Sometimes, you just have no time to shoot hundreds of images for creating a star trail photograph. Moreover, you are not entirely into editing and want to avoid all the stacking process. Well you can create a quick star trail image with one single exposure on bulb mode.
There are pros and cons of shooting star trails on bulb mode and also a few important tips for a single exposure star trail.
Night photography is all about long exposures. The exposures may range from as low as a few seconds to a few minutes.
While most night photography shots can be created in a range of one second to thirty seconds exposures, sometimes there is a need to go beyond the shutter speed threshold of 30 seconds.
Enter into the bulb mode. Especially if you want to capture a long enough star trail in your image. Exposures ranging from 5 minutes to 10 minutes should be ideal for getting a cool star trail in your image.
However, before you decide to go for the single exposure star trail, you have to know a few things.
It is going to be a trial and error method until you get to the right exposure.
A fast lens could be your best friend. A wide angle lens will not create long trails as compared to a mid-range lens.
Very long trails will be at a slight risk of overheating your camera sensor.
Before we get in details on the above topics, you are going to need almost the same equipment as you would require for shooting hundreds of images. You can find the list of equipment’s in the link below
Equipment’s required for star trail photography. Now, during your trial and error method, start shooting from low ISO. As you have to beat the noise issue that comes with long exposures.
You can shoot with a wide open aperture, low ISO and for 5 to 10 minutes exposure time to start off with. Check your images before your proceed to the next exposure.
You can turn on long exposure noise reduction ‘On’ but it takes a very long time to finish writing the image on the card, almost the same time as that of the exposure.
Suppose you have an exposure of 10 minutes, it will take approximately another 10 minutes to write the image on your fastest card before your camera is ready to take the next shot. The camera creates a dark frame by itself to reduce noise. Turning on long exposure noise reduction is a pretty effective way of reducing the noise. The only con is, it keeps the camera busy for a long time after every shot before it gets ready to shoot the next.
So, to avoid noise and the delay in writing time and at the same time ensuring you get max light into the lens, a fast lens can be a good friend of yours as you can use it wide open.
One very interesting thing to be taken under consideration while single exposure star trails is that the length of the star trail in your image will be proportional to the focal length of the lens you are using.
For example, if you are using a wide angle lens, say a 14 mm lens, for a 10 minute exposure. The star trails will appear shorter in your image than they will appear on a 35 mm or a 50 mm lens. It is not that the trails are shorter or longer, they are of the same size. It is just in the perspective of the focal length matters.
So if you wish to have long star trails, a mid-range focal length will help you in getting longer trails in perspective.
Another thing to take into consideration is overheating of your camera sensor as it is exposed for a too long time.
As I have told you earlier, to get a considerable star trail effect in your image, you will have to have an exposure of at least 5-10 minutes. For longer trails, a 20 to 30 minutes exposure will be needed. This means your sensor will be exposed for that time. Modern DSLR cameras have sensors protected with overheating mechanism which can take care of such situations, but not all cameras come with it.
Heating up of the sensor also depends upon the ambient temperature. If it is a very cold night, the sensor will heat up less. As the sensor is open for a long time, it is consuming power from the battery. The more power it consumes, it will heat up more. If the temperature outside is cool, the heat will dissipate faster. Also, the more it heats up the more noise it will create in your image.
All said and done, there are not too many reporting’s of a sensor damage due to overheating of the sensor. But keep in mind, the sensor is after all an electronic component and has a life. A 20 minute to 30 minutes long exposure can be easily made with modern DSLR camera. There are photographers who shoot long exposures for as long as 60-70 minutes. The only thing to be worried about is the noise and the quality of the picture.
To be dead sure about getting low noise and maintaining the quality of the image, I would recommend shooting a series of images in a sequence and then stacking images in Adobe Photoshop or Star trail stacking software’s like Starstax or startrails.de
Download our complete guide to shoot star trail images for free
If you are really going to shoot for as long as 30 – 60 minutes, why not be dead sure of the image quality and go for shooting with the image stacking method.
The best way to shoot long exposure star trails is to go for the longest exposure possible in your camera system without any noise issues. And that is possible only with trial and error method.