IN­TER­VIEW

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

Digital Photograper - - Contents -

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”

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