3.5 Lamitina. How to Photograph a Trillion Stars
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How to Photograph a Trillion Stars By Luke Lamitina ’22 Background Many people have seen the awe inspiring photographs taken over the years by telescopes such as the Hubble Space Telescope [3]. These canvases of ethereal structures that span over such vast distances have inspired generations and sparked social movements [6]. Astrophotography has a long and significant history spanning all the way back to 1839 when Louis Jacques Mandé Daguerre attempted to take the first long exposure of the moon. Due to technical problems with his telescope and tracking, his image ended up coming out fuzzy and distorted. Nevertheless, he had started the ball rolling on astrophotography, and it would only be a year before a man named John William Draper took the first successful photograph of the moon [1]. Although Daguerre wasn’t successful in his first attempt, he invented a new method called the Daguerreotype Process which allowed for much crisper images—not only revolutionizing the field of astrophotography, but photography as a whole [5]. Since John William Draper’s first picture of the moon, leaps in technology and innovation have allowed us to photograph some of the faintest objects in the cosmos. For example, in 1994 Robert Williams, the director of the Space Telescope Science Institute in Baltimore, Maryland, decided to use his director’s discretionary time on the Hubble Space Telescope in a way that seemed preposterous to many scientists at the time. His idea was to point the telescope at a place in the sky where there were thought to be no galaxies, or nebulae—somewhere in the sky that was believed to have nothing in it. After 10 days of exposure time, the Hubble returned what is now known as the Hubble Deep Field image [2]. This one picture had effects that completely revolutionized astrophysics as a whole. As an avid astronomer who partakes in exoplanetary research, a friend and I recently embarked on a new project: photographing a trillion stars. To do this, we photographed the galaxy known as M31, commonly referred to as the Andromeda Galaxy. At a distance of 2.5 million light years from Earth, Andromeda is the closest galaxy to the Milky Way. In 4.5 billion years, the two galaxies are predicted to collide and merge into a new galaxy deemed Milkdromeda [4]. Prior to this collision, my exoplanetary research partner and I set out to photograph Andromeda using the Allegheny Observatory. In this article I will overview our process and show the final result.
difficult to take good pictures of space if it is cloudy, even if the cloud level is low. The ideal conditions are a completely clear, cold winter night. On cold winter nights, the molecules in the air do not hold as much moisture as they do in the summer, leaving us with clearer images. Secondly, we must choose a target that is bright enough for our specific telescope to actually see. The system for giving objects in space a value that correlates with their apparent brightness is called visual magnitude. There are different scales that use different comparison stars as a reference, but the one that we used uses the star Vega as a reference. Objects dimmer than Vega are given a Vmag that is positive and objects brighter than Vega are given a Vmag value that is negative. Another important consideration is the size and distance of the object we are photographing. Depending on the camera one is using, some objects are either too small or too large to photograph. This can be due to the object’s physical size or its distance from the earth.
Figure 1: Locating an object with RA and DEC
Lastly, it is important to choose a target with a good right ascension (RA) and declination (DEC). RA and DEC is a coordinate system for the sky, similar to our coordinate system on the earth—they give a way of knowing where a star, galaxy, or nebula is located in the sky (see figure 1). In order to choose a good RA and DEC, multiple factors must be taken into account. The most important of these factors is how much atmosphere the light from our target must pass through before it reaches our Materials and Methods detectors. One thing you must know is that as light passes There are three major considerations when conduct- through any type of medium such as air, small variations ing astrophotography. The first is the weather. It is very in temperature, pressure, etc. cause the light to scatter. If
