INTERVIEW

Expert astrophotographer Chris Baker takes us behind the scenes as he captures his magical and mysterious images of deep space

We chat to astrophotography expert Chris Baker as we find out what it takes to shoot stunning images of the mysterious realm of deep space

As far as photographic genres go, there aren’t many that are as specialised as astrophotography. While there are a plethora of challenges faced by photographers shooting subjects on Earth, attempting to capture quality, detailed colour images of objects several light years away raises the workload to new levels. While this field of imaging may be seen as resourcedependent and therefore prohibitively expensive to many, deep space photographer Chris Baker (cosmologychris.co.uk) believes anyone can enjoy shooting celestial subjects. “What I do is relatively advanced, timeconsuming, a serious passion and certainly not cheap,” admits Chris. “However, please don’t think you need an observatory on a mountain in Spain, many thousands of pounds of equipment and a lot of time, to start observing the heavens or photographing deep space. Good results can be achieved with modest equipment under light-polluted skies, albeit with a little dedication.”

Chris has worked in astrophotography since 2001, although this stemmed from a life-long passion for astronomy. Through the years he has become an expert in both areas, contributing to multiple major publications and media, including The Sky at Night for the BBC. After graduating with a degree in Chemistry from the University of York, Chris has used his scientific background to great effect. “I don’t photograph objects within our Solar System, so no planets for example – I image objects that are much further away. These are a few hundred light years away, to over a billion light years. They are known as deep space objects,” he explains. The focus of his images is as varied as it is fascinating. “The light has travelled through the universe, over thousands or even millions of years to reach my camera. I am passionate and dedicated in my pursuit of an outstanding photograph. It may be nebulae which are giving birth to stars like our sun, a gigantic galaxy made up of a trillion stars, or a star spectacularly disintegrating in vivid colour.”

The images Chris captures are stunning in both subject matter and creative execution, something which he feels is important for inspiring an interest in space within his viewers. “Such images make the cosmos more accessible and bring these wondrous distant objects closer to home,” he explains. “I am interested in investigating the cosmos through the language of art, as an alternative to the language of physics, which is baffling to many people. I see both physics and art to be simultaneous descriptions of reality, which are equally valid. Like many scientists, I was initially drawn to astronomy by a deep sense of wonder and awe for the beauty, enormity and mystery of the universe.”

Chris then explains the extensive process behind the creation of his deep space images. “There is a significant difference between conventional photography and deep space photography, driven by the amount of light reaching the camera. Deep space objects are extremely faint, so the exposure times required are tens of hours rather than a few seconds or a fraction of a second, as in conventional photography. This leads to radically different techniques and equipment being employed. The first step is to plan what is to be photographed. Different objects are available at different times of the year and are visible from different parts of the world, so clearly the object must be available from my location. Ideally, I want the object to be high in the sky and visible most of the night. I also decide which filters are to be used and the exposure times. The filters govern the type of colour data gathered, which is later used to create the colour image.” From Chris’ description, it is clear that one of the greatest investments astrophotographers

“Good results can be achieved with modest equipment under light-polluted skies, albeit with a little dedication”

must make is one of time, as the creation of a quality image can take several days. “To get the data I need to create a good colour image I will photograph through three, four or five filters. I aim for up to 50 hours of total exposure time gained over many nights. For many reasons, it is not possible to have a single exposure of hours. Therefore, the task is cut into manageable chunks by taking what are known as ‘sub frames’. These are photographs with exposure times of minutes

rather than hours. Typically, I will take sub frames of 20-25 minutes each, which are built up over many nights through each filter. Every morning I will discard those that are imperfect – imperfections can occur for a variety of reasons, perhaps poor visibility, an aircraft or satellite leaving a trail right across the image, poor focusing or a software error. l discard in the region of 30 per cent of all the sub frames. This means I need even more time to gather enough data!” To accurately capture sharp and clean image files, Chris must take three further types of image: dark frames, bias frames and flat fields. “Dark frames are images taken with the shutter closed and are required to remove the thermal and electronic noise. The same number of images is taken as the light sub frames, with the same exposure. Bias frames are extremely short exposures with the shutter closed. Not all the pixels on a CCD chip have a value of zero – bias frames apply it to dark and light sub frames, to bring all the pixels on the sensor to the same starting value. Flat fields are images taken of a dusk or dawn semi-light sky – they are required [to remove] dust or dirt on lenses, filters or the camera chip.”

Once all of this work has been done, Chris’ resulting image frames can be combined in software, to produce the magical final compositions. He uses several applications to enhance his merged files. “The first stage is to stack the individual sub frames for each filter, then to combine the red, green and blue data into the colour image. At this early point, the beauty and detail are still buried somewhere in the data and need to be teased out, extracted and carefully enhanced. I use a range of software, including Maxim DL, PixInsight and Adobe Photoshop to create the final image.” While this is an intensive process, the images shown here demonstrate the capability of modern hardware and software to capture

“Such images make the cosmos more accessible and bring these wondrous distant objects closer to home”