How I Photographed the Milky Way (Part 2)

Welcome to the second part of this guide on how I photographed the Milky Way. If you haven’t read the first part of this guide I would recommend you do so before reading this. In the first part I talk about the equipment you need as well as the other considerations you should make such as location, weather, moon cycle and day length. These tips will give you the best chance of successfully putting into practice what I am going to talk about here in part 2.

In this part I am going to talk about:

  1. The location I chose
  2. Techniques to Shoot the Milky Way
  3. Planning my shoot
  4. Camera settings
  5. What I did on the night

In part 3 I will talk about how I bought all the images I took together, the software I used for that and how I edited the final image in Lightroom and Photoshop.

Choosing My Location

I mentioned in part 1 that it is important to find a dark sky that isn’t ruined by light pollution. In the UK we don’t have too many of those, but one resource you can use is http://www.darkskydiscovery.org.uk/. There are similar sites available for the USA such as www.darksky.org and www.Darksitefinder.com. Being located near London I was keen to see if there was a Milky Way grade dark sky that didn’t involve hours of driving. According to the Dark Sky Discovery website I was in luck, with Iping Common being located just under two hours away. I’ve put the location on Google Maps below:

The location itself was easy to find and has a free car park that you can use. From the car, you can go through the gates and into the common itself. It is a huge area of land, so I’d advise that you arrive while there is still daylight. That way you can scope out the area and find a composition that you like before it gets too dark.

Techniques to Shoot the Milky Way

While researching how to photograph the Milky Way I came across numerous techniques that you can use ranging from a single photograph, to images created from 50 individual frames stacked together.

This list isn’t definitive but covers the most popular techniques I have read about and now tried.

  1. Single Photograph
  2. Composite Photograph
  3. Stacked + Composite Photograph (Recommended)
  4. Panoramic Photograph
Single Photograph

The easiest method of taking a photograph of the Milky Way but one I’ve found gives the least pleasing results. Firstly, when taking a photo of the Milky Way you will need to use a high ISO. But by using a high ISO you will introduce noise into your photograph. I’ve posted a single exposure from my shoot below and you can see a significant amount of colour noise. There are methods you can use in both Photoshop and Lightroom to reduce this noise. However, in my experience, I don’t find this works very well as they also reduce the detail in the Milky Way.

The second issue you will have is the foreground. As you are photographing at night, getting detail in your foreground as well as the Milky Way is difficult to do in one shot. There are a few ways you can get around this. One of these is to select a night with some moon light. The side effect of this is you’ll lose some detail in the Milky Way as the moon light will cause the sky to brighter. Another is to do light painting on your foreground subject. This is cool to do if you have a definite subject like a tree or something close in the foreground. The downside is it might take you a few attempts to get the light coverage right.

Because of the high noise of a single exposure and difficultly with your foreground, I would recommend trying one of the methods below.

Composite Photograph

For simplicity I have split composite photographs up into two parts. The first is a simple composite photograph which contains one photograph of the foreground and one of the Milky Way. The second, which I’ll talk about after this, is a photograph made up of 1 image of the foreground, but a series of stacked photographs of the Milky Way.

A composite photograph removes one of the disadvantages of the single exposure by splitting up the photograph into two parts. This allows you to use the perfect settings for both the foreground and Milky Way. As you are no longer concerned by star trails on your foreground shot, you can use a much longer exposure and a smaller aperture.  This will allow you get to get a much sharper and better exposed foreground.

A few things to mention here:

  • If you want to easily combine the photographs, you need to maintain the same composition for both the foreground and the Milky Way.
  • You can take the foreground shot before the light completely disappears (if you are patient enough!). This allows you more natural light to create a good exposure.

Although this method removes the difficulty of getting a sharp and exposed foreground, it still leaves the issue of a noisy Milky Way. If you fancy something slightly more advanced that will give better results, keep reading.

Stacked + Composite Photograph (Recommended)

This is the method I used to take my photograph of the Milky Way. Before you get scared, this method isn’t that hard and is well worth the effort. It just takes some preparation, planning, and thought before you go out to take the photograph. I’ve posted below a comparison between a single shot and a stacked shot (both with no editing) and you can see a HUGE different in detail and noise between the two.

Single Milky Way exposure vs a stacked Milky Way photograph

The method involves combining the nice foreground shot you would do for a composite photograph, combined with a stacked image of the Milky Way which is made up of 40-50 different types of image. The great thing about this method is that while it reduces the noise in your photograph, it also increases the detail in the Milky Way. As I’ll explain below the process is takes a little bit of planning, but the results are well worth the effort.

The Process

As we’ve already talked about the foreground photograph above, I’ll get right into creating the stack of the Milky Way.

There are several programs that can help you do this depending on what platform you are using. If you are using a Mac I’ve seen people talk about Starry Landscape Stacker which costs £38.99 from the App store. As I am on Windows I opted to use a free program called Deep Sky Stacker which essentially does the same thing. From reading the guides they both appear to work in a similar way, but I am going to focus on Deep Sky Stacker as that is the program I used.

What Deep Sky Stacker does is take a series of different image types and combines them together to reduce noise and improve the detail of your photo.

The different image types are:

  1. Light Frames – These are your actual photographs of the Milky Way. They must be a series of shots taken throughout the night at your chosen location, and with the same composition.
  2. Dark Frames – These are photographs using the exact same settings as your Milky Way ones but are taken with the lens cap on. These frames are used to remove noise associated from long exposures. They must be taken at the same at the same ambient temperature as your light frames so save some time at the end of the shoot to take them.
  3. Bias Frames – Are a series of photographs that are used to remove the electrical noise created by your sensor when you take a photograph. To take a bias frame, you need to put the lens cap on as with the dark frames and use the ISO you used for your light frames (Milky Way photos) as well as the fastest shutter speed your camera will allow (often 1/4000).
  4. Flat Frames – These frames remove vignetting and uneven illumination in your light frames. One of the suggested methods on how to take these is on the DeepSkyStacker It suggests covering the lens (or telescope) with a white T-Shirt and using an external light source such as a torch and use the same ISO as your light frames. Exposure time will be worked out by the camera (use aperture priority).

Once I had figured out the different types of frame I would need to take I began to plan how I would do the shoot on the night. I decided that addition to my photos of the Milky Way I would take dark frames and bias frames as they would both aid in reducing noise in the final image. As I wasn’t using a telescope and knew I could correct vignetting in Lightroom, I opted not to take any flat frames for this image. That could have been a mistake and caused a few issues in the final photograph which I’ll discuss later, but until I’ve tried this technique I can’t say for sure.

 

Planning my Shoot

Before I get into how I approached each frame, I want to quickly go over setting up and some camera settings to take note of:

  • Tripod – As I discussed in Part 1, you absolutely need to be using a sturdy tripod. I am using a Manfrotto Element which is incredibly sturdy as well as light for the price (£89).
  • Focusing – As you are shooting into the dark sky you are not going to be able to use autofocus, so manual focus is a must. There are a few ways to do this. If you have an infinity symbol on your lens you can simply rotate the focusing ring to this to focus to infinity. Another method involves using live view and focusing on a very bright star. You can then fine tune your focus until the star is crisp. I have an infinity symbol on my lens which is generally very accurate, but for astrophotography I noticed it wasn’t quite as crisp as when I used the live view method. So, if you have an infinity symbol or not, I’d advise you to check your focus using live view.
  • Manual Mode – For all the settings you use to take these photographs, you want to be using manual mode. This will allow you to dial in every setting yourself without the camera changing other settings to achieve a neutral exposure. Don’t be alarmed if you see the camera telling you the picture will be under exposed, this will not be the case.
  • Focal Length – For the Milky Way you need to have your lens at the lowest focal length it offers. With a normal kit lens this is typically around 18mm. For the Sigma 17-50mm lens I am using, I would use 17mm.
  • Aperture – Like with the focal length, you need to be using the largest aperture your lens offers. A typical kit lens is around f3.5 at 18mm. For the Sigma 17-50mm lens I am using, the max aperture is f2.8. If you have a lens that opens wider than this such as an f1.8 lens, then I’d suggest that you use that if possible.
  • RAW – I strongly recommend that you take all your photographs in RAW, but for the Milky Way this is even more important. It will give you so much more control in post processing without sacrificing any detail. So, do make sure this is selected in camera.
  • Long Exposure Noise Reduction – I strongly recommend that this is turned off if you are attempting the stacked + composite method. The stacking of the images you take will remove the noise from the final image so there is no need to do this in camera. Another benefit of turning this off is that you won’t have to wait after every exposure for the camera to perform this function. This means you can get through your frames a lot faster.
Getting My Composition

When I turned up at Iping Common, parked up and began to make my way into the common my first thought was “Ok, where is the Milky Way going to be?” That was quite a difficult question to answer when there was still daylight. For me it was even more so as I had never seen it before.

Luckily, I had found an app called SkyView which solved the problem for me. I use the lite version and what it allows you to do is pick a time of day with the calendar and see where things will be in the sky at that time. Using the AR feature I was able to look around the sky at 11:00pm and see exactly where the Milky Way would be. This allowed me to find a nice composition while there was still light and position the Milky Way accordingly. If you can use an app like this I would heavily advise it as you don’t want to be scrambling around in the dark trying to set up your camera. Once you have found your composition you are in it for the long haul. Set up the tripod, camera and get your shutter release ready and sit back and wait for the Milky Way to appear.

Camera Settings

There is no “perfect” setting that will always get you a great photo of the Milky Way. However, there are some rules you should follow which will allow you to get a base for your settings and tweak as required to the conditions. We’ll start with how to capture the foreground before getting into the rule of 500 and how to work out the settings for your light frames.

Foreground

Disclaimer before I discuss this. I screwed up the foreground on the night which is why it is a silhouette in the final photo. I arrived around probably an hour too late to take a naturally lit foreground shot. There was also no real defining feature that I could light paint which left me with a noisy image due to the lack of light. Like I advised above, make sure that you arrive while there is still some daylight, so you can explore the area and get the foreground composition you want.

From a camera settings perspective, you want to treat this as you would a normal landscape photograph. This means using a low ISO, smaller aperture (f4-f8) and a longer shutter speed if the light is fading. The aim here is to capture a detailed foreground to compliment your Milky Way image. 

Rule of 500

One of the key things about astrophotography is that you need to use a long exposure time to allow enough light into the camera. If you use one that is too long however, your camera will begin to pick up the movement in the stars as they move across the sky. These are known as star trails. The rule of 500 is designed to minimise star trails in your photograph allowing you to have sharper stars.

The way the rule works is quite simple:

Exposure time = 500/focal length*

For example, if you are using an 18mm lens on a full frame camera, your ideal exposure time would be 500/18 which gives you an exposure time of 27 seconds. Anymore than this and you will begin to see star trails. The reason I have put an * in the formula above is because if you are using a camera with a crop sensor, your formula with look slightly different:

Exposure time = (500/focal length)/crop factor

For Nikon cameras in the DX line the crop factor is 1.5 and for Canon it is typically 1.6. If you are using a different type of camera you will need to find out its crop factor. For the same example as above using an 18mm lens, you would get (500/18)/1.5 which gives an exposure time of 18.5 seconds. Using this calculation to get your shutter speed is a great starting point for figuring out what your other settings should be.

Light Frame Settings

Not we have worked out the shutter speed using the rule of 500, we need to figure out the rest of the settings we’ll use for our light frames. A good place to start is with your aperture. We want to get as much light into the camera as possible to get the detail from the Milky Way, so start with your aperture as wide as it will go. On a kit lens this will typically be f3.5, however if you have a faster lens with an aperture such as f2.8 use that.

The last element is now to decide that the ISO should be. As you are shooting into the night sky and capturing light that is millions of years old (ok, the millions of years thing doesn’t matter but the concept always blows my mind) you are going need to increase your camera’s sensitivity to light. The best way to figure this out is by trial and error, so take some test shots. Start at ISO 1600 and plug in the rest of the settings and take a few shots. Look at the Milky Way and see if you are capturing enough detail. If the Milky Way is quite faint and you are struggling to make it out, move up to ISO 3200 keeping all other settings the same. Once you are happy with the detail you are getting, you are ready to begin getting your light frames. Don’t worry too much here about noise, the post processing step will remove the majority of this and increase the detail in the final image.

Dark Frame Settings

This is going to be a very short explanation. The only difference between these and your light frames is that these are taken with the lens cap on. It is however extremely important that these are taken directly after your light frames as they need to be taken at the same ambient temperature.

Bias Frame Settings

These are incredibly easy to take and do not need to be taken in the same conditions as light frames. What bias frames do is remove the electrical noise associated with digital cameras from your photo. In order to take bias frames, you need to use the same ISO and aperture as your light frames, but set your camera to its fastest shutter speed. For my Nikon D3400 this was 1/4000 of a second. These are also taken with the lens cap on as with the dark frames.

Flat Frame Settings

Flat frames are designed to remove vignetting and uneven illumination in your images. They are however more important for deep space astrophotography than photographs of the Milky Way. I never took flat frames for my photo but did experience some misalignment of the stars at the edge of the image. I believe this was caused by not applying the lens profile to each light frame before stacking it within DeepSkyStacker. I’ll talk more on this in part 3.

If you do want to experiment with flat frames they are fairly straight forward to take. The AstroBackyard has a great guide which you can follow. 

Shooting the Milky Way

Are you still with me so far? Ok good. There is a lot of detail above but it will all become clear once I break the shoot down. So what did my shoot look like?

Well once I had found a composition I liked I set up the tripod, mounted the camera and waited for it to get dark. It was quite a surreal moment when it was dark enough to see the Milky Way. Although I’d tried to photograph it a few times and failed due to the conditions, this was the first time I had EVER seen it with my own eyes. I can’t describe the feeling of looking up and seeing more stars than you can imagine, but it was quite humbling. 

Test Shots and Focus

The first thing I did was set up my focus. Normally it is advised to manually focus on a bright star by zooming in using live view. I however tried first to set my lens to infinity using the marker and took a few test shots. I started at ISO 1600, f2.8 and a 20 second shutter speed. This didn’t quite give me the detail I wanted from the Milky Way so I increased my ISO 3200 and kept all other settings the same. I did notice however that my stars were not as sharp as I wanted them to be. Using live view I zoomed in on Mars and manually focused the lens until it was sharp. 

Final Settings and Capturing the Milky way

Once I was happy with my settings my shoot ended up as follows:

Light Frames X20

  • 17mm Focal Length
  • ISO 3200
  • f2.8
  • 20 Second Shutter Speed

Dark Frames X20

  • 17mm Focal Length
  • ISO 3200
  • f2.8
  • 20 Second Shutter Speed
  • Lens Cap On

Bias Frames X20

  • 17mm Focal Length
  • ISO 3200
  • f2.8
  • 1/4000 Second Shutter Speed
  • Lens Cap On

So that is how I captured the Milky Way. The final part of this series of posts will talk about the use of the post-processing I did using Lightroom, DeepSkyStacker, and Photoshop to compile the final image. If you found this post useful please share on social media and sign up to my mailing list so I can let you know when new posts are published.

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One Comment

  1. Alf November 5, 2018 at 9:11 pm #

    Very interest and informative, I’ve got to this point myself, but used a different program to stack, so interested to see how Deep Sky stacker works. Looking forward to part 3.

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