Astro photography season is just around the corner here in Australia. Every year between February and the end of October photographers all over Australia get excited about photographing the Milky Way at various positions throughout the sky depending on what part of the season they are shooting it. But you do not need to limit yourself to the February – October period to make use of the night sky in your images, and even throughout that season there are other ways to photograph and showcase the stars.
Star trail photography is another good way to get creative with your images for those that are patient enough to try the process. Typically shooting images for star trails requires either a lot of images across the night, or a very long single exposure to capture the Earth’s rotation which gives the impression if the stars spinning. When done correctly the end result is quite impressive with the resulting images representing a passage of time.
There is more to consider than just opening your cameras shutter and hoping to capture decent quality images. Everything about shooting in low light situations is basically the exact opposite many of us learn about landscape photography to get great quality images – shooting as high ISO settings and wide open apertures to be precise. There are many ways to ensure you are getting the best possible quality base images as well as lots of things to consider about location and time planning to begin with before you even start any form of post processing. So let’s take a look at 5 tips for creating and shooting star trail astro photography images and get you on your way to creating great quality shots.
1. Locate the North or South Celestial Pole
The North Celestial Pole and South Celestial Pole are the points in the sky about which all the stars seen from either the Northern Hemisphere or Southern Hemisphere seem to rotate. This rotation is actually caused by the Earth itself spinning rather than the stars. When shooting images for star trails, the circular effect that is so popular comes from positioning your camera facing in the direction of the celestial poles, and specifically in Australia towards the South Celestial Pole. The further towards either east or west you face your camera, the less of a circular rotation effect you will see when you process your images.
Locating either of the celestial poles (depending on which hemisphere you are shooting in) is relatively easy using mobile phone apps such as Photopills. Here in Australia you can find the Southern Celestial Pole by locating the constellation Crux in the night sky. Here is an article with a guide about how to do that.
2. Use the correct equipment and software
Shooting astro photography successfully will require some specific camera equipment and software to be able to produce high quality images. Here is a list of things I recommend –
- Full frame camera that can handle ISO settings of 3200 – 8000 with limited “noise”
- Wide angle (16mm and wider) Lens with a minimum aperture of f/2.8. You can shoot astro images at narrower apertures like f/4 but I recommend at least f/2.8.
- Stable tripod. This is very important. Not all tripods are created equally.
- Remote shutter or camera with in built intervalometer that can handle less than 1 second in between frames.
- In colder conditions some form of lens warmer will be required to prevent the lens fogging up when the “dew point” is reached.
- Spare batteries or even a battery grip that can hold at least 2 batteries.
- Spare memory cards
- Adobe Photoshop (highly recommended as the first choice)
- If you don’t want to use Photoshop then StarStax is the software I would recommend.
As mentioned in the introduction, shooting astro images requires techniques that are generally considered in landscape photography to reduce the overall quality of your images. Shooting at high ISO setting in the range of ISO800-8000 on just about every camera on the market will introduce noise and an overall degradation of image quality into your shots. The key here is to have an acceptable amount of noise and to reduce the impact of this degradation through smart shooting and post processing techniques. By shooting with lenses at f/2.8 or wider you are allowing a lot of light to enter the camera therefore also potentially reducing the need to shoot at really high ISO settings to capture the required amount of light.
A wide angle lens is going to allow you to capture more of your scene, potentially more of the Milky Way (although this is not required for star trails), and also allow you to get closer to your foreground subjects. A stable tripod is fairly obvious and is one of the most overlooked parts of many photographer’s equipment. To continuously capture sharp images you will need a stable base to sit your camera on. Any movement introduced by things like wind will mean your images captured over a long period of time will be useless.
A remote shutter with an intervalometer function, or a camera with this function built in will be needed to continuously trigger the shutter when taking the required exposures. Even the tiniest bit of shake introduced from your finger touching the shutter button will be enough to ruin your chances of capturing sharp images. And when you consider the fact that 100 – 600 images may be required to get the full effect of the star trails, making your life as easy as possible to capture these images just makes sense.
The “dew point” of a lens is the point where the glass becomes colder that the air surrounding it. When you consider that astro season is in the colder months of the year, avoiding the condensation build up that will result in a fogged over lens is very important. There are specific pieces of equipment or even these easy to find gloves that can help you avoid this.
3. Shoot multiple shorter exposures and stack later for best quality
One of the questions I get asked a lot about shooting star trails is whether to shoot a single really long exposure, or to shoot lots of shorter exposures and combine them later. The answer to this for me is always to shoot lots of exposures. There are a few reasons for this which I will list here –
- The longer your exposures, the more likely it is that you will see a degradation of image quality due to “noise”
- Hot pixels form when shooting longer exposures. They will still form when shooting lots of shorter exposures, but you will see far less of them.
- There is less chance of wasting a lot of time when shooting shorter exposures due to external issues not under your control. Things like passing cars, planes flying through the sky or other things that can introduce unwanted light and elements into your images can all be edited out when shooting multiple exposures. If you are shooting a single 2 hour exposure, you will waste a lot of time if that single exposure is impacted on due to external elements.
- You will yield a better quality image when using specific stacking techniques and blend modes when shooting multiple exposures.
- The ability to shoot lots of exposures for the trails and a better quality exposure for the foreground will produce a better overall image. Techniques such as light painting a foreground and shooting at lower ISO and narrower apertures ready to stack in post processing improve overall image quality.
Shooting images for star trails is going to require a lot of patience and prior planning. You can successfully get reasonable images out of a set of 60-90 shots @ 30 seconds / exposure. But the best results are going to come from shooting across a period of at least an hour to an hour and a half and much longer, which means getting 120 shots and upwards (as many as 600 potentially) @ 30 seconds / exposure. Here is an example of the settings I would recommend starting with (obviously this will be very dependent on so many factors) when shooting using any of the current generation full frame cameras from any major manufacturers –
- 30 seconds / exposure
- 16mm and wider focal length
Once you have the images you require, the post processing work begins. As mentioned above I highly recommend using Adobe Photoshop as your one stop shop for all of your astro photography image processing needs. Once you have your image files, importing the images themselves as layers into Photoshop and then changing the blend mode to “lighten” for each of the layers should do most of the ground work for you. Depending on your scene and any of the previously mentioned external factors that could impact on your image, you may need to mask out or remove some layers. When doing this it is important to consider the entire image and whether removing layers or masking out specific parts of any individual layer will create “gaps” in the trails. Even just a single image layer shot at 30 seconds needing to be removed will cause gaps to appear throughout the trails.
Using Adobe Photoshop for this process will also allow you to make far more accurate and better adjustments to either a single layer, or the entire image. You can also mask in a better quality foreground, make far better colour adjustments and more accurate lens corrections etc than when using specific software such as StarStax. But for those that don’t want to outlay the money for Photoshop, StarStax and a combination of other 3rd party editing software can get you a similar result.
4. Don’t forget the foreground
While the stars themselves are what will introduce that feeling of passing time into your images, it is also very important to still consider strong foreground elements just as you would with any other form of landscape photography. When I am shooting for star trails, I will also do my best to get a much better quality foreground image than I would when shooting for the stars at higher ISO and wider aperture settings. For example, when shooting for the stars the recommended starting settings above are ISO3200 and f/2.8 @ 30 seconds. But I typically try to capture the foreground at apertures of f/8 to f/11 at ISO settings as low as ISO400 by using light painting techniques. This may sound strange but I regularly use my iPhone torch to light up the foreground elements for just a few seconds while shooting longer exposures of up to 60 seconds. I will then use that foreground and mask the higher quality image in with the star trails themselves using Adobe Photoshop.
5. Plan your shoot around the right conditions
With any astro photography it is important to plan the time of the year and even time of the month (based on the lunar cycle) to get the best results. During the late Autumn – late Spring months the sky is at it’s darkest. The best times to shoot are around the new moon lunar cycle when there is less ambient light introduced into a scene, although it is still very possible to produce high quality images outside of that period. The factors to consider is where in the sky the moon is, and how full it is. If you can shoot prior to moon rise, or after the moon sets you can still get great images through other times of the lunar cycle. Utilising a moon that is lower in the sky can also assist in lighting the foreground, which can help produce better quality images without the need for light painting.
The typical astro season is when the Milky Way is visible in the sky during the dark hours of the day. But for star trails you do not need the Milky Way in your images, which means you can shoot all year round and still produce high quality, head spinning, time inducing images. You just need the sky to be dark enough, to be cloud free and to be looking in the right direction to get the best quality results.
There are plenty of apps and websites available to help you plan your shoots, and again I highly recommend Photopills for this as most of the information you will require is in this single app. Photopills does not give up to date weather forecasts though, so check your local weather provider and look for nights that are cloud free to plan your next star trail astro photography shoot!
Article Banner Image – Camel Rock Star Trails – 280 images combined shot @ ISO1600 – 30secs – 16mm – f/4 © Kieran Stone