How to Shoot an Astro Timelapse
Milky Way season is the best time to learn how to plan and shoot an astrophotography timelapse, capturing the majestic galactic core in motion!
Although PetaPixel has published a detailed complete guide on astrophotography before, it is still better to make some quick notes on the very basics before proceeding further. Let’s make sure we’re all on the same page.
The Visibility of the Milky Way
One of the most popular points of interest in the night sky is of course the amazing Milky Way Galaxy Core! It is simply spectacular to watch it with your own naked eyes, and a joy to capture it on camera.
However, due to the Earth’s journey around the Sun, it is not always “visible” to us. Obviously, it is there all the time, but during the months from November to January (for Southern Hemisphere) or February (for Northern Hemisphere), it cannot be seen because its relative position above the horizon occurs during daylight. So basically, the Milky Way Season, if I’m allowed to use that term, happens from mid-February to late October each year for both hemispheres.
Each month after February, the Milky Way becomes again visible, which practically means that during nighttime it rises above horizon level for a longer period allowing us to plan an astro timelapse shoot! But where should you look in the night sky?
At the beginning of the Milky Way season and for the northern hemisphere, the galactic core can be first seen to the southeast moving slightly to the south as it rises in the sky.
In the middle of the season, around May, it can be seen in the south, and as we move to the end of the season, September and October, it can be seen more in the southwest.
For the southern hemisphere, it is somehow the opposite, which means that the Milky Way will be visible to the southwest at the beginning of the season, and later be more toward the southeast.
Thankfully, there is a useful free tool to help us check when the Milky Way will be visible on a specific date and location. This tool is an app called Stellarium and through it, we can check how the night sky will look at any given time in any place in the world using our smartphones or computers.
Through this application, we can also find other objects of the night sky, the location of the Moon, and many other helpful pieces of information that can assist us in preparing for a night sky astro timelapse.
The Problem of Light Pollution
We are used to having artificial lighting after the sun sets in our cities, as it makes us feel more secure. But the problem with that is the lights in the cities (i.e. on the roads) and even on our houses are producing a “pollution” that affects our visibility towards the night sky. This is called Light Pollution and there is a scale measuring it, called Bortle Scale.
It is worth mentioning that light pollution not only blocks our view of the night sky, but it also has serious consequences on our health and affects the whole ecosystem. More information about light pollution can be found in International Dark Sky Association – International Dark-Sky Association.
Light pollution usually is captured in our images as a warm orange tint close to the horizon like in the example below:
In addition to artificial light pollution, there is something else that can affect our visibility to the night sky: the Moon.
As Moon is a celestial object that has its own orbit around Earth, it has phases in which it reflects more or less light toward Earth.
To enjoy the night sky in all its glory, the Moon has to be in the new Moon phase, which literally translates to 0% reflection of light illumination toward Earth.
An example of how moonlight can ruin our visibility of the night sky, even when it’s in the first quarter can be seen below:
To conclude, in order to see and capture the night sky and the stars in all their glory, we need to work out a specific date based on the Moon’s phase, but we also need a location free of artificial light pollution.
Let’s see how we can find a potentially good location before leaving home.
Preparation is the Key
As technology advances almost every day, we are thankful to have amazing tools that can help us prepare for an outdoor photo shoot from our computers. And most importantly, most of these tools are free to use.
Light Pollution Maps
The first thing to do is to find the light pollution levels in a specific location/area/city/country. There are two helpful web-based tools to do this:
With these tools, we can search any location or area around the world to find a good, light pollution-free location for our astro timelapse sequence.
Google Earth
After deciding in which location we plan to shoot our timelapse we must ensure that it is safe as we will be working with minimal or no lights at all. This means that especially if we have never visited that location before, we have to be 100% certain that there are no immediate dangers to our safety. There is nothing worth more than our lives, especially a photo or a video, so we must check if there are any sudden cliffs or even any wild animals in the area that may hurt us.
Google Earth is a helpful tool to check the surrounding area for cliffs and other dangerous landscape features.
Regarding wild animals, a phone call to the local forest or park office will provide helpful information on this, or you can simply ask local people in the area.
In any case, it is strongly advised to reach the shooting location during the daytime in order to familiarize yourself with your surroundings and check everything with your own eyes before the light fades out.
Did you know that Google Earth can also show a relatively simple representation of how the Milky Way galaxy core will look in the selected location?
Personal Preparation
Lastly, after ensuring that everything is checked, it is time to prepare ourselves for the shooting.
The most important thing is to be fresh as we will spend many hours out in the field during the night, as also including the extra time of driving to the location. This means a good rest is advised prior to the night sky timelapse shooting.
If the location would be in higher altitudes, for example in the mountains, warm clothing is a must to protect us from the cold or the winds. As temperatures will be lower than those in the city no matter the season, batteries could be affected so make sure to have at least one or two fully charged spares with you.
On the contrary, if the shooting is going to take place in a hot and humid environment, then some bug repellent could be important.
In any case, when working in low light conditions, a headlamp with red light* is also a very helpful and inexpensive accessory that will allow both your hands to be free when working in the dark.
Note: Red light doesn’t affect our night vision and that’s why it is advised to use one out in the field.
Lastly, make sure that your phone is fully charged in case something happens and assistance is required, or if you already are aware that there is no signal reception in the area, having a GPS emergency beacon could save your life.
A good checklist of personal items that should be in your backpack is the following:
- Warm (and dry) clothes
- Wind jacket
- Bug repellent
- Snacks and hot drinks (tea, coffee, etc.)
- Headlamp with red light
- Fully charged mobile phone/GPS emergency beacon
Required Camera Gear
It is now time to mention the required camera gear to work with.
Camera
The most basic requirement for an astro timelapse shooting is of course a camera in which manual exposure settings can be applied. No matter if it is entry-level or not, DSLR or mirrorless, as long as it can be properly adjusted for the requirements of this project, it should work perfectly.
Lens
This is the other most basic item that is needed. Although even a kit lens could work relatively well in theory, a fast lens with a big aperture (and low f-number) is ideal to allow more light to enter the camera sensor.
However, depending on the focal length of the lens, the result will be totally different but that will be analyzed in the next section.
Light Pollution Filter
While we already mentioned that a location with minimal or zero levels of light pollution is ideal for this type of shooting, still it is not always so easy to find one within your reach.
Even if you visit a relatively close mountain that indeed offers low levels of light pollution, some traces could still be seen, especially if a big city is close by.
In this case, using a light pollution filter is advised to eliminate the last traces of visible light pollution near the horizon.
Tripod
A good and sturdy tripod is a must-have for this type of shooting, as we will be dealing with extended shutter times for a long period of shooting and we have to be certain that the camera is absolutely still so to capture sharp images for the whole sequence.
Intervalometer
If the camera doesn’t provide an internal menu option that allows us to shoot timelapses, then a separate external tool called an intervalometer is required.
Lens Focal Length
It was mentioned before that depending on the selected lens focal length, the end result will be different. But what does that mean and look like, exactly?
If an ultra-wide-angle lens is going to be used, around 14-18mm on a full-frame camera, the effect it will have is that the Milky Way galaxy will look taller and thinner in the frame, and it will move more slowly across the screen in the final exported video.
This was shot at 16mm:
As the focal length is getting bigger, again in full frame >20mm, the MW galaxy will start to look thicker but shorter in the frame, while also “moving” faster across the screen.
This was shot at 50mm:
As we can see from the demo samples, the lens selection has an immediate impact on both the artistic result, as also in the exposure settings that will be used.
Exposure Settings
In astrophotography when we want to capture pinpoint stars without trails, we must make sure to find the proper exposure settings that will allow enough light to reach the camera sensor but at the same time have a shutter speed that will allow us to capture pinpoint stars.
In the old days, when cameras were around 10 to 12 megapixels there was the famous 500 Rule, in which you would divide 500 with the selected focal length to find the ideal shutter speed.
Well, since then a lot has changed and even entry-level camera models have a resolution of more than 20 megapixels, which practically means that this old rule cannot be applied anymore with acceptable results.
The new rule that applies to high-resolution sensors is called NPF, and there are free NPF calculators out there that you can use to easily figure out your optimal settings.
However, there is a small advantage when shooting astro timelapses and that is that even if we use a slightly increased shutter speed, the effect will not be directly visible to the end result, and it will actually make the motion look more fluid.
For example, if the NPF calculator proposes a shutter speed of 13 seconds for pin-point stars, even if we use a shutter of 15 or even 17 seconds, there will not be any trails visible in the rendered video.
Long Exposure Noise Reduction
There is a camera setting that can also be crucial to achieving a great-looking result — if it is available and enabled, it can create unnecessary delays in the shooting process. The setting is usually called something like “Long Exposure Noise Reduction”.
When this option is enabled and if an exposure longer than 1 second is selected, after the frame is captured, the camera creates a second frame with the same exposure settings but with the shutter closed. This frame is called a dark frame and the camera uses it to subtract any visible noise produced by the sensor from the original frame.
Although this might be a useful option for stills, for timelapse shoots, it can create serious gaps between frames resulting in a not-so-fluid motion in the produced clip. For example, if a shutter speed of 10 seconds is selected, after the exposure finishes, the camera will require another 10 seconds before showing the captured frame on the back LCD.
Interval and Frames
Since we found the ideal shutter speed and exposure settings overall for our gear, it is time to calculate the proper interval for the actual shooting and there are some things that might create missing frames, which can create a bad result.
In addition to the shutter speed that must be included in the interval, we also have to include the required time to clear the buffer memory.
The last generation models of all camera makers have reached a level where the camera can capture a huge amount of photos without even hitting the limit of its buffer memory, but there are some older models that need at least 1 second to transfer the recorded image to the memory card.
Memory cards also play a huge factor in this, so in case a memory card with low writing speed is selected, then you first need to find out how much time it takes to record the shot.
Regarding the required amount of frames, that depends on the desired length of the rendered video clip. Photographers may opt for at least 10 seconds of footage, so in case you plan to export at 24fps, then at least 240 frames are required.
It is important to once again note at this point how much time the overall shooting will take, based on the fact that each frame usually takes around 20 seconds (including what was mentioned about interval).
Creating Foreground Interest
As in astrophotography and no matter how beautiful and impressive the night sky might be, the interest is created by the foreground, so be sure to include a subject that can attract the viewers’ eyes or lead them toward the night sky.
One thing to consider is the distance between the camera and the subject, as in most cases we are working with the aperture wide open and the lens is usually focused on infinity.
This means that in case a lens with a focal length between 20-35mm is being used in conjunction with an aperture of f/1.4 to f/2.0, and the distance between the camera and the subject is relatively close, you will end up with a very soft or even unfocused foreground.
Always keep in mind that the relative distance between the camera and the subject is crucial for this type of shooting.
Motion Makes the Difference
Although a static timelapse sequence will look really great, imagine how drastically that particular scene could change if you add motion to it, and by motion, I mean dynamic motion which translates to a camera that is not static.
That motion can happen in one axis (slide), two axes (pan and slide), or three axes (pan, slide, and tilt).
Note: There are now 4-axis motion control systems where the 4th axis controls either the zoom of a lens or its focus ring.
There are many tools that can help you create this motion, from a simple star tracker or a simple motorized slider to some very expensive dedicated motion control systems.
On some occasions, even a gimbal can be programmed to shoot a 2-axis timelapse sequence.
However, it is very important to note that when adding another piece of gear to the shooting setup, and especially if it is moving, there are some things to be considered that will ensure a better end result.
The first one is to be certain that while the motion control system is moving, the center of gravity remains constant, ensuring that your camera will not fall down, and of course that the whole setup is sturdy enough so to have sharp images.
That means that if the motion control system is not on the ground, your tripod or tripods (you will need two if the slider platform is longer than 1m in length) are very sturdy and can accept the overall payload.
The other thing to consider has to do with exposure.
When the motion control system changes its position frame after frame (this programmed motion is called move-shoot-move), it creates micromotion from the weight of the camera attached to the platform, and it requires a moment after it stops its movement to settle.
That practically means that you must include that extra time to become idle in your interval settings.
For example, if my exposure settings have a shutter speed of 15 seconds, I have to include at least 1 or 2 seconds to be certain that the motion has ended, and the camera is stable.
A small note here: It is also possible to add digital motion (usually panning) in post-processing. This of course cannot replace the effect of an actual motion that was created in the field, but it can honestly really save the day on occasions when you cannot shoot with a dedicated motion control system.
The logic behind this is that most cameras record stills with a resolution of at least 24 megapixels which translates to something around 6000×4000 pixels.
That means that even if you export your final video in 4k UHD (3840×2160), you still have a lot of resolution to work with.
Practically you can add simple zoom-in and zoom-out effects and slight panning motion from left to right or vice versa, or up and down on most video editing software and on dedicated timelapse editing applications.
Conclusion
This guide was a long read but I hope that we have covered almost all aspects of an astro timelapse shooting. Hope that everything is now set for you to go out in the field and start shooting!
Image credits: All photos, unless otherwise noted, by Christophe Anagnostopoulos.
