The Basic Guide to Astrophotography

Posted on: 13/08/2017

Astrophotography tips Matt Williams

Most budding photographers assume that taking photos of the stars at night is a difficult and highly-specialised task, but it can be easy with the right settings and gear.

Words & images by photographer and Hema explorer Matt Williams (Matt Williams Photography

There are a couple of things that I absolutely love about getting away from the city for a couple of nights, or even longer. One is the fresh air and the dirt roads. Another is sitting around a nice warm camp fire at the end of the day. But the big one for me is the lack of light pollution and the dark skies! You see, photography isn't just something I do during the day. When the stars come out, I sometimes forget to sleep.

Milky Way Lake Maroon

Equipment

What's awesome about digital photography is that wide field astrophotography is well within most people's reach. So, here are the basic items and why you need them :

Camera

Most DSLR Cameras are more than capable of photographing the starry skies above, however, those that have a full frame sensor and excellent low light capabilities (like the Canon 5Diii and 6D, or the Nikon D600 and D800) will yield better results. That's not to say that you can't get excellent results with crop sensor cameras (Canon 7Dii or Nikon D7100).

Lenses

For wide field astrophotography, you want a lens with a large aperture (small f number) to allow as much light as possible through the lens. This is ideally in the f2.8 range, but you can still get good results with an f4.0 lens. The Milky Way is pretty huge and so a lens with a wide field of view will make it easier to capture as much of it as possible. Something in the 14mm to 16mm range is ideal. The wider field of view will also allow us to use longer shutter speeds to gather more light.

Milky Way dead trees astrophotographyImage: To take in the size and depth of the Milky Way, a lens with a wide field of view and good low-light capabilities is incredibly helpful.

Tripod

A sturdy tripod is essential due to the long exposure times typically associated with astrophotography. You need a solid platform, as most exposures will be in the 15 to 30 second range. Don't skimp here, a good tripod will last a lifetime. Just make sure it's not too heavy that you don't want to carry it!

Headtorch

It's dark out there, so you're going to need a torch. Better yet, get a head torch! That way you will have both hands to work your camera and controls.

Intervalometer

An intervalometer will allow you to trigger your camera remotely without needing to touch the camera. This is particularly important to prevent vibration in the camera. An intervalometer will also allow you to make time-lapse sequences and star trails. Check if your camera has a built-in intervalometer, as they are becoming more common. Some cameras can even be controlled by your smart phone.

Devils Marbles stars
Milky Way compass

 

 

Planning

When it comes to astrophotography, planning is one of the most vital factors which will lead to a successful image being captured. Having an idea of what and where you are going to shoot beforehand is much more beneficial. If you haven't been to a location before, try to visit it in the daytime first, as this saves a lot of time stumbling around in the dark. Knowing where the stars will be, at any given time, will also help you when planning your composition.

This is where your trusty smart phone comes in handy. Apps like PhotoPills and TPE (The Photographer's Ephemeris) are two of the best on the market, and not only provide you with sunrise/sunset times, but also moon phase and the position of the Milky Way.

Star trail astrophotographyImage: Long star trails are composed of many images compressed into one frame.

Finding that dark sky location also requires a fair bit of planning and research. Unless you are lucky enough to live in a remote rural location with super dark night skies, you will probably need to take a drive out somewhere relatively remote in order to photograph the Milky Way. This is a great opportunity to explore new places, so make the most of it and take your swag and camp out! Well, that's what I do anyway! Once you find your location, plan on venturing there some time between the last quarter and first quarter of the moon, ideally during the new moon. This is not a hard rule, but the closer you are to the new moon, the more time you will have during the night with dark, moonless skies.

Another point to consider is the time of the year. The Milky Way (or the best part of it) isn't always visible. In the Southern Hemisphere, the best times to view the core of the Milky Way is from March through to October. Stargazing is also better in the cooler months, as the air is cleaner due to the lack of humidity.

Map Patrol campfire astrophotography

Settings

Put everything in MANUAL. Manual focus. Manual Exposure. Manual ISO. Manual White Balance. Anything that can be in manual, put it in manual. Additionally, make sure you are shooting in RAW too! Raw image files contain more data than JPG files, and therefore allow for greater flexibility in post processing.

Focus

Finding focus is critical in any form of photography. In astrophotography this process is made even harder due to the lack of light to autofocus with. So this is why we must use manual focus. If your camera has it, switch to 'Live View' (viewing your live image onscreen instead of through the viewfinder), then zoom in on a bright star and focus manually until it is a sharp point of light. If you can't focus on a star, you may need to set up a torch at least 100 metres away and focus on that. After you have got your focus 'locked' in, you can then compose your shot. Always make a test shot of the stars with your exposure settings to check your focus. Zoom the LCD all the way into the image review to make sure that the stars look like pinpoints. If they are out-of-focus, circular blobs, re-focus and check again. Once you are happy with the focus, you can use some gaffer tape over the focus ring to avoid any accidental bumps.

Milky Way selfie

Long shutter speeds allow you to collect light over time, the longer you go, the brighter the stars and Milky Way will be. There is a slight hitch however - the earth is rotating! If you leave the shutter open for too long, you will create star trails, which is not desirable for a Milky Way shot. So it’s important to know how long you can expose for before you get star trails. This will vary depending on what focal length lens you use. The longer the focal length, the shorter the exposure, and vice versa.

The 500 Rule 

To ensure you keep your stars sharp while letting in enough light for the shot, you can follow the 500 Rule. Basically, you divide 500 by your true focal length. So, if you are using a camera that is not 'full frame', then you will have to work out your 'crop factor' and multiply your lens focal length by your crop factor. In regards to Canon for instance, the crop factor is 1.6. Therefore, if you are shooting @ 10mm on a crop factor body, your full frame focal length is 16mm (10 x 1.6). You then divide 500 by 16 to give you the maximum amount of time you can keep your shutter open without the stars trailing. 500/16 = 31.25 seconds. You would round this number down to a shutter speed of 30 seconds (you never round up).

In astrophotography, we need as much light to pass through the lens and hit the sensor as possible, so we generally shoot wide open. Set your aperture to the smallest number possible (f2.8, f4). This will depend on the lens you're using.

Uluru night astrophotography

ISO Settings

High ISO's are the key to capturing a bright Milky Way, don't be afraid to push the limits of your camera, this is the only way to capture enough light to create a great image. Start with ISO 3200 and go up or down from there to get the correct exposure. Try to push your camera to the limits of its light gathering capability without compromising quality. Check and re-check your image review, zoom in on the LCD to check focus, review the histogram for exposure information and re-compose your frame often. Once you find an exposure you like, you can usually maintain the same exposure throughout the night.

As a general rule, I start with these settings:

ISO 3200, 30 seconds, f/2.8 as a starting point, this is what I call my 'go to' setting for my 14mm lens. There is a lot more involved to get the perfect exposure, but this will get you a good exposure 90% of the time, and is a good starting point. From there, you can adjust your ISO and shutter speed for the optimum exposure.

Rainbow Valley star trails

Composition

Taking a photo of the night sky is one thing. Being able to tie it to the surrounding landscape in an appealing way is a must if you want your shots to rise above the others. There are quite a few compositional rules in photography, but I find one stands out above all others...your image must have a 'point of interest'. An image without, will not hold your viewers attention for long. It could be something as simple as a tree silhouetted against the starry night sky, or you and a group of friends sitting around the campfire. Oops, I nearly forgot – if you have the horizon in your shot, make sure it's straight!

Last of all, get out there and shoot!

Be prepared for adventure with these navigation products:

Hema HX-1 Navigator
Hema HX-1 Navigator
Hema Explorer App
Hema Explorer App
4WD Map Pack
4WD Map Pack
Australia Road & 4WD Atlas
Australia Road & 4WD Atlas