I've used a few modified Canon DSLR cameras over the years for my astrophotography, including an Astro40D from Central DS which I used for many years of widefield astrophotography including one of my favourite ever images of the Southern Cross region.
With a new home (at least part-time) under dark skies I decided it was time for an upgrade and took the plunge with the CDS-5D (see disclosure below). This is my review of the camera, which will be updated with more tests and images.
CDS-5D with Pentax 300mm lens
Single 5 minute sub-exposure, f5.6, ISO800
My first target was the region around the Lagoon and Trifid Nebula, heading down in the west for the season but still high enough for a good test. When I reviewed this single 5 minute sub-exposure above on my computer the next day, I was a) very impressed with the image quality to the corners of the frame from the 300mm medium format lens and b) satisfied that I had a camera capable of impressive results that was going to keep me busy for many nights to come. It was the first time I had been excited about deep sky imaging for quite some time.
About the CDS-5D
The CDS-5D from Central DS in South Korea is a heavily modified Canon 5D Mark III DSLR.
The CDS-5D is no longer recognisable as a Canon camera and has very few DSLR-like functions available: no battery, no autofocus, no metering, no display screen and Bulb only exposures of 1 second or longer. It is both spectrum modified and with a hefty cooling system as well. This is a camera dedicated to serious astrophotography.
The filter that encloses the sensor and seals the camera is a Hoya MC clear filter meaning that the sensor has a wide spectral response. When used with refractors you will at least need a UV/IR cut filter in the optical train to prevent bloated stars caused by UV/IR light that the optics are not well corrected for.
What's in the Box?
The CDS-5D comes well packaged in a black camera case. The main additional item included is a temperature controller. It connects to a port on the camera and couldn't be any easier to use.
The default connector for the CDS-5D is a Canon EOS bayonet mount which has a 2" filter holder included. This can be quickly and easily swapped out without removing the lens which is handy, especially if you want to try Hydrogen-Alpha imaging. As per the Central DS diagram below, this maintains the standard EOS flange to sensor distance.
Instead of the bayonet mount there is also a low profile 2" nose-piece for use with a 2" focuser and a low profile wide T-thread adapter. The filter holder is excluded with either of these options so if using a refractor you will likely need a UV/IR blocking filter somewhere else in the image train. However, these low profile connectors may be attractive for achieving full illumination of the sensor with fast Newtonian reflectors.
For use with camera lenses, there is a hefty right angle bracket for directly mounting the camera on a tripod or equatorial mount. This is 15mm thick so you will never have any concerns about flex when using this. Most of the time the camera will probably be attached directly to the telescope or telephoto lens but there is a fair amount of weight (1.5kg) to this camera which your focuser has to be able to rigidly support.
The CDS-5D connects to your computer and is recognised like any other Canon 5D Mark III and can be easily controlled with EOS Utility (Bulb Exposures only) including Liveview. Central DS also include a license for Backyard EOS camera control software. I have some issues with the camera connection dropping out at the moment so have stuck with EOS Utility for the moment (I think the EOS software is interrupting the Backyard EOS connection).
The CDS-5D also includes a factory installed WiFi SD card (for storing and accessing images when used in stand-alone mode). This can't be accessed or changed like the memory card in a normal DSLR.
Central DS claim a cooling capability of 40 degrees below ambient. I have achieved approximately 35-37 degrees cooling in my early tests. No doubt a little more could be seen under ideal test conditions. This is a serious amount of cooling for a DSLR. My old 40D had only 18 degrees of cooling but even that was enough for a compelling reduction in thermal noise.
Central DS have also now implemented a small resistance heater to ensure that the clear sensor window remains free of condensation even at these high levels of cooling.
Ease of Use
I can (literally) use DSLRs in the dark. I've used so many they are second nature to me. But using the CDS-5D is more like operating a CCD camera. All of the buttons and controls have been removed so framing, focus and exposure setting must be done external to the camera. I quickly adapted to that process again though. Controlling the camera via EOS Utility or Backyard EOS is pretty straightforward, switching to Liveview for framing and focus etc. You can also use MaximDL to operate the camera, but so far I find the framing and focus at least to be easier in EOS Utility.
Here is the image at top shown straight out of the camera:
Single 5 minute sub-exposure, Unprocessed
For the version at the top of this post, I used Lightroom to quickly correct the White Balance, applied a few brightness/contrast adjustments and standard noise smoothing levels. A quick and easy and very impressive result. Click any image to see high-res versions on SmugMug.
The test below compares a single 5 minute sub-exposure using my off-the-shelf Canon 6D (very similar sensor to the 5D Mark III) with the CDS-5D. These were shot using a Takahashi FS-102 with an Astro-Tech field flattener. Focal length is 810mm at f/8.
Canon 6D, Takahashi FS-102, 5 minutes, ISO800
CDS-5D, Takahashi FS-102, 5 minutes, ISO800
The significantly reduced noise due to the high degree of cooling and the greater spectral response of the camera is fairly evident. Remember that these are single sub-exposures of a faint target at a slow focal ratio of f/8. Below is what 70 minutes of exposure looks like (still a very short exposure time by my standards). Although there are some optical issues, this sensor performance is impressive (click for large sizes).
CDS-5D, Takahashi FS-102, 70 minutes, ISO800
Stand Alone Operation
While most people will probably use the CDS-5D as part of a computer controlled system, the CDS-5D can be operated like a DSLR (even though it doesn't look like one). The connection for a remote timer/intervalometer is the same N3 connector as used on all Canon's full frame and higher end DSLRs. So you can simply plug in the 12V power supply and trigger exposures like normal. You connect to the camera via WiFi on your smartphone or computer to view and download images.
Why not a modified 6D?
Although I had seen the CDS-5D some time ago, I waited hoping that a modified 6D would be cheaper but provide the same performance (as you would be throwing away the extra features of the 5D Mark III anyway). In April 2014 Yun Lee at Central DS advised that they were studying development of an Astro6D but that the inner space of 6D restricted their options. They were going to develop a 'semi-cooled' version but could not say when it would be ready. At that point I decided to dive in with the available option.
Is this camera for you?
For most of my imaging career, DSLRs have had two key advantages over astronomical CCD cameras (which otherwise have had the clear theoretical performance advantage):
- DSLRs can be operated as a stand-alone camera without complicated computer control and additional power requirements. This simplicity has made much of my widefield astrophotography possible, as I've combined it with camping trips and quick weekends away where I did not have the time or power supply for more complex imaging. I've captured many many hours of data quickly and easily like this. It's like visual observing - better the simple and easy to use telescope you do use than the large and expensive super scope that stays in the cupboard because you can't be bothered transporting it or setting it up.
- DSLRs work great with camera lenses. It is often not possible to use mono CCDs with standard lenses as there is insufficient back-focus to accommodate the filters. Lenses (obviously) mount very easily onto DSLRs and their sensors are mounted with high precision usually avoiding 'sensor tilt' issues that affect CCD cameras when being used with fast lenses. And using auto-focus or LiveView it's quick and easy to focus.
- Because they are manufactured at large scale, DSLRs offer quality sensors at nice prices. The modification of course starts to reduce this differential.
Cooled DSLRs add significantly to the power requirements, but still maintain their overall simplicity. However, cameras as heavily modified and cooled as the CDS-5D are now more comparable to colour CCD cameras in terms of performance than they are to conventional DSLRs. The CDS-5D can still be operated in stand-alone mode, offering a simpler alternative, but most users will probably opt for full computer control.
At a price of around $4,700 this is a serious camera purchase decision. You can also get your own 5D Mark III modified for around $1,700. So is it the right camera for you?
While the CDS-5D can be used with narrow-band filters, if your interest lies in deep-sky narrow band imaging, either by choice or necessity through imaging from city locations, then a mono CCD camera is the logical choice. If you have decided on LRGB imaging with a mono sensor then this is unlikely to change your mind either (although the performance may be surprisingly close).
But if you want to shoot one-shot colour images with a large sensor, then the CDS-5D is a serious competitor. I'm not an expert in CCD sensors and camera models, but an Atik 11000 colour camera costs $5,600 and uses an older Kodak sensor which may not match the performance of this latest generation Canon CMOS sensor. I welcome feedback on that topic.
Where the CDS-5D stands out is for imaging with camera lenses. You need quality optics to work with large sensors, but if you have the right lenses, the CDS-5D offers some seriously attractive wide-field imaging opportunities that would be hard to match with other packages in either price or performance. And the ease with which the CDS-5D can be used with Canon EOS lenses gets you going quickly and makes for productive low-stress imaging. As I said at the start, that single sharp and smooth sub-exposure of the Lagoon/Trifid region has got me excited about the possibilities this camera offers for my imaging.
Full Disclosure: Central DS provided a discount for my purchase of this camera. I offered to do that as there were few published images and user reviews of the CDS-5D at the time.