Anyone familiar with basic camera settings like shutter speed, ISO, and aperture (f/ratio) is more than capable of capturing decent astrophotos like constellations, meteors, planetary and lunar alignments, Iridium flares, ISS flybys, star trails, and even the Milky Way. In most cases, only a DSLR-on-a-tripod setup is required. In some instances, however, an additional accessory called a cable release becomes a necessity, and without it, it is simply impossible to take advantage of the most useful feature of a DSLR camera: the bulb setting. This article explains why such an accessory is important and how you can build one (for Canon DSLRs) that performs technically the same function, equally as reliable, but costs just a fraction of the commercially available counterpart (and the best part is, you actually built it yourself!).
WARNING: I will not be responsible for any damage caused to your equipment. Follow instructions at your own risk!
Can I just use the camera’s timer?
Short answer is NO. To completely eliminate motion blur, you need to keep the camera steady during exposure. Pressing the shutter directly would not work since it introduces undesired movement which could affect the image, especially during long exposure photography. A quick solution to this problem is by using the time-delay function of your camera to “press” or “activate” the shutter automatically after a predefined time (consult the manual). Unfortunately, even if used with the longest allowable shutter speed, the time-delay function can only keep the shutter open for around 30 seconds for most DSLRs — too short for astrophotography, where exposures of a few minutes to a couple of hours is not uncommon. This is where a cable release becomes a necessity.
A cable release is simply a device (in the form of a cable) used to remotely control the camera’s shutter. Its one end connects to a camera through the cable release port, while the other end has a button or a switch that can keep the shutter open for as long as it is ‘pressed’. It is used primarily to take advantage of what is called the bulb setting. Under this setting, the camera’s shutter can be manually controlled, thus, exposures ranging from a few minutes to a few hours is now possible. With this accessory, you can take pictures without really touching the camera’s body (thus, undesired movement or vibrations caused by pressing the shutter could be completely eliminated).
The DIY Cable Release
For this do-it-yourself (DIY) project, you only need the following:
- a length of cable with 2 leads (that is, there must be 2 wires inside)
- a 2.5 mm earphone jack
- any type of switch
You will also need a pair of scissors, some electrical tape, and a soldering iron (optional). All components cost less than a dollar (approx 43 php), and may be assembled in less than an hour.
Step 1: Get the materials ready. Basically what you need to do is to connect the switch on one end, and the earphone jack on the other end. You may use a pair of scissors to expose the copper wires/leads.
Step 2: Connect one end of the wire to switch as shown in the picture. The cable has two leads (or wires). The switch should be able to ‘short’ the two wires when the switch is turned on (or the circuit is closed). The purpose of the switch is to momentarily create a ‘bridge’ or a ‘connection’ between the two wires. Once a connection is made, the camera senses it and immediately opens the shutter. Thus, any type of switch may be used for this purpose. Set the switch to ‘off’ position (circuit is open) before making the connection.
Step 3: Connect the other end of the wire to the earphone jack as shown in the picture. Again, the cable has two leads (or wires). The earphone jack has 3 connection points. We are only interested in the “center (core) pin” and the “outer pin”. One of the wires must be connected to the center pin, while the other wire must be connected to the outer pin. Note that one of the pins (the one that is between the “center pin” and the “outer pin”) is left intentionally unconnected as it will be used for future improvement of the DIY cable release (will not be discussed yet in this DIY project, stay tuned for new DIY posts).
Step 4: Use electrical tape to insulate all electrical connections.
Step 5: Locate the cable release port of your camera. In this particular model (Canon 450D), the port is located between the ‘video out’ port and the ‘USB’ port (consult the manual).
Step 6: Connect the cable release to the camera through the cable release port.
Step 7: Set the camera to manual mode and activate the ‘bulb’ setting (consult you manual on how it is done). Test the DIY cable release by turning the switch on (circuit is closed). If successful, the camera should readily respond. It will raise the shutter (keep it open) for as long as the switch is set to “on” position.
Enjoy the DIY cable release and happy shooting!
For featured photos, click here.
For tutorials on how to get started with astrophotography, click here.
For DIY astronomy projects useful for astrophotography, click here.
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© Anthony Urbano (Manila, Philippines)