The overwhelming majority of DSLR astrophotographers use Canon cameras and, to a lesser extent, Nikon cameras. This is not to say that other manufacturers don't make some DSLR cameras that might be useable for long-exposure deep-sky astrophotography, it's just that examples are hard to find, so it's difficult to know which cameras to recommend. Therefore, we will stick to Canon and Nikon cameras in this overview.

DSLR Development

Early first generation DSLR cameras made before 2003 had high levels of noise. These cameras did not perform very well for long-exposure deep-sky astrophotography.

Second generation cameras made after 2003 were real breakthroughs in terms of noise. This is when astrophotography with DSLR cameras really started to become popular.

Later cameras were more evolutionary than revolutionary. Pixels got smaller so more could be crammed onto the same size chips, but new technologies, such as microlenses, kept the signal-to-noise ratios good. The later models of Canon cameras also did not suffer from amp glow, a red glow on the edges of the screen from the camera's electronics in long exposures. The latest models of Nikons have also improved amp glow.

The most recent generation of cameras have added more pixels, lower noise, live-view focus, dust reduction technology, higher bit depths and high-definition video.

For a long while, Canon was pretty far ahead of Nikon in terms of digital camera noise and high ISO performance. Camera noise is one of the most critical considerations in terms of quality for long-exposures for deep-sky astrophotography. By using the latest generations of Sony sensors, Nikon caught up to Canon, and for all practical purposes the two manufacturers are extremely close today in terms of the noise present in their latest DSLR camera offerings.

Today's Cameras

For casual astrophotography with stock cameras, as well as normal daytime photography, both Canon and Nikon offer some excellent cameras that are also very reasonably priced.

Canon today offers cameras that are a bit easier to use for astrophotography and better supported by specialized astrophotography software.

If you already have a Nikon system and Nikon lenses, then you will probably want to go with a Nikon DSLR for astrophotography. If you don't have a lot of money already invested in Nikon, then I would recommend going with Canon.

Canon's entry-level DSLRs have multiple names, depending on where they are sold. For example, the Canon T3i is sold in the United States, but in most of the rest of the world it is called the 600D. In Japan, it is called the Kiss X5.

Canon's professional series uses single digit nomenclature, e.g. "1D", "1D Mark IV", "1Dx", etc.
Canon's prosumer series uses double digit nomenclature, e.g. "70D".
Canon's entry-level series uses triple digit nomenclature, e.g. "700D".
Canon's beginner-level series uses quadruple digit nomenclature, e.g. "1100D"

In many cases, different models share the same sensor, such as the 600D, 550D, 7D, 60D, and 60Da.

Nikon's professional series uses single digit nomenclature, e.g. "D4".
Nikon's prosumer series uses triple digit nomenclature, e.g. "D800".
Nikon's entry-level and beginner level series lines have blurred, most are designated by quadruple digit nomenclature, e.g. "D3200".

Camera Comparison Chart

My web page Nikon and Canon DSLR Cameras Compared lists the following up-to-date camera specifications:

• Camera Model
• Price
• Pixel Pitch
• Pixel Array
• Sensor Size in millimeters
• Number of pixels
• Bit Depth
• Crop Factor
• Sensor Type
• Processor
• Memory Card Type
• Dust Reduction
• Live View availability
• Video Modes
• Audio recording for video
• Tilt LCD screen
• Computer Connection
• Announced
• Availability
• Price

Considerations for Long-Exposure Deep-Sky Astrophotography

Listed below are some things to consider when choosing between a Nikon and Canon DSLR camera for long-exposure deep-sky astrophotography. The list is not meant to be exhaustive as things change very rapidly in the world of DSLRs.

Canon

1. Canon recognizes that astrophotography is a specific use of their cameras and has produced the Canon EOS 20Da and 60Da, cameras that were specifically designed for astrophotography.

2. Canon offers EOS Utility which will remotely control the camera via a computer and USB cable. This comes with the camera for free. Nikon's software for remote control costs quite a bit extra.

3. More support for Canon cameras is available from third party software vendors, such as Images Plus and Nebulosity, Backyard EOS, EOS Camera Movie Record and Astro Photography Tool. Although some vendors are beginning to implement support for Nikon DSLRs, Canons overwhelmingly have the most support because so many more people are using Canons for astrophotography.

4. Canon EOS Digital SLR cameras normally use EF and EF-S auto-focus lenses. They can not easily use older Canon FD-mount lenses. Canon EOS DSLRs can, however, use many other camera manufacturer's lenses in manual mode with a simple mechanical adapter.

   When Canon designed their EOS system, they completely redesigned the lens mount. Canon's previous FD lens system for film SLR manual focus cameras are not made for EOS bodies. The lens flange to focal plane distance for the FD series is 42mm. The lens flange to focal plane distance on the EOS series is 44mm. The lens flange was re-designed, and old FD lenses will not mount on newer EOS bodies.

   You can get a simple mechanical adapter that will mount FD lenses on EOS bodies, but they will not focus at infinity because of the lens flange to focal plane distance difference. You can also get a more complex optical adapter that has lens elements that will allow focusing of FD lenses at infinity on EOS bodies, but the Canon version is no longer manufactured and is difficult to find and very expensive when available. The Canon optical adapter also had a 1.26x multiplier factor which made the focal length of the lenses longer and also slower by that factor. As with the use of any multiplier or converter, optical quality also suffered somewhat. Third party manufacturers also make optical converters, but their optical quality is very poor for astronomical images.

5. Because of the shorter lens flange to focal plane distance on Canon EOS bodies, other manufacturer's lenses (even Nikons) can be used on Canon DSLR bodies with inexpensive adapters, such as those by Fotodiox. Note that the lenses must be used in stop-down metering mode and auto-focus doesn't work, but these are not a necessity for astrophotography anyway. Many other brands of lenses can be used with adapters on Canon DSLR cameras.

6. Canon has a plug on the side of the camera body for a hard-wired remote shutter release. This allows you to completely automate the image acquisition portion of an astrophotography session with a remote release timer like the Canon TC-80N3. This device allows shooting numerous frames at a particular exposure with a pre-determined amount of time between exposures.

   Professional Canon camera models use a proprietary "N3" type plug. Mid-level and introductory level Canon camera models use a "E3" type plug that is a simple mini-stereo plug.

   Inexpensive remote release timers similar to the TC-80N3 are available with both types of plug. Go to Ebay and search for "Aputure Timer Remote" or "Remote Timer Control".

7. The latest generation of Canon cameras can be controlled with a computer through a single USB cable. Even long bulb exposures (exposures longer than 30 seconds) can be controlled with this single cable. Focusing with Canon auto-focus lenses, and Live View, can be seen and controlled over the USB cable with a computer.

Nikon

1. Because of the relatively long flange-to-focal-plane distance on the Nikon cameras, few lenses from other manufacturers can be used because they will not reach infinity focus with an adapter.

2. Most of the latest Nikon Digital cameras do have a hard-wired release plug. Although Nikon uses several different proprietary plug types, including the 10-pin MC-36, MC-DC2 and MC-DC1.

   Several older Nikon cameras, such as the D3000, D60, D40x, D40, D50 and D70 did not have a hard-wired plug at all for a remote release. These cameras could only use in infra-red remote release. This can be quite inconvenient. The Nikon infra-red, while inexpensive at $17, only has one button that triggers the shutter on the camera once, and must be used from in front of the camera where the IR sensor is located. It is difficult to automate an imaging session with just this remote release.

   The Nikon MC-36 Multi-Function Remote with the proprietary Nikon plug is made for the high-end Nikon cameras such as the D3X, D3S, D300S, D300, D3, D100, D200 D1 and D2 series. The MC-36 will allow automating an imaging session without the use of a computer.

   There are also much less expensive Chinese clones of the Nikon MC-36 that are available. Go to Ebay and search for "Aputure Timer Remote" or "Remote Timer Control".

3. If you already have a significant investment in Nikon Lenses you can save money by going with a Nikon DSLR and not having to replace all of your lenses. Many photographers have been loyal Nikon users for years. For these photographers, sticking with Nikon may save them a lot of money if they would have to replace an extensive collection of lenses. Many older Nikon F series lens will work on the latest DSLR bodies (with a couple of exceptions). Unlike Canon, Nikon did not change their lens mount when they went to autofocus lenses. Not all functions, such as autofocus will work on all of the Nikon DSLR bodies however.

4. Some Nikon entry-level cameras, such as the D3000, D60, D40 and D40x, will only autofocus with AF-S and AF-I Nikkor lenses. These cameras do not have an autofocus motor built into the camera body. They require an autofocus motor in the lens. Other lenses can be used on these bodies, but you will have to focus manually. This is not really a problem if you are shooting through a telescope however.

5. Early Nikon DSLRs must use an inconvenient "mode 3" work around to acquire true raw files from the Nikon DSLR cameras, documented on Christian Buil's web page. This appears to be true even for Nikon's D3 camera as documented here.

   Nikon apparently applies a mathematical median blurring filter to their images in these older cameras after the in-camera dark frame subtraction for built in noise-reduction. This occurs even before the raw image is written to the file. To work around this and get a true raw file, it is necessary to physically turn the camera off during the in-camera dark frame acquisition. This is called the "mode-3" work around. This work-around made it difficult to automate the acquisition of multiple light frames which is the usual method of imaging with a DSLR for a dim astrophoto subject.

   The latest Nikon models however do not allow a mode 3 work around. Less of a blurring filter is applied to the latest low-noise Nikon cameras, so this is not really a problem anymore.

6. Nikon is also apparently truncating low-level signal during the digital-to-analog conversion performed by the electronics. See Christian Buil's Nikon D3 analysis. Emil Martinec reports that Nikon is doing the same thing to the D300. This may not be that serious concern since most of this low level signal may be noise.

   However, truncating low-level signal, and non-linearity make it hard to correctly calibrate deep-sky images taken with Nikon DSLR cameras and currently there isn't any software that will do this correctly.

7. Some early Nikon raw NEF files were not truly lossless, but this is probably not a serious problem since the compression scheme seems to be very efficiently applied, but might pose questions about correct calibration for advanced astrophotographic imaging.

   Newer Nikon DSLR camera models offer user selectable options for lossy compressed, lossless compressed, and uncompressed raw NEF files.

8. Nikon's latest generation of cameras can be controlled with a single USB2 cable and finally will allow bulb exposures (exposures longer than 30 seconds), but check with Nikon for specific models that support this feature before you buy one if this is important to you.