Photons: gotta catch ’em all

In the beginning of March, we went for an observation at the good and old Pico dos Dias Observatory (OPD), here in Brazil. I think it was the first time I went there during summer, which is the rainy season around these parts, so it’s not actually a good time for observations. We wanted to assess the B&C 0.60 m telescope in its potential to do followup observations for KELT (Kilodegree Extremely Little Telescope – pretty funny name: a bit of a satire on ESO’s “very large” telescopes, I imagine), which surveys the sky looking for hot Jupiters around bright stars. So yeah, we went there to hunt some exoplanets.

To do that, we used differential photometry, a method that compares how the brightness of different stars in a given field of view vary with time. In our case, we wanted to see how the brightness of the exoplanet-host dipped when a transit occurred. To do that, we need as many photons as possible to fall on our detectors, so we can have measure the dip with a bigger certainty. Results were very interesting, and I will write a more complete blog entry about our observations in the near future. But, while we were there trying to catch the light (or rather, the shadow) of exoplanets, I was, as always, trying my hand on some night sky pictures.

While I left the telescope doing a very long series of exposures, I set out taking my camera and tripod to do some imaging. And during one of my first trials, I was lucky enough to have a really bright meteor cross the sky and go over the 1.60 m telescope, and even more lucky to have my camera exposing at the time. And further lucky to have set a high ISO, so the meteor stood out beautifully in the picture. Unfortunately, since it was one of the first pictures, the camera wasn’t focused very well (in fact, it was pretty terrible), so it didn’t end up as good as it could be. Also, the Moon was 88% illuminated, so we get this effect of “daylight with stars” in long exposures (in all pictures, click to embiggen).

A bright meteor over the 1.60 m telescope, Mar 02, 2015, UTC 03h42. It was the first time in my life I got a meteor on picture.

However, things weren’t that bad, because the sky went completely dark after around 4 AM, when the Moon set, so there was this short window of darkness until the twilight, and I was eager to take advantage of it. I haven’t had many chances of taking pictures in really dark places with really dark conditions before, so this was a good opportunity.With the help of some bright stars, I managed to focus the camera and I took these two following pictures. The first one was taken using ISO 3200 and, luckily enough, I got another meteor (a dimmer one, though) and a satellite! The second one was taken with ISO 1600, which has less noise, but it is less sensitive, and so I had to take more exposures, resulting in longer star trails (I don’t have an equatorial tracking tripod). As you can imagine, we have to work with a trade-off between more light and noise/trails.

The Milky Way bulge, a meteor and a satellite. 15×10 s of exposure, ISO 3200, F3.5. The light pollution comes from the cities around the Mantiqueira Mountain Range.
The Milky Way bulge, no meteor and no satellite on this one, plus star trails. 20×10 s of exposure, ISO 1600, F3.5.

Here are two other shots taken aiming towards the domes of the observatory, and they are probably my favorite ones. Not only because they look fairly good, but because it was actually very fun to take these shots. The site was so dark, that it was hard to find my way around the observatory until my eyes didn’t get used to the darkness (it took about 10 minutes). Once your pupils are fully open, we can see so many stars in the sky that it is difficult to find the asterisms of the constellations.

The Milky Way bulge over the dome of the 1.60 m telescope at Pico dos Dias Observatory.
The southern band of the Milky Way is very rich. In this picture, you can find the Coalsack Nebula, the Eta Carinae nebula and various star clusters.

I think those were very productive nights. We obtained good results from the observations, I got a chance to take pictures in really dark conditions, and food was good. The food from OPD is never a let down. Word is that, when the weather is bad, astronomers like to spend their time lounging at the 1.60 m telescope pantry. Luckily we didn’t need to do that.



Photons: gotta catch ’em all