Simultaneous photometry of hundreds of objects in AstroImageJ

This summer, I saw Tonny Vanmunster's  Facebook post: "Phoranso processed nearly 1,000,000 observations in a single run" -- about photometry of thousands of objects using his new Phoranso software. Nearly 1,000 FITS files, each containing over 1,000 variable stars, were analyzed.

Well, it was an impressive result. 'Can I achieve something like this using free software?' I asked myself. For many years, I've been using AstroImageJ -- a program with a not-so-polished interface, yet one that reliably does what it's supposed to.

Moreover, I had a task for it. I had just conducted a test observation session after a long break -- a ~3.5-hour observation of the vicinity of Stephan's Quintet. Not all frames were perfect (guiding was poor, probably due to gusts of wind), but I eventually selected 150 frames with 60-second exposures. Here's one of them:

Using a small Python script, I extracted the coordinates of 864 stars and had AstroImageJ place the apertures on the image:

 

I picked one of the stars as a reference -- after checking it wasn’t variable -- and ran the photometry.

I hadn’t noted the exact time, but the process took about 1.5 hours. As a result, I obtained approximately 130,000 instrumental magnitudes. Some of them were saturated, so I excluded those.

I wrote another Python script that generated a preview HTML file containing all the light curves. It looked like this:

 

 

 

Among hundreds of noisy patterns, I spotted several well-defined light curves that clearly belonged to variable stars. Well, these were known variables. Still, the approach worked -- and now I have a tool for performing simultaneous photometry on all the stars I capture in a single session.

One of them turned out to be quite interesting, and I'm now investigating it more closely.