Professional photographer Richard Peters gives some of his best tips

In a first of a series of posts by professional photographers, Richard Peters takes us through how he shot the Milky Way.

The recent blog post on my Milky Way shots proved to be very popular and sparked a lot of interest as to exactly how to take images like this. So, Nikon asked if I’d give some tips on how I managed to photograph the galaxy.

Image stacking v single exposure
I researched how best to tackle wide field astrophotography (as apposed to deep sky, where you concentrate on smaller subjects in the sky) with a D-SLR a few weeks ahead of my trip to Maui and almost everything I read and most the images I looked at, involved taking multiple short, low ISO, exposures which included dark and light frames – plus in many cases using a tracking mount. I quickly realised these techniques were not practical for the type of image I was after. So, I did some more research and found some examples of single exposure images, exactly what I was looking for.

So, armed with a D3s and D3 I headed to the middle of the Pacific Ocean to see what I could come up with. I have to admit, after spending the week chasing the Milky Way around the sky I can fully appreciate the difficulty and effort involved with capturing the beauty of the night with great success!

Ultimately, if you do not wish to delve into the world of image stacking or tracking mounts there are five things you need to get good results: correct shutter speed, a fast wide lens, good high ISO, manual focus and, lastly, no light pollution.

1) Shutter speed
First of all, to freeze those stars and the Milky Way in the sky with no trails you need to get a shutter speed that’s long enough to let in the required amount of light, but, short enough to eliminate motion blur. Knowing what the shutter speed is and achieving this result depends on the focal length of the lens, which leads us on to…

2) A fast wide lens
To keep that shutter speed down and to capture as much of the Milky Way as possible you need to go wide, but not just wide, fast and wide. So something like the 14-24mm f2.8 is a natural choice for this type of photography, because not only does that ultra wide field of view allow you to get a lot of the Milky Way in frame, it also lets you get a longer shutter speed before star movement is picked up by the sensor as the stars move across the sky. The reason being, the shorter the focal length the smaller the stars appear on your sensor, so their movement is not as noticeable. As the focal length increases however, the stars get larger on the sensor as you are looking at a smaller part of the sky and so the movement is much more apparent (try looking at the moon with a 28mm lens then a 300mm lens and see how much faster it appears to travel across the frame at 300mm). However, even at 14mm that window of available exposure time to freeze the stars is only 30 seconds; anything longer than that and I could see blur appearing when zooming in to the image. So to include all that sky and give terrestrial foreground interest you really do need to be looking at those fast wide lenses; not only does an ultra wide lens help in terms of what you can fit in the frame, it also helps with getting everything in focus. But more on that a bit later.

3) High ISO
So we know you need a fairly quick shutter speed (quick for a long exposure at least!) and a fast lens. The third ingredient we need is good high ISO to help make full use of all the light let in by that shutter and large aperture. It’s almost pre-programmed in to all of us from the word go when we start our journey with photography that you need to keep your ISO as low as possible for any given shot, so it almost feels unnatural to have to set your ISO as high as you can. This, however, is where the D3s and D3 come into their own. The more you increase that ISO, the more detail you capture in the sky for your given exposure, and even I was amazed at the image quality the D3s was giving me the first time I looked at the back of the LCD screen. Reducing the ISO would result in a far less detailed image, and so I can fully appreciate the need for stacking images on less well ISO equipped D-SLRs. But don’t be afraid to up that ISO as much as you can!

4) Manual Focus
This type of photography requires little to no ambient light, so you need to manually focus your lens to infinity. Make sure autofocus is off and select an ultra wide angle lens – the depth of field offered by these lenses is so great, even at f2.8 you can get the foreground and the sky sharp. Some of the images I took had everything from rocks 20 yards in front of me, to the horizon and the stars sharp with the lens wide open. If you don’t have a lens as wide as that, then you can use a depth of field calculator to work out how close the nearest object needs to be to remain sharp. Or, you could of course just have the distant horizon in the shot with no big foreground details if that works better for you.

5) Dark Skies
Ok, so even once you have all the gear in place, without the right location the success of your images is still going to be limited by the darkness of the sky around you. And although this is the last tip, it is by no means the least important. You need very dark skies for this type of photography as you’ll be amazed how much light the camera can pick up on a long exposure (take a long enough exposure at night and the image will look like it was taken during the day). Just because your eyes can’t see any light, doesn’t mean the camera can’t either and even the glow of a city miles off in the horizon will throw light pollution up in to the air that will drown out the light from the stars – not to mention potentially turn your nice dark sky in to an orange mess. The Hawaiian islands have a 2,500 mile buffer around them making the views of the sky incredible even to the naked eye. And to help even more with that, the island of Maui where I was staying has very few street lights too. But of course heading off to Hawaii to try your hand at this type of photography isn’t very practical, and so the best advice is to just get out as far from your nearest towns as you can and try your best. You’ll certainly be able to get some results wherever you are, but the darker the sky and the further you can get from the nearest town or city the better those results will be. To give yourself an even better chance, give it a go around the time of a new moon, as a full moon will light up the sky and drown out those stars as much as city lights can.

In summary:
You often hear people, myself included, say it’s the person behind the camera that makes the image and equipment is largely irrelevant. And that is in most cases a statement I stand by. But astrophotography of this type with terrestrial elements included is, I think, one time where the right kit is virtually essential. Because if you want good single exposure images of the Milky Way you really do need excellent high ISO coupled with a fast wide lens, as there simply isn’t another way of cheating the amount of light you need to capture within the time frame needed to freeze those stars. Unless that is, you want to get in to the method of aligning multiple exposures, image stacking and carrying a tracking mount with you. But even that has it’s drawbacks with motion blur on the foreground if you want to include any.

But, astrophotography can be very rewarding and, and ISO ranges are keep on improving. And because of that, this type of photography is going to become  accessible than ever before – so next time you have a clear night, get out in the darkness with your tripod and camera, up your ISO, open up your aperture and see what you can come up with!

Images courtesy of Richard Peters