The stars have always fascinated us and it is a fascination has been hard-wired into our brains, I reckon. Every little kid, at some time in his/her formative stage would have dreamt of being an astronaut – with a pilot and a train engineer following sequentially in the pecking order. It is the years of conditioning in our urban cities, with their polluted skies, that make us forget the existence of an unexplored universe beyond the haze. A fascination that re-emerges when you are out in any open and clear part of the country while travelling.
I do look out for any chance to photography the night sky while I travel but these opportunities have been few and far between. And while one does get a few chances to attempt star-tails, seeing the Milky Way has been something of a rarity for me.
The image below is one of my recent attempts at capturing our majestic galaxy. I must admit that there were quite a few areas that were wanting in execution but I am using this image to put down simple steps to follow to get this right.
- A dark and clear sky – this is mandatory. Ideally should be free of clouds (or if there are, they shouldn’t be in the frame). Moon is one bright object that can ruin the sighting of the Milky Way – so, ideally, you are looking for a moon-less sky (a new moon night is perfect but before moon-rise would be great as well).
- In the Northern Hemisphere, the period between February and September is the best time to see the Milky Way. Usually, you will find the subject in the southern half of the sky, rising from the east. Best would be to use any app like SkyView to locate the Milky Way and track its movement over time.
- You will need a good DLSR camera (I use the Nikon D500 though a full-frame body would be preferable), a fast wide-angle lens (I use the Tamron 11-16 f/2.8) and a sturdy tripod (this is mandatory as these images will require a long exposure and any wind-induced shake would ruin the image).
- Camera settings:-
- (a) Mode – Check your camera to locate which Mode the ‘bulb’ shutter setting is available. On the D500, this was in the Manual ‘M’ mode and that’s what I switched to.
- (b) Aperture – a wide-open aperture setting to ensure that you are capturing the max. possible light that the lens allows.
- (c) Focus – in real dark conditions there would be insufficient light to acquire focus. What I did was to try and get the lens to focus at ‘infinity’ and switched the camera to a manual focus so that this gets fixed and doesn’t change inadvertently.
- (d) ISO – While many recommend that you start with a high-ISO (like 1600 or 3200) to ensure that you can maximise the sensor sensitivity to light, I was a little bit too conservative on this (I had dialled in a 400 ISO for the above photo) and maybe that is something I should try another time.
- (e) Shutter speed – The ‘bulb’ mode allows an exposure for as long as the shutter is pressed down. In the Manual mode you scroll your selector wheel all the way to the end of the shutter speeds. After 25″ (25 seconds) or 30″, it will show “bulb” or simply the letter “b” on some cameras. Now you’re in bulb mode. This means the camera will keep taking a picture until your finger comes off the shutter button. In the D500, in the ‘bulb’ mode, once you have kept the shutter pressed for a few seconds (and have released the shutter), one can take the finger off the shutter and then go back and press it to close the shutter after the adequate exposure has been achieved. Ideally, a remote trigger is recommended to avoid any unwanted shake introduced by the manual action of releasing and closing the shutter.
- (f) White Balance – If you are shooting in RAW, you can always adjust this in post-processing. But it helps to keep in mind that the colour temperature of the Milky Way is about 4840˚K, so setting the White Balance to around this number would ensure that you will get a realistic view of what the final image would be like.
- Now that we have the basics set-up, how does one calculate the optimal shutter-speed (and thereby the exposure). The 600 rule comes to our help here – it states that in order to eliminate star trails (because of the rotation of the earth) the exposure time in seconds should be 600 divided by the effective focal length of the lens being used. In the above instance, I was using a 11mm lens on a crop-sensor body – that is a factor of 1.5 to adjust for, so I was effectively at 17mm. So, I needed a shutter-speed of 600/17 ~ 35 seconds to get this absolutely right.
- With all the elements now in place, it is time to compose your shot. There’s no specific recommendation here except to remind you that you can create a sense of depth by introducing an interesting foreground. Ideally, pick an object of interest that is immobile – hills or mountains, rock formations, buildings or even a person. With some foreground, like trees, remember that over a 30+ second exposure there would be movement of leaves in the wind that would introduce an unwanted blur that might ruin the image. Also, depending on the strength of ambient light, you might need to externally illuminate the foreground (also called ‘Light Painting’) to ensure that there is adequate lighting on the foreground to capture it in your frame optimally. This could take some experimenting with to get right.
- Now, it is time to expose your image and see the output. It is quite likely that you may not nail all of these on your first shot, adjust the areas (focus, composition, etc) that you are not satisfied over a few attempts. If the exposure isn’t looking “correct” you will have to troubleshoot and work from there. The main issues on exposure could be (a) too much noise (b) over-exposure or (c) under-exposure. Decrease the ISO if the shot is looking excessively noisy. If you feel that your shot is overexposed, check for ambient light pollution; decrease shutter speed; stop down the lens; decrease ISO; or even dial-down exposure compensation. On the other hand, if you think it is underexposed, make sure you’re using the widest aperture on your lens; increase shutter speed (but beware of star trails forming); increase ISO; dial-up exposure compensation.
So, there it is. All the stuff I have learnt from my botched attempts at capturing the magnificence of our galaxy. I am hoping that one of these days, I will get them all right.
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Reblogged this on Wolf's Birding and Bonsai Blog.
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