Testing the Canon 6D Mark II for Deep-Sky


6D MkII on Cygnus

Following up on my earlier tests, I compare the new Canon 6D MkII camera to earlier Canon full-frame models in long, tracked exposures of the Milky Way.

A month ago I published tests of the new Canon 6D MkII camera for nightscape images, ones taken using a fixed tripod in which exposures usually have to be limited to no longer than 30 to 60 seconds, to prevent star trailing.

Despite these short exposures, we still like to extract details from the dark shadows of the scene, making nightscape images a severe test of any camera.

I refer you to my August 9, 2017 blog Testing the Canon 6D MkII for Nightscapes for the results. The 6D MkII did not fare well.

Here I test the 6D MkII for what, in many respects, is a less demanding task: shooting long exposures of deep-sky objects, the Milky Way in Cygnus in this case.

Why is this an easier task? The camera is now on a tracking mount (I used the new Sky-Watcher Star Adventurer Mini) which is polar aligned to follow the rotation of the sky. As such, exposures can now be many minutes long if needed. We can give the camera sensor as much signal as the darkness of the night sky allows. More signal equals less noise in the final images.

In addition, there are no contrasty, dark shadows where noise lurks. Indeed, the subjects of deep-sky images are often so low in contrast, as here, they require aggressive contrast boosting later in processing to make a dramatic image.

While that post-processing can bring out artifacts and camera flaws, as a rule I never see the great increase in noise, banding, and magenta casts I sometimes encounter when processing short-exposure nightscape scenes.


6D MkII at Four ISOs
The Canon 6D MkII at four typical ISO speeds in tracked exposures.

6D at Four ISOs
The original Canon 6D at four typical ISO speeds in tracked exposures.

5D MkII at Four ISOs
A Canon 5D MkII that has been filter-modified at four typical ISO speeds in tracked exposures.
For this test, I shot the same region of sky with the same 35mm lens L-Series lens at f/2.2, using three cameras:

• Canon 6D MkII (2017)

• Canon 6D (2012)

• Canon 5D MkII (2008)

Note that the 5D MkII has been “filter-modified” to make its sensor more sensitive to the deep red wavelengths emitted by hydrogen gas, the main component of the nebulas along the Milky Way. You’ll see how it picks up the red North America Nebula much better than do the two off-the-shelf “stock” cameras. (Canon had their own factory-modified “a” models in years past: the 20Da and 60Da. Canon: How about a 6D MkIIa?)

I shot at four ISO speeds typical of deep-sky images: 800, 1600, 3200, and 6400.

Exposures were 4 minutes, 2 minutes, 1 minute, and 30 seconds, respectively, to produce equally exposed frames with a histogram shifted well to the right, as it should be for a good signal-to-noise ratio.

Noisy deep-sky images with DSLR cameras are usually the result of the photographer underexposing needlessly, often in the mistaken belief that doing so will reduce noise when, in fact, it does just the opposite.

The above set of three images compares each of the three cameras at those four ISO speeds. In all cases I have applied very little processing to the images: only a lens correction, some sharpening, a slight contrast and clarity increase, and a slight color correction to neutralize the background sky.

However, I did not apply any luminance noise reduction. So all the images are noisier than what they would be in a final processed image.

Even so, all look very good. And with similar performance.

All frames were shot with Long Exposure Noise Reduction (LENR) on, for an automatic dark frame subtraction by the camera. I saw no artifacts from applying LENR vs. shots taken without it.

The 6D and 6D MkII perhaps show a little less noise than the old 5D MkII, as they should being newer cameras.

The 6D MkII also shows a little less pixelation on small stars, as it should being a 26 megapixel camera vs. 20 to 21 megapixels for the older cameras. However, you have to examine the images at pixel-peeping levels to see these differences. Nevertheless, having higher resolution without the penalty of higher noise is very welcome.


3 Canons at ISO 1600
The three cameras compared at ISO 1600. Note the histogram and region of the frame we are examining up close.

3 Canons at ISO 3200
The three cameras compared at ISO 3200. Note the histogram and region of the frame we are examining up close.

3 Canons at ISO 6400
The three cameras compared at ISO 6400. Note the histogram and region of the frame we are examining up close.
Above, I show images from the three cameras side by side at ISOs 1600, 3200, and 6400. It is tough to tell the difference in noise levels, the key characteristic for this type of astrophotography.

The new 6D MkII shows very similar levels of noise to the 6D, perhaps improving upon the older cameras a tad.

Because images are well-exposed (note the histogram at right), the 6D MkII is showing none of the flaws of its lower dynamic range reported elsewhere.

That’s the key. The 6D MkII needs a well-exposed image. Given that, it performs very well.


3 Canons Stacked & Processed
The three cameras in stacked and processed final images.
This version shows the same images but now with stacked frames and with a typical level of processing to make a more attractive and richer final image. Again, all look good, but with the modified camera showing richer nebulosity, as they do in deep-sky images.

The lead image at the very top is a final full-frame image with the Canon 6D MkII.


As such, based on my initial testing, I can recommend the Canon 6D MkII (and plan to use it myself) for deep-sky photography.

Indeed, I’ll likely have the camera filter-modified to replace my vintage yet faithful 5D MkII for most of my deep-sky shooting. The 6D MkII’s tilting LCD screen alone (a neck, back, and knee saver when attached to a telescope!) makes it a welcome upgrade from the earlier cameras.

The only drawback to the 6D MkII for deep-sky work is its limited dark frame buffer. As noted in my earlier review, it can shoot only three Raw files in rapid succession with Long Exposure Noise Reduction turned on. The 5D MkII can shoot five; the 6D can shoot four. (A 6D MkIIa should have this buffer increased to at least 4, if not 8 images.)

I make use of this undocumented feature all the time to ensure cleaner images in long deep-sky exposures, as it produces and subtracts dark frames with far greater accuracy than any taken later and applied in post-processing.


I hope you’ve found this report of interest.

With the 6D MkII so new, and between smoky skies and the interference of the Moon, I’ve had only one night under dark skies to perform these tests. But the results are promising.

For more tips on deep-sky imaging and processing see my pages on my website:

Ten Tips for Deep-Sky Images

Ten Steps to Deep-Sky Processing

Thanks and clear skies!

— Alan, September 7, 2017 / © 2017 Alan Dyer / amazingsky.com

 

A Plethora of Perseids


A composite depicting the Perseid meteor shower on the night of Wednesday, August 12, 2015 as shot from southern Alberta, Canada.  The image takes in a wide swath of the north and eastern sky, including the radiant of the shower in Perseus at left of centre, near the Double Cluster visible as a clump of stars. All the Perseids can be traced back to this point. Also in the image: the summer Milky Way and, at left, a dim aurora in green and magenta that was barely visible to the eye but was picked up by the camera. The Andromeda Galaxy is at centre. The Pleiades is just on the horizon. Apart from some haze from forest fire smoke, it was a near perfect night: warm, dry, just a little wind to keep the bugs at bay, and no Moon. A perfect night for a meteor watch.  This is a layered stack of 35 images recording three dozen meteors (most Perseids but also a couple of sporadics not aimed back to the radiant in Perseus, such as the bright one at far left).  The 35 images were selected from 200 shot from 11 pm to 2:30 am that night, with most frames not picking up any meteors. This composite is from the 35 taken over the 3.5 hours that did record a meteor. Each exposure is 1 minute at f/2.8 with the 15mm full-frame fish-eye, on the Canon 5D MkII at ISO 3200 (a couple of the early shots in the sequence were at ISO 1600 for 2 minutes).  The camera was tracking the sky on the Sky-Watcher Star Adventurer tracker, so all images of the stars are aligned and registered out of the camera, with the meteors in their proper position relative to the stars and radiant. I masked out a couple of satellite and aircraft trails that were distracting, and took away from the point of illustrating the radiant of the meteor shower.  The horizon, however, is from one image, taken early in the sequence. Some of the blue in the sky comes from one of the early shots taken in deep twilight but that contained a nice meteor. And I liked the blue it added.  All stacking and processing with Adobe Ca

It was a good year for Perseid meteors, as they shot across the sky in abundance on dark-of-the-Moon nights.

Last week, August 11 and 12 proved to be superb for weather in southern Alberta, with clear skies and warm temperatures perfect for a night of watching and shooting meteors.

On both nights I had identical camera rigs running, all from my rural backyard. These images are from the peak night, Wednesday, August 12.

The main image at top is with a 15mm ultra wide lens, on a camera that was tracking the sky as it turned. Like many meteor photos these days it is a layered stack of many images, in this case 35, to put as many meteors as possible onto one frame.

While the result does illustrate the effect of meteors streaking away from the radiant point, here in Perseus, it does lend a false impression of what the shower was like. It took me 3.5 hours of shooting to capture all of those meteors.

Note the aurora as well.

The Perseid meteor shower on peak night of Wednesday, August 12, 2015, showing meteors radiating from the “radiant point” in northern Perseus, then rising in the northeast sky. One bright sporadic, non-Perseid meteor is at left, and a small sporadic is near the horizon at right. The meteor at far left, top, may be a satellite streak.  The Andromeda Galaxy is at upper right. A dim aurora is at left in the northeast. The setting is a ripening canola field at home.  This is a stack of 16 images, one for the “base layer” ground and sky, containing a bright meteor, and 15 other images taken as part of the same sequence, each containing a meteor, layered with Photoshop using Lighten blend mode. I rotated each of the additional “meteor layers” around Polaris at upper left, so the sky aligned closely, putting the meteors in close to their correct position relative to the stars, to accurately illustrate the radiant effect. This was necessary as this sequence was shot with a fixed, non-tracking camera (the Canon 6D) using a 14mm Rokinon lens at f/2.8. Each exposure was 1 minute at ISO 3200. The 16 meteor frames came from a set of 212 frames taken over 3.5 hours. I layered in only the frames with meteors.  Frames were taken from 11 pm to 2:30 am MDT.

With this camera I used a wide 14mm lens, but with the camera on a fixed tripod. I again blended frames, 16 of them, to show the meteors radiating from Perseus.

Because the camera was not tracking the sky, later in Photoshop I rotated each frame relative to a lower “base-level” image, rotating them around Polaris at top as the sky does, in order to line up the stars and have the meteors appear in their correct position relative to the background stars and radiant point.

Note the errant bright “sporadic” meteor not part of the shower.

The Perseid meteors shooting through Cygnus and the Summer Triangle area of the summer Milky Way, on the night of Wednesday, August 12, 2015. Deneb is the star at top left, Vega at top right, and Altair at bottom. The Perseids shoot across the frame from top left to bottom right. Other streaks are sporadic meteors or short satellite trails. I masked out other long satellite trails that were distracting to the image’s focus on depicting Perseids. This is a stack of 24 images, each with a meteor or two, taken over a 3.5-hour period that night, with each exposure being 1 minute at f/2, with the 24mm Sigma lens and Nikon D750 at ISO 1600. The 24 image with meteors were selected from a total of 214 shot for this sequence, with most frames not recording any meteor, and perhaps only satellites or aircraft.

Camera number 3 was aimed straight up for 3.5 hours, toward Cygnus and the Summer Triangle, in hopes of nabbing that brilliant fireball streaking down the Milky Way. I got a nice “rain of meteors” effect but the bright bolide meteor eluded me.

This was certainly the best year for the Perseids in some time, with it coinciding with New Moon.

Later this year, the Geminids will also put on a good show at nearly New Moon, on the nights of December 13 and 14. So if you liked, or missed, the Perseids, take note of the dates in December.

However, for many of us, a Geminid watch is a very, cold and snowy affair!

— Alan, August 18, 2015 / © 2015 Alan Dyer / www.amazingsky.com 

Mt Kobau Milky Way


Summer Milky Way from Mt Kobau

The Milky Way towers over the pine trees and sagebrush of Mt. Kobau in the South Okanagan, BC.

It’s been a fine two nights renewing friendships and seeing stars at the summit of Mount Kobau near Osoyoos. I’ve not been here for a dozen years but the timing worked out this year for me to visit the annual Mt. Kobau Star Party, the first star party I attended back in the 1980s.

It’s a rough road to the summit but the reward is a beautiful landscape and skyscape.

The main image above is from Monday night and takes in the Milky Way from horizon to zenith, from Sagittarius to Cygnus. I used a 15mm lens and Canon 5D MkII riding on a new Sky-Watcher Star Adventurer tracking unit, which worked beautifully.

Mt Kobau Milky Way Panorama #1

This image, similar to one I took a few nights ago at the Table Mountain Star Party, is a 360° panorama of the land and sky at the Kobau summit. It is a stitch of 8 segments, each 45-second exposures at ISO 6400 with the Canon 6D and 14mm Rokinon lens.

Unfortunately, it shows the light pollution glows from Osoyoos and Oliver that have grown over the last 3 decades and now impinge upon the Kobau skies.

Cygnus and Lyra (2014)

This image is a tracked closeup of the Cygnus and Lyra area of the Milky Way, taken with a 50mm lens and the 5D Mark II riding on the Star Adventurer for a stack of five 10-minute exposures. It is rich in the red nebulosity of the Cygnus spiral arm and takes in the field that the Kepler satellite stared at for 4 years looking for alien planets.

I’m heading home but the star party continues all week, building to the weekend when most people will be attending, under prospects of clear skies and warm weather.

– Alan, July 30, 2014 / © 2014 Alan Dyer

 

The Veil Nebula in Cygnus


NGC 6960 & 6992-5 Veil Nebula (92mm 5DII)

This is what’s left of a star that exploded thousands of years ago.

I shoot this object every year or two, so this is my 2013 take on the Veil Nebula. For last year’s see Star Death Site, a post from September 2012.

The Veil Nebula is a supernova remnant. The lacework arcs are what’s left of a massive star that blew itself to bits in historic times. This object, one of the showpieces of the summer sky for telescope users, is now high overhead at nightfall, off the east wing of Cygnus the swan.

I shot this a couple of nights ago using a 92mm-aperture refractor that provides a wide field of view to easily frame the 3-degree-wide extent of the nebula. The image is a stack of five 15-minute exposures with a filter-modified (i.e. red sensitive) Canon 5D MkII camera at ISO 800. Stacking the images helps reduce noise.

The colours in this object make it particularly photogenic, with a contrast of magenta and cyan. At right, a sharp-edged area of obscuring interstellar dust tints the sky brown and dims the stars.

– Alan, October 9, 2013 / © 2013 Alan Dyer

The Cocoon Nebula in Cygnus


Cocoon Nebula IC 5146 (92mm 5DII)

A cocoon of glowing gas sits at the tip of a dark cloud of interstellar dust.

It’s been months since I’ve shot more “traditional” astrophotos, meaning images of deep-sky objects through telescopes. But the last couple of nights have been excellent, and well-timed to the dark of the Moon.

This is the Cocoon Nebula in Cygnus, aka IC 5146. It is a cloud of gas about 4,000 light years away where new stars are forming. They are lighting up the gas to glow with incandescent pink colours.

The Cocoon sits at the end of snake-like dark nebula known as Barnard 168 which, in the eyepiece of a telescope, is usually more obvious than the subtle bright nebula. Photos like mine here, with long exposures and boosted contrast and colours, make nebulas look much brighter and more colourful than they can ever appear to the eye.

For the technically curious, I shot this with a 92mm diameter apochromatic refractor, the TMB 92, and a Borg 0.85x flattener/reducer, a combination that gives a fast f-ratio of f/4.8 with a very flat wide field. I also used my now-vintage filter-modified Canon 5D MkII at ISO 800. This is a stack of five 12-minute exposures, registered and median-combined in Photoshop to smooth out noise. All processing was with Adobe Camera Raw and Photoshop CC. The telescope was on an Astro-Physics Mach 1 mount, flawlessly autoguided with an SBIG SG-4 autoguider.

– Alan, October 6, 2013 / © 2013 Alan Dyer

 

Star-Making Clouds in Cygnus


Cygnus Nebulosity (135mm 5DII)

The centre of Cygnus is laced with an intricate complex of glowing gas clouds.

This is another shot from earlier this week, under ideal skies, in a view looking straight up into Cygnus the Swan. This is a telephoto lens shot of the amazing array of nebulas in central Cygnus, around the bright star Deneb.

At left is the North America and Pelican Nebulas. At right is the Gamma Cygni complex and the little Crescent Nebula at lower right.

Here we’re looking down our local Cygnus-Orion arm of the Milky Way into a region of star formation rich in glowing hydrogen gas and dark interstellar dust. These clouds lie about 1500 to 3000 light years away. Dotting the field are hot blue stars newly formed from the raw ingredients making stars in Cygnus.

At top, the clouds have a lacework appearance, like sections of bubbles. Perhaps these are being blown across space by the high-velocity winds streaming from the young stars.

– Alan, September 13, 2013 / © 2013 Alan Dyer

 

The Summer Triangle Stars


Summer Triangle in the Milky Way

The trio of Summer Triangle stars flank the Milky Way in the dying days of summer.

I shot the featured image above two nights ago on a perfect late summer night from home. Skies were dark and transparent, with no aurora and little airglow to taint the sky.

The image takes in the Summer Triangle stars of Vega (top), Deneb (left) and Altair (bottom). Vega and Altair straddle the summer Milky Way, but Deneb lies right in the thick of it, way down the Local Arm that we live in. Vega and Altair are nearby normal stars, only 25 and 16 light years away. But Deneb is a blue supergiant, shining from 1400 light years away, and one of the most luminous stars in the catalog.

The Milky Way through this area of sky is riven by twisting lanes of interstellar dust. A particularly dark patch sits above Deneb at top left. Then below Deneb the Milky Way gets split by the Great Rift that continues down into Aquila and Ophiuchus at lower right.

All along this part of the Milky Way, particularly around Deneb, the camera picks up a string of glowing red nebulas where stars are forming. The red comes from hydrogen atoms emitting deep red light, as hydrogen is wont to do.

Summer Milky Way from Backyard (Sept 9, 2013)

This image is from a couple of nights earlier. I used a wider angle lens to take in the full sweep of the summer Milky Way, from Sagittarius skimming the horizon, to Cassiopeia past the zenith at the top. You can see the Summer Triangle in the top half of the image, the part of the sky now overhead on early September nights from the northern hemisphere.

I took both shots with a filter-modified Canon 5D MkII placed on a little iOptron SkyTracker for tracked long exposures (4 to 5 minutes). The main image was with a 24mm Canon lens, the bottom image with a 14mm Rokinon lens.

– Alan, September 12, 2013 / © 2013 Alan Dyer