Our sun is one of about 400 billion stars in our galaxy, the Milky Way. The majestic arc of light formed by the stars in the Milky Way is one of the most wonderous things in nature and with ever more sophisticated cameras it's becoming increasingly straightforward to capture in digital form.
I wanted to give a brief idea of how to acheive a photograph of the stars in the night-sky including, if you wish, the glowing band of the Milky Way.
Knowing a little about the layout of our galaxy will help...
The 400 billion stars are arranged in a kind of disc shape with the majority of them being near the centre. The density of stars decreases towards the edges. Our Solar system lies away from the centre but still some considerable distance from the outer edge. When you look at the arc of the milkyway, you're looking across the plane of the galaxy. Since there are more stars at the centre, that area will be brighter however, you should still be able to make out the band of stars even if you're facing away from galactic centre, it will just be slightly fainter.
Whilst it's useful to have the latest gear and zero light pollution, that's not always possible, especially here in the UK so I'm going to concentrate on what I've done and how I think it's worked (or not) for me.
As with many other types of photography, it's good to have an idea what you want to acheive. Wandering about aimlessly in the middle of the night is NOT the best route to success so here are some more productive things to consider.
The ideal conditions for a milkyway photo shoot are a moonless, windless, cloudless night in an area with no light pollution. The "core" of the milkyway needs to be well above the horizon and (for me) it needs to be more horizontal than vertical. I like to have a decent foreground subject which creates a connection to us here on planet Earth but this is a personal preference. Wanting a foreground subject is another reason I like the milkyway to be in a more horizontal position since it fits into the picture more easily
The moon, even when it's only partially illuminated, is a very bright object in the sky. The light it reflects can massively reduce your ability to distinguish stars against their background - only the brightest stars might be visible while the Milky Way is hidden. Even if you're pointing the camera away from the moon, when there's a lot of dust, moisture or smog in the atmosphere it diffuses the light of the moon across the whole sky creating a blanket of obscurity. I always consider waiting until another day if the moon is above the horizon with anything more than just a tiny area lit like in the image here
Although man-made light pollution tends to be limited to the horizon, it is still greatly diffused by the atmosphere and the resulting glow will easily hide the stars. Unfortunately for UK astro-photographers, the most interesting part of the milkyway (the "core") never comes too far above the horizon. We've got the added disadvantage that we dont have many big open spaces where we can get away from this light pollution. I've found that city lights from over 30 miles away can still affect the outcome of a photo. The good news is it's not impossible to get a decent photo even with a bit of light pollution around. This image was taken in Selsey, pointing East and the light is from Bognor Regis about 6 miles away
It might be obvious to suggest that a lack of cloud is ideal but wisps of cloud are not too much of a problem since they dont usually stick around for too long. If you've set up to take a shot in a windy area, it's possibly going to move your camera about during the time the shutter is open and that's definitely more of an issue. Keeping your camera steady for the duration of the shot is vital. More on this a bit later.
Our sun is one of about 400 billion stars in our galaxy, the Milky Way. The galaxy has a kind of 'disk' shape meaning we see a higher concentration of stars when we look across the disc. This concentration is greatest if we look towards the centre of the galaxy but the milkyway forms a band all the way around the earth. From a photography point of view, the highest concentration of stars (the galactic centre) is the more desirable area to include. It is the brightest area (due to sheer number of stars) but it also has the most obvious colour variations... something that is not immediately obvious to the naked eye. There are only certain times of the year and certain times of night when this galactic core is visible but fortunately, it's position in the sky is very predictable. A team of people have come up with a piece of software called Stellarium (www.stellarium.com) which is capable of simulating what the sky will look like at any time from any location. When I'm planning whether to head out on an astrophoto shoot, I'll check the weather and then Stellarium. It's amazing! Lastly, a personal preference - I like to have something in the foreground of my shots. So long as the foreground doesnt get in the way of the stars, it can work. Even if it's just a good landscape scene it can work but it may be worth considering either photo stacking or compositing to avoid too much noise in the land. Again, I'll mention this a bit further down.
Take a test shot using your widest aperture, a high ISO (I use 6400 on my Nikon D800) and approx 30 seconds shutter speed.
Doing this gives you a feeling for things that might need to change
It's important to zoom into the image on your LCD, otherwise you may not see subtle issues with focusing or star-trailing which would show up in your final photograph.
If you're seeing star-trails where the stars are lines rather than points, that's due to the rotation of the earth... Leaving the shutter open for less time will mean the trails become shorter but naturally you'll reduce the amount of light in the image at the same time. There's a bit of a compromise to make and you'll need to decide how long a trail your final picture can withstand. The "500 rule" is a useful and commonly used rule of thumb. It's a simple calculation which establishes a "sensible" shutter speed for a specific lens focal length. Divide 500 by the full-frame equivalent focal length of your lens to get the maximum number of seconds you should keep the shutter open for if you want to minimize star trails. This is very much a guide and it doesnt mean there'll be no trailing in your resulting shots. Apart from anything else, different stars produce longer/shorter trails depending on their distance from the axis of rotation (usually Polaris, also known as the pole star & the North star). Anyway, this 500 rule is a good guide - you can adjust it if you find it's not good enough for your needs.
Ideally, when shooting, you want to aim for a fast speed, narrow aperture and low ISO but in reality, you'll end up with F2.8 or F3.2, ISO 3200 or 6400 and 25 or 30 seconds. If you find that you're just not getting the milky-way coming out in your shots, it's possibly because the area you're in is suffering from a bit of light pollution. Dark skies always seem to be in the most remote places - especially in the UK but you may find some darkness at the coast or in one of the national parks. The other reason your milkyway may not be showing up properly is that your ISO sensitivity may be too low... increasing the ISO will result in more sensor noise so I'd suggest this is where you might like to consider stacking your photos. At this stage, that's quite easy... you simply take several shots one after the other without moving the camera. You'll combine the shots together in photoshop and take an average from all of the shots - hopefully the noise in one shot will be cancelled out by a lack of noise in the other shots. More about this in the "post-processing" section later.
Stacking If you're getting too much noise in your pictures and you can't lengthen your shutter speed or widen the aperture on your lens then you may want to consider combining several (noisy) shots. First and foremost, you'll need to have a number of very similar shots in order to do this. Life is easier when you have no foreground to consider but even with a foreground, it's fairly straightforward. Back on the computer, you can open up all the photos together, mask out the foreground and align the images. Photoshop is pretty good at doing this automatically but there are manual methods too if you need them. Once aligned, combine all the layers into a smart object and stack them using the "median" method. and then combine them back on the computer in such a way that the noise is "averaged out". There is a step by step process involved and rather than me go into detail here, I recommend watching Ian Norman's YouTube video on the subject by clicking here.
Light Leaks Many cameras have a method of shading the viewfinder to prevent light leaking in. If you dont have such a device, it's worth considering getting or perhaps making one. During long exposures, even the slightest light from behind the camera can get in and reduce the contrast of your image or produce random flares of light. Sometimes, these light leaks can be so subtle you dont notice them until you're back on the computer and it's too late so it's worth making the closing of your viewfinder part of your astro-workflow.
Condensation One of the most frustrating things to contend with is condensation forming on the lens. It occurs when humid air comes into contact with the cold glass of your lens. Once it's there, it's tricky to get rid of and it reforms very quickly so the best option is to prevent it in the first place... a lens hood is a good option but you can also get devices that can warm your lens slightly.
These "dew heaters" require a powersupply and cables which make them more cumbersome and another potential point of failure but they are also reusable, easy to attach/remove, arguably more reliable and perhaps more environmentally friendly too.
If you prefer a slightly more DIY approach, you can use flexible hand warmers such as the ones I've linked to here
I've done a fair amount of astro-photography now. I'm particularly keen on photographing the milky way along with a foreground subject of some sort.
There are limited opportunities to do it in the UK so when I see the skies are clear and there's no moon, I start wracking my brain trying to think of new places to go where there's an interesting foreground subject and a lack of light pollution.
Scouting locations during the day has become a bit of an obsession!
Some places turn out to be less photographically productive due to light pollution - we get so much of it here in Sussex despite being close to The South Downs National Park. Nonetheless, I've created some photos I've been pleased with and for which I've had good feedback.
I thought I'd give some details here on what I do to get my shots but feel free to ignore all the text and just look at the pictures.
At this stage I should mention that I can and do create prints of my images so if you'd like one, please let me know. Even one offs are easy to produce.
So... lets start with the gear I use. This isn't everything, just the basics. Maybe I'll go into the more advanced stuff if I get good feedback from this post! :-)
Camera:- I use a Nikon D800. I have also got a Canon 550D which can produce some good stuff but the images can be noisier than the D800. I dont think theres much of a difference between the manufacturers, and these days I don't think there's too much of an advantage to having a full frame camera, other than the possible extended field of view.
I thought I'd write down some of the things I've learned while doing this stuff so that others might benefit but since it's such a big subject, I thought it was prudent to create a page dedicated to the subject rather than filling this blog page with too much waffle that some might find uninteresting.
So, if you want to read more about my astrophotography and milkyway adventures, click here. If you just want to look at a selection of my night-time pictures, click here and you'll be sent to my gallery page.