Canon is once again expanding the horizons of astrophotography with the arrival of the Canon EOS Ra, a special edition of the acclaimed full-frame mirrorless Canon EOS R that is optimised for deep-sky imaging.
With its full-frame 30.3 megapixel Dual Pixel CMOS AF sensor, high ISO performance and low-light autofocus, the Canon EOS Ra sets a new standard for night sky imaging.
Here, Canon professional imaging specialist and passionate astrophotographer Matteo La Torre offers some insights into the advantages its advanced features offer to astrophotographers.
Like the Canon EOS 20Da and Canon EOS 60Da before it, the Canon EOS Ra is more sensitive to infrared light thanks to a modified optical low-pass filter that sits in front of its imaging sensor.
"The filter has been designed so that not only does it allow the passage of electromagnetic radiation within the visible spectrum, it also allows the transmission of a particular light emission at the near-infrared wavelength of 656nm [nanometers]," explains Matteo.
"This specific wavelength is the result of the radiation of ionized hydrogen, called H-alpha, which is emitted by deep-sky objects such as Messier 42 (the Orion Nebula), the Rosette Nebula, the Veil Nebula, NGC 6820, LBN 331 and IC 434 (the Horsehead Nebula)."
Compared with a standard EOS camera, four times more light at 656nm is transmitted through the Canon EOS Ra's low-pass filter. This allows the distinct red tones of H-alpha emission nebulae to be rendered with incredible colour and clarity.
Like its astrophotography forebears, the Canon EOS Ra can be used like an ordinary camera. As a consequence of its higher sensitivity to some infrared frequencies, however, some colours will look strange – it will capture colours in flowers and some man-made fibres, for example, that the unaided eye doesn't detect. Note also that the Canon EOS Ra is not simply an infrared camera and is not designed for scientific or creative infrared photography.
As the world’s first full-frame mirrorless camera developed for astrophotography, the Canon EOS Ra offers a number of benefits over a DSLR.
"This camera's light weight combined with the reduced vibrations from having no internal mirror bring an improved performance when attached to a motorised telescope," says Matteo. A motorised mount enables the camera to track the night sky as the Earth rotates, preventing stars being recorded as streaks.
"The attachment itself is less complex than with a DSLR, thanks to the short flange distance and large diameter mount of the EOS R System," says Matteo.
"You can attach the EOS Ra directly to the eyepiece holder of the telescope via a T2-RF adapter ring or by using one of the EF-EOS R mount adapters and a T2-EF ring.
"Alternatively, you can fit a lens to the EOS Ra and mount this on the telescope using a static or tilting 'piggyback' device, which enables the telescope and camera lens to be aligned and track the sky in parallel."
"Many different lenses are suitable for astrophotography," adds Matteo, "although my advice would be to use an L-series lens with a maximum aperture in the region of f/1.2 to f/4.
"You might think you need to select a very long focal length, but this is not the case. Fisheye and wide-angle lenses can be used to capture meteor showers or to record the Milky Way and a landscape in the same frame. An everyday, standard zoom such as the Canon RF 24-105mm F4L IS USM or EF 24-105mm f/4L IS II USM (with mount adapter) is also more than up to the task and can deliver satisfying results. Just make sure you use the lens hood to prevent stray light hitting the front element."
At the heart of the Canon EOS Ra is a full-frame 30.3 megapixel CMOS sensor. Because a full-frame sensor is physically larger than a cropped sensor with the same pixel count, a full-frame camera can capture more light, resulting in an improved signal-to-noise ratio.
"The Canon EOS Ra is the best EOS camera ever conceived for capturing the landscape and the night sky," says Matteo. "The opportunity to work in 14-bit RAW and the flexibility offered by the native sensitivity range of ISO100 to 40,000 certainly outperforms the great results we have seen from the EOS 20Da and EOS 60Da."
All aspects of the Canon EOS Ra's image processing are taken care of by the latest DIGIC 8 chip. "DIGIC 8 offers enhanced noise reduction, distinguishing stars from noise with precision and at a faster computational speed," explains Matteo.
"This gives greater freedom to select an ISO based on the feature you want to capture, the specifications of the telescope being used, the precision of the targeting system and the environmental conditions, such as the temperature. A build-up of heat in the sensor increases noise; in-camera functions such as noise reduction for long exposures and high ISO are obviously beneficial, but it's also important to keep the camera cool." That's one reason the Canon EOS R makes such a great foundation for an astrophotography camera: its magnesium alloy body is very efficient at dispersing heat, meaning less heat noise at long exposures.
There are no hard-and-fast rules, but Matteo has one tip based on his personal experience: "Waiting some time between each shot – perhaps even up to a few minutes, depending on the exposure time – can help to avoid excessive noise."
As well as its role in noise reduction, the advanced DIGIC 8 processor enables 4K video recording. In addition to recording internally to a memory card, footage can be output in 10-bit to an external recorder via HDMI, giving you another creative way to capture the sky at night. It's particularly good for planetary imaging.
Another useful feature, not only in terms of autofocus but also for monitoring, is the Canon EOS Ra's Vari-angle touchscreen. This can be rotated and tilted to give the optimum clear view when shooting from the awkward angles often required for astrophotography.
Manual focusing has traditionally been the best option for shooting the stars, and the Canon EOS Ra offers a new 30x focus magnification option for additional precision when using a telescope. Its highly sensitive Dual Pixel CMOS AF system also makes low-light autofocus a reality.
"The camera's extreme autofocus sensitivity down to -6EV means that the AF system is very responsive," says Matteo. "When shooting through a wide-angle or fisheye lens, it can also be useful to activate the Touch Shutter function."
This feature reduces the risk of camera shake caused by pressing the shutter release – it requires only the lightest touch to take the shot, so it's a great alternative to a remote shutter control. If you prefer the latter, though, read on...
There are a number of ways to trigger the Canon EOS Ra remotely for sharper results. For example, the camera is compatible with the TC-80N3 Timer Remote Control (via an RA-E3 Remote Control Adapter), which offers long exposure and interval shooting.
Alternatively, the Canon EOS Ra can be tethered directly to a PC or Mac via Wi-Fi or USB 3.1, where EOS Utility software provides remote control of key camera settings, triggering and image transfer. Clicking the timer/stopwatch icon in EOS Utility's remote shooting window activates interval timer shooting, allowing multiple shot sequences to be acquired, which can then be aligned and stacked later in a single image.
The Canon EOS Ra's always-on low-energy Bluetooth and Wi-Fi connectivity also enable images and video to be captured remotely via the Canon Camera Connect app installed on a mobile device, as well as registering GPS data. And, of course, you can use the app's remote shutter release function for super-steady shooting.