The Milky Way

Cap­ture the light show at the cen­tre of our galaxy

NPhoto - - Nightscape Photography -

The stars we see in the night sky are from our lo­cal galaxy – An­dromeda. Our so­lar sys­tem is 26 thou­sand light years from the cen­tral ga­lac­tic core, and from our view, in­di­vid­ual stars within it be­come in­dis­cernible – com­bin­ing into a milky glow that gives the Milky Glow its name.

These pin­pricks of light are very faint, which makes pho­tograph­ing it par­tic­u­larly chal­leng­ing. To cap­ture the weak light you’ll need to be some­where very, very dark as light pol­lu­tion from cities and other ar­ti­fi­cial light sources will eas­ily over­power it. And to cap­ture the light you’ll need to set an ex­po­sure that floods your sen­sor with as much light as pos­si­ble dur­ing the time that the shut­ter is open.

The 500 Rule

The ex­po­sure time it­self is lim­ited due to the move­ment of the stars in the sky (or more cor­rectly, the ro­ta­tion of the earth). This is tra­di­tion­ally de­ter­mined by the ‘500 rule’, where you di­vide 500 by the fo­cal length of your lens to cal­cu­late the long­est shut­ter speed you can get away with. So with a 16mm lens that works out at 30 secs (500/16 = 31.25). If you’re us­ing a DX-for­mat Nikon, base this on the ef­fec­tive fo­cal length (EFL) of your lens – so a 10mm lens mul­ti­plied by the 1.5x crop fac­tor gives a 15mm EFL. A more prac­ti­cal method is to start at 20 secs and ad­just un­til you find the long­est ex­po­sure be­fore trail­ing starts.

You’ll also need to set a wide aper­ture to en­able as much light to reach the sen­sor as pos­si­ble – f/2.8 or faster is ideal. But even then, you’ll need to boost the bright­ness of the cap­tured im­age by set­ting an ISO of around 4000.

A shoot of the night sky alone lacks con­text – so some kind of fore­ground in­ter­ested is es­sen­tial. But this in­tro­duces an ad­di­tional prob­lem; the high ISO, nec­es­sary to cap­ture the stars, leads to im­age noise, which will be par­tic­u­larly no­tice­able in the fore­ground. The so­lu­tion is to cap­ture a sec­ond frame for the fore­ground shot at a much lower ISO but with a cor­re­spond­ingly longer shut­ter speed – of­ten sev­eral min­utes long.

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