CHAPTER 13: Digital Astrophotography — What’s NEW?Chapter_13__Digital_Astrophotography.htmlChapter_13__Digital_Astrophotography.htmlshapeimage_2_link_0
Top DSLR Choices (as of September 2015)

Here are our current choices for recommended DSLR cameras, updating advice in Chapter 13.

Rapid changes in the DSLR market mean any advice in print is soon out of date. The cameras we recommend in our book (the Canon 40D and 50D among them) have long been discontinued. With the advances in sensors and in-camera processing technology they would not be good choices even as used cameras now, despite whatever bargain prices they might go for. Ditto on any other camera older than 4 or 5 years. 

Both Canon and Nikon, the two industry leaders, continue to advance the state of the art. Here’s a rundown on our currently recommended models, as of September 2015. Click on the headings to go to reviews or previews at .
Prices are approximate list prices in U.S. dollars. Older models often sell for less. All photos are from the manufacturer.


The Best from Canon - the 6D

Though now showing its age (the 6D was introduced in late 2012), in our opinion as of late 2015 the full-frame 6D remains Canon’s best camera for all forms of astronomy because of its low noise, still as low as any Canon DSLR as of this writing.

The Canon 6D offers 20.2 megapixels, modest by today’s standards. But in astronomy that’s good. It means the individual pixels remain large – 6.55 microns in the case of the 6D. This allows the 6D to provide lower noise than higher-megapixel cameras that pack in smaller 4- to 5-micron pixels.

The 6D is a full-frame camera – the sensor is 24 x 36mm, the same size as a 35mm film frame. The price is about $1,500, about as low as you’ll pay for a full-frame DSLR, making it a “best buy.” 

Have it modified with a filter that transmits more of the red H-alpha spectral line and you have a superb deep-sky camera. One of us (Terry) uses a filter-modified 6D from Hutech Scientific and loves it. Alan uses his stock 6D extensively for nightscape and time-lapse imaging.

Just keep in mind that being about three years old (a senior citizen in DSLR-years!) means the 6D must be in line for replacement soon by a rumored 6D Mark II. Another caveat: the 6D does not have the wonderful swing-out viewscreen of the cropped-frame Canon 70D and Rebel series cameras. Pity. 

But the 6D has two significant advantages over Canon’s cropped-frame cameras, some of which are no cheaper than the 6D:

Low noise. In our tests we found that the 6D offers about 2 stops better noise than its contemporary but now discontinued Canon 60Da, a camera made for astronomy.Noise is about one stop better than the standard-setting full-frame 5D MkII from 2008 that it replaced. The 6D can provide presentable images at previously unthinkable ISOs of 6400 or higher.

Dark Frame Buffer. Like all Canon full-frame cameras, the 6D offers a wonderful and little-known feature – a special buffer memory that allows it to take up to 4 long exposures, then internally apply a single dark frame taken automatically at the end of a sequence of exposures. This means, for example, that four 8-minute exposures and the single 8-minute dark frame for those exposures takes just 5 x 8 = 40 minutes to acquire. With Canon’s cropped-frame cameras, and all Nikons, having the camera take and subtract a dark frame internally means taking a dark frame after every light frame. A set of four 8-minute exposures with, say, the 70D or 760D will take 8 x 8 = 64 minutes to complete, vs. 40 minutes for the 5D MkII. That’s a real time-saver. Note that to maximize the number of frames the 6D can take you must set the camera to RAW + JPG. If set to take just RAW format images the 6D will shoot only 3 frames before the dark frame kicks in.

Canon also offers the 22-megapixel 5D MkIII, also introduced in 2012, with similar noise characteristics as the 6D and also offering a 4-frame image buffer when taking dark frames. However, the 5D MkIII’s added features, while of benefit to other photography, offer little of value to astrophotographers to justify its higher price. Will that also be true of the expected Canon 5D MkIV? We’ll see.

Canon’s 5Ds and 5DsR (at left), introduced in 2015, both break new ground in providing an immense 51 megapixels! 

To do this, their full-frame sensors employ 4.1-micron pixels, slightly larger than the 3.8-micron pixels in Canon’s latest 24-megapixel cropped-frame cameras. Tests at (linked above) show that while the 5Ds and 5DsR do offer stunning resolution, noise is higher than in the 6D and 5D MkIII, and is comparable to the cropped-frame 7D MkII with similar-sized pixels. Now, that’s still very good, but it is the price you pay for that level of resolution over such a large sensor. And their $3,600 to $4,000 price tags make them attractive to only the most dedicated. We can’t see us upgrading to a 5Ds anytime soon.

In picking a camera, keep in mind that what we say in our book about any full-frame DSLR will be true of the 20- and 22-megapixel 5D and 6D series cameras, and even more so for the 51-megapixel 5Ds — they will tax the quality of any optics attached to them, ruthlessly revealing both on-axis and off-axis aberrations. For deep-sky shooting through a telescope, you’ll need optics with field flatteners (built-in or added-on) designed to fully illuminate large-chip cameras. For piggyback shooting, you’ll need top-class glass — like the Canon L-series or Sigma Art Series lenses.

Great Value — The Canon EOS 70D

Now we enter the realm of “cropped-frame” cameras, with sensors 23 x 15mm in size. As a rule, the benefit is lower cost ... but at the price of increased noise, as manufacturers strive to pack more pixels into the smaller sensors. Sensors with 20 to 24 megapixels are the now the norm in cropped-frame cameras. 

Still, if the price of a full-frame Canon is a bit much, a Canon 70D, released in September 2013, is a good alternative at about $1,200. It is certainly more affordable than Canon’s top-end cropped-frame camera, the 20-megapixel 7D MarkII. 

At $1,800, the 7D MkII is in the same price league as the lower-cost full-frame cameras from Canon and Nikon, and yet produces higher noise because of its smaller 5.4-micron pixels. So why not go full-frame and get lower noise?

But if affordability is the concern, the 20-megapixel 70D offers similar — and very good — noise performance to the 7D MkII for much less money. As with the 5D MkIII, the extra features offered by the top-end 7D MkII (such as faster auto-focus and improved high-speed burst modes) are of little value to astrophotographers.

Indeed, the 7D MkII offers less, in that it lacks the wonderful articulated LCD screen (shown above) of the 70D and Rebels. It does so to ensure better weatherproofing. But unless you intend to use your camera on expeditions to extreme climates, this feature is of no value to us. Thus our advice to stay with the 70D for affordability, features, and decent noise performance about one stop below the full-frame models. (i.e. noise with the 70D at ISO 3200 is about what it is with the 6D at ISO 6400.)

Bargain Megapixels — The Rebel T6s/760D

If your budget can’t swing the 6D or 70D, consider the Canon Rebel series. 

Models change yearly but as of late 2015 the top end of the Rebel series includes the 750D, or T6i “Rebel” (as it is called in North America), and the 760D, or T6s Rebel. The 750D is about $750 while the 760D sells for about $850 (body only).

Image specs for both cameras are the same, but for the extra $100 the T6s offers more features such as a top LCD panel. While very handy in some situations, this screen is of now of less value with both cameras offering an articulated rear touch screen. 

The main upgrade that these Rebels provide over earlier Rebels is a 24-megapixel sensor, vs. 18 megapixels for the previous T5i. In theory this should make noise worse, but improvements to the on-board DIGIC processing in part counteract the increase in noise due to the smaller pixels. So noise performance is still very good, though not as good as in the 70D and 7D MkII, and noticeably worse than in the 6D.

But for those looking for a great starter DSLR for astrophotography, the Rebels continue to offer excellent value. Just keep in mind that as far as the all-important noise spec goes, the ranking from best to worse is: 6D > 5Ds, 70D & 7D MkII > 750D/760D.

A Used Canon 60Da? 
Introduced in 2012, the 18-megapixel Canon 60Da offered a sensor filter designed to transmit more of the deep red end of the spectrum, particularly the H-alpha wavelength, so that red nebulas will record with more detail and deeper red tones. We’re big fans of filter-modified cameras but these usually require having the camera modified by a third party. In this case, Canon did the mod for you as a factory-installed feature. 

The 60Da worked very well, but did not provide as great a sensitivity to red H-alpha emission nebulas as the after-market modified cameras offer. 

On the other hand, daylight images taken with the 60Da looked nearly normal, with little need for special filtration or post-processing color correction. A 640 x 480 Movie Crop mode also makes this a fine camera for lunar and planetary video imaging. And the articulated screen is endlessly convenient. One of us (Alan) still uses his 60Da often, though usually for bright subjects, not faint deep-sky targets.

A used 60Da might be an excellent bargain at the right price, but its noise levels, while good, are higher than in current models such as the 70D that have newer DIGIC processing. The 60Da could be used up to about ISO 1600. At higher ISOs noise was intrusive, requiring shooting and stacking of lots (16 or more) of exposures.


In the early years of DSLRs Canon took the lead for noise and low-light performance. However, Nikon has made great inroads at producing excellent cameras for low-light situations where high ISO speeds are required. As best we can tell, gone are the artifacts that plagued early Nikons, such as their reputation for “eating stars,” where the internal noise reduction Nikon applied to Raw files also wiped out star images. One of us (Alan) uses a stock Nikon D750 and loves it. But ...

The Best from Nikon — the D810a

Introduced in mid-2015, the D810a is Nikon’s answer to Canon’s “a” models designed for astronomy. But unlike Canon’s “a” cameras (the vintage 2005-era 20Da and the 60Da), the D810a is a full-frame camera, and at Nikon’s top end. It’s an astronomical version of their D810, but with a sensor filter designed to pass the deep red H-alpha wavelengths emitted by nebulas. 

The D810a also has slightly better noise performance than the D810, and has a much wider range of built-in exposure times, up to 15 minutes, without needing an external intervalometer. 

In addition, it offers a much brighter Live View screen aiding in focusing and framing dim subjects such as starfields, where normal cameras might show just one or two bright stars dimly at best. 

This is a 36-megapixel camera, with 4.9-micron pixels. Though getting on the small side, noise performance has been improved greatly and is only slightly worse, by less than a stop, than the best on this list, the Canon 6D and Nikon D750. See the DPReview page on the standard D810 to compare models. 

The Nikon D810a hits almost all the right specs, but its price tag of $3,800 makes it a choice only for serious shooters of the sky. But if you want the best for deep-sky astrophotography — and until and unless Canon comes out with a new “a” model — the Nikon D810a is arguably the best DSLR for astrophotography. Results we’ve seen are spectacular, and friends who own one rave about it. The benefit of the added resolution is noticeable in critical applications and huge enlargements.. 

Beside cost, its one drawback over the full-frame Canons is its lack of a “dark frame buffer” for taking a single dark frame and applying it to several images internally, to speed up acquisition of “calibrated” images. And it lacks the articulated LCD screen of the D750 so convenient for use on a telescope. In some respects, a D750a would have been the better offering.

The Nikon D750 — Better Still?

In some respects the Nikon D750 is better, in that with a 24-megapixel sensor, its 6-micron pixels produce lower noise than the D810 cameras. In side-by-side tests with the Canon 6D, which you can view at author Dyer’s website, the two cameras presented comparable noise performance, with the Canon no better, despite its slightly larger pixels. 

The D750 is a superb camera for nightscape shooting, exhibiting lower noise and image artifacts in the shadows than the Canon 6D due to the “ISO invariant” design of the Sony sensors used by Nikon. The webpage above, and most recent DSLR reviews on, such as of the D750 linked above, provide more details on this point of performance. It’s an important difference for nightscape imaging where Canon DSLRs often exhibit increased noise and purple discoloration in underexposed shadows. 

However, being a filter-modified camera, the D810a will do far better at recording red nebulas than the D750. But for most other forms of astrophotography, the $2,000 D750 is as good, if not better, than the much more costly D810a. And, rare among full-frame cameras, it has a tilt-up LCD screen. Hurray! 

For less money, the $1,500 Nikon D610 offers similar image quality to the D750, though without the added features of the D750, such as its higher-resolution tilting LCD screen, built-in WiFi, and higher ISO range. In our opinion, these alone make the extra cost of the D750 worth the investment for astrophotography.

The Retro-Styled Nikon Df

Introduced in 2013, the Df is a full-frame camera with styling reminiscent of the original Nikon F film cameras. Bucking the trend to more megapixels, the Df offers just 16 megapixels yielding 7.3 micron pixels. Only the Sony a7s (see below) uses a full-frame sensor with larger pixels. 

This does, indeed, produce excellent noise performance, thus its inclusion in our survey. 

However, advances in the internal processing on more recent Nikons means that models such as the D750 now offer similar low noise, despite the higher megapixel count, and yet at a comparable price. 

The Df also lacks any video recording ability. Unless you are an old Nikon film camera fan drawn to the Df’s  nostalgic styling, the Df likely isn’t a good value now. 

Lower Priced Nikon — the Cropped-Frame D7200

As with Canon, Nikon has a host of lower-priced entry-level models. The D7200, for $1,200 (body only), offers 24 megapixels, the same as the D750. But ... this is a cropped-frame camera, the best in Nikon’s line, and competitive with the Canon 70D and 750D/760D for image specs. Nikon calls their cropped-frame models “DX”, vs. their “FX” full-frame cameras. 

Like other 24-megapixel cropped-frame cameras now popular, the D7200 uses 3.9-micron pixels. That certainly means higher noise than with full-frame cameras with 6-micron pixels, in this case by about a stop (i.e. images with the D7200 at ISO 3200 will have noise similar to the Nikon D750 at ISO 6400). 

Now, that’s certainly not bad, and is about the best that current Nikon DX cameras can do, bettering their lower-priced D5500 and D3300, and even bettering the older Canon 70D. So if your budget is around $1000, and Nikon is your preferred brand, the D7200 is the best choice. Just keep ISOs lower and apply judicious noise reduction in processing to mitigate the added noise, good advice for using any cropped-frame camera.

To summarize, with Nikon, the noise ranking from best to worse is: D750, D610 & Df > D810a > D810 > D7200.


Pentax K-3II

Avid fans of Pentax — and you’d have to have been a loyal fan since the film days to have stayed with them — have an interesting camera to pick from in the new K-3, the Mark II model. 

This is a cropped-frame camera with 24 megapixels, to compete with the Nikon D7200 and Canon D750/760 models. Price, at about $1,100, is comparable to the D7200, and to the Canon 70D. However, at high ISOs, noise levels are slightly worse than with the 70D, and certainly worse than the D7200. Noise is on par with the Canon D750/D760 models. OK but not the best.

But here’s the trick: with the K-3II noise can be improved upon by using its unique “Pixel Shift” option, which takes four images in rapid succession, shifting the sensor by a pixel each time, then stacks them internally to smooth noise. Astrophotographers routinely do this in processing but the Pentax K-3II can do it automatically in-camera. The result is an improvement in noise by a factor of about two, bringing the K-3II to a similar, if not better, level of noise performance as the D7200. That’s certainly excellent for a 24-megapixel cropped-frame camera. This feature will be of use only for scenes where nothing is moving, but it would reduce noise in static nightscapes.

To follow the moving sky, the ability of the K-3II to move its sensor around has been exploited by Pentax designers to add what’s called the “Astrotracer” feature. The camera uses its GPS knowledge of where it is on Earth, and of its pointing direction and tilt angle from its internal compass and tilt meter, to shift its sensor slowly during long exposures to track the stars, in exposures up to about 5 minutes. There’s no need for a motorized tracking device. Some older Pentaxes can also be adapted to add Astrotracer capability by adding an optional GPS unit. See the Pentax Astrotracer webpage linked to above for details.

That said, we’ve not used the Pentax to know how well its Astrotracer and Pixel Shift functions work. Pentax fans, let us know!


Sony a7s

In early 2014 Sony created a minor stir in the photo world with the introduction of the a7s camera to their series of Alpha cameras. As with DSLRs, these cameras all have interchangeable lenses, but they have no reflex mirrors nor optical viewfinders. All viewing is done through the electronic viewfinder. They are what are collectively labeled as “mirrorless” cameras, or DSLMs. 

The a7s model is designed to provide low noise even at ultra-high ISO speeds, particularly for use when shooting video in low-light situations. As such it uses a full-frame sensor with only 12 megapixels, resulting in large 8.5-micron pixels, a size we haven’t seen since the early days of full-frame DSLRs, such as the original 13-megapixel Canon 5D a decade ago.

Noise is impressively low, making the Sony a7s a new favorite among nightscape photographers. But, you do sacrifice resolution. Do you really want to go back 10 years in resolution? 

And noise tests at DPReview show that, though impressive, the a7s noise levels improve upon the Nikon D750, a current full-frame leader, by no more than one stop, if that. Is that worth the loss in resolution? And for $2,400? This is a camera first and foremost for videographers (it can output a 4K video signal to an external recorder) wanting to shoot in available light.

The benefit of a mirrorless camera is that the camera body is much smaller, thinner, and lighter. However, switching to a mirrorless system like the Sony Alpha, means acquiring all new lenses, or purchasing an adapter to attach your existing DSLR lenses that are all made to focus on a sensor located about 55mm behind the lens flange. This inevitably means sacrificing the autofocus functions of your non-Sony lenses.

Attaching an Alpha camera to a telescope will require a special adapter and spacer tube to ensure it is mounted at the correct distance from any field flattener lens to the sensor focal plane. 

And you’ll need to control the camera – existing software programs may not recognize the Sony. There is no hardware remote or intervalometer connection. Instead, remote control is through a wireless WiFi connection to your mobile device running Sony’s Play Memories mobile app.

For an extensive review, the one that really introduced the a7s to astrophotographers, see Ian Norman’s review at his excellent website. 

We have not used the Sony, and considering its cost and complexity to adapt it to our telescopes, lenses, and time-lapse gear, we aren’t likely to. But Sony fans, let us know how you like it! 


— September 2015