Today my most fruitful exercise has been on getting a source masking background detection program working. I went through much of the same process as they did in the photutils tutorial and heavily annotated the code to explain my understanding of exactly what is going on with each command. I got the same results as they got in the photutils tutorial. The method of masking sources to detect background seems to produce the best results of all the methods that the photutils tutorial talked about, so it is good to know how to do it. The parameter values that they used in the tutorial produce the most accurate results, but it is interesting to watch how the results change with different values. The one part of the source masking code that I feel a little unclear on is how the signal to noise ratio is calculated for a particular pixel. I read based on poisson statistics the S/N is just sqrt(S). This seems reasonable, however, I am curious how photutils particularly calculates the S/N.

Next Steps

I have created two similar documents in the Rory’s Codes folder on NGC6819 to practice source detection and aperture photometry. I think that this simpler methodology will allow me to start making more progress.

Concluding

I am happy to be making progress and writing code. I think that going forward I will continue to do research in the mornings as I feel my mind is fresher in general in the morning and I can get up early to start early and get a full half day in before lunch and painting.