The Insight Astronomy Photographer of the Year Exhibition

It’s rare that you see much about astrophotography in the popular press or in museums, but this weekend I had the chance to see the exhibit for The Insight Astronomy Photographer of the Year contest. This contest is in its fifth year, drawing entries from around the world. The winners are not only published in a beautiful yearbook, but they are also exhibited at the Royal Observatory in Greenwich, UK. The exhibit is part of the free area, though if you are into astronomy, you may want to pay the fee to see the nearby observatory museum, where luminaries like Airy and Flamsteed worked. (Of course, you also get to stand on the prime meridian line, which is pretty cool too.)

As you can see the exhibit was popular with the public, which is heartening to see.

The winning images were printed and displayed on lightboxes, which really made them look fantastic. They also had a few video clips with interviews of the photographers playing. A few close-ups are below.

Overall, there seemed to be a bias toward nightscape images over deep-sky images, which makes sense, as it gives people a sense of their place in the universe, but I would personally like to have seen more. Two deep-sky images (not shown above), by Pavel Pech and Rolf Wahl Olsen,  were particularly impressive.

Each image listed the technical details and explained what you were looking at. Like the book, the exhibit quality was very high, and I know I came away inspired to get out with my camera more.

Lecture: Understanding Signal, Noise, and Resolution

Last night, I was honored to present a lecture to the New Jersey Astronomical Association’s imaging meeting. It’s a great group of people, and I’m sorry that I’m only connecting with them now.  Special thanks to Mike Franzyshen and Jim Roselli for the invitation.

In about an hour, I cover broad range of related topics:

• The statistics of shot noise, including the connections between Simeon-Denis Poisson and the particle theory of light
• Signal-to-noise ratio, with examples
• The effects of skyglow, with examples
• Resolution and sampling
• Aperture, focal length, and focal ratio

It was a lot of fun to put this lecture together, and during the research for it, I uncovered how Poisson’s life led to multiple insights about photons, none of which he was able to appreciate during his lifetime.

NOTE: At 40:30, I second-guessed myself, but the math on the slide is correct as written. The additional read noise is indeed 32. Since read noise is 10 per exposure, per the previous slide the additional noise is: SQRT(10^2 + 10^2 + 10^2 + 10^2 + 10^2 + 10^2 + 10^2 + 10^2 + 10^2 + 10^2) = 32.

Barnard’s Loop

When I was a kid, Barnard’s Loop was something that I saw on star charts, but it seemed so hopelessly dim, I never expected to actually see it.  And even when I started CCD imaging, it was still a somewhat elusive object: too large to capture unless you used a wide-angle lens, and even then you wouldn’t get decent resolution.  But the combination of a full-frame sensor and a very fast telephoto lens turns out to frame it nicely.

This image obviously has more in it than Barnard’s Loop.  M42/43, the Flame Nebula, the Horsehead Nebula, and M78 all sit nestled within the Loop.  But more interestingly for me, you can start to see the overall Orion Molecular Cloud complex in there: all the dim tendrils that connect each of these objects, some glowing, some blocking the view of the glow.  I regret stopping the lens down to f/2.8 now, as perhaps I would have captured more of the overall cloud that way.  I’d go back and retake the shot if I weren’t having so much fun with this new lens on other targets (and if I hadn’t spent five hours processing this one).  But I’ll consider this a success, as it’s another childhood dream accomplished.

(This image is reduced to 25% of full size, as the 6D’s output is over 20 megapixels.)

Image data:

• Exposures: 81×2 min at ISO800 – total exposure time:  2h 42m
• Telescope: Samyang 135 mm f/2 lens at f/2.8 (reviewed here)
• Camera: Canon 6D (modified) with Astronomik CLS clip-in filter
• Mount: Takahashi EM200
• Guiding: Orion Starshoot, guided using PHD2
• Conditions:  fair transparency, calm winds
• Processing: DeepSkyStacker -> PixInsight -> Photoshop
• Date: Feb 28, 2016

 

Review: Samyang 135 mm f/2 Astrograph

By calling the Samyang 135 mm f/2 lens an astrograph in the title, I’m giving away a bit of the conclusion, so let me just state the conclusions up front: I found this lens to be sharp from corner to corner with a reasonably flat field across a full-frame sensor. This is better performance than all but the best prime telephoto lenses, and also better than many telescopes I’ve owned claiming to be astrographs. Even more impressive is the fact that it accomplishes this at a focal ratio four to eight times faster than “fast” refractors. Finally, it’s hard to beat the price: currently just over $500.

While the performance was adequate at f/2, I found that stopping down the lens one full stop to f/2.8 improved sharpness. This is true of any lens, and even stopped to f/2.8, that’s still four times the light gathered per sensor area than an f/5.6 telescope. It’s easy to forget how fast this is, but my first night using the lens reminded me. My usual telescopes are two f/5 William Optics Star 71s and a Takahashi FSQ-106ED, also f/5. I usually shoot narrowband exposures of 20 minutes with these. So the combination of broadband and f/2.8 put me in the realm of 30 to 120 second exposures—anything longer at ISO 800 overexposed the stars.

The infinity focus point is about 2 mm left of the mark on the lens barrel, so you’ll have to carefully dial in focus. There isn’t much tolerance for error at such fast focal ratios, as the zone of focus is very narrow.

Vignetting is substantial in the corners, but it is more reasonable if you move slightly inward.  For very fast optics, this is typical, though it does lead to lower SNR toward the corners. I was able to keep the full frame images without cropping by using good flat frames, but this is essential.

Master Flat created from 33 pictures (Average)

The quick 99×1 minute image below of the Rosette Nebula area gives you a sense of how wide the view is with a Canon 6D. In the center is the Christmas Tree/Foxfur/Cone Nebula area, with huge dark nebula Barnard 37 prominent. This was taken without a CLS filter, so light pollution prevented me from adequately revealing the Foxfur nebula well. The Rosette Nebula shines brightly to the left, though. (Note that this image is reduced to 25% of the actual image resolution.)

As you can see from the full resolution close-ups below, the lens is impressively sharp across the Canon 6D’s entire field of view, with very minimal distortion even in the extreme corners.

The 9-blade diaphragm of the Samyang results in a pleasing radiant around bright stars, but the lens does exhibit some internal reflections.

I look forward to using this lens as my (very) widefield astrograph. Depending on your sensor size, the ideal targets for this lens will vary, but I’m looking forward to shooting:

• The Orion Molecular Cloud Complex
• IC2177 and Thor’s Helmet area
• The California Nebula to Pleiades area
• Orion’s Head/ Meissa Nebula
• Heart and Soul Nebulae area
• The Rho Ophiuchi area
• Cygnus
• The IC405/IC410 area
• Taurus Molecular Cloud
• The Milky Way’s Pipe nebula region
• Sagittarius

After complex mosaics and multi-night narrowband CCD projects, it’s a joy to throw a simple setup like this onto the mount to grab bright widefield images in a few hours.

Pros:

• Fast focal ratio
• Sharpness
• Flatness of field
• Price (currently ~$529 USD)

Cons:

• Some internal reflections
• Limited targets available for this focal length
• Will require adapter to fit CCD cameras

Orion Rising Over Courthouse Butte

Sedona, Arizona has the clearest, darkest skies I may ever see (anywhere near civilization at least).  Who knew there was a winter Milky Way visible too?!  Not this suburbanite.

I got one clear night to test out both my new Samyang 14mm lens and the iOptron SkyTracker.  While this image is not the best example of the SkyTracker’s abilities, since I misaligned it, the foreground framing was better than the other shots I took.  So this is the one I chose to process first.

Image data:

• Exposures:  sky:  20×30 seconds, foreground: 1×30 seconds
• Telescope: Samyang 14mm f/2.8 lens at f/4
• Cameras: Canon 6D (modified)
• Mount: iOptron SkyTracker
• Guiding: none
• Conditions:  excellent transparency, passing clouds
• Processing: DeepSkyStacker -> PixInsight -> Photoshop
• Date: Jan 29, 2016

Cocoon Nebula (IC5146) Widefield

I used the snow day here in the northeast to get started on the backlog of raw data from the fall that I haven’t processed.  This is the Cocoon Nebula, with its dark nebula friend, Barnard 168.

I actually took a full night’s worth of H-alpha data, but decided to use only the RGB data here, as a slight misalignment of the telescope shooting the H-alpha would have required a different cropping of the image.

Image data:

• Exposures:  15×10 min R, G; 18×10 min B (2×2 binning) – total exposure time:  8 hours
• Telescope: William Optics Star71 (360mm f/5)
• Cameras: SBIG ST-8300M
• Mount: Takahashi EM200
• Guiding: QHY 5L-II mono, guided using PHD2
• Conditions:  good transparency, calm winds
• Processing: DeepSkyStacker -> PixInsight -> Photoshop
• Date: Sep 14 and 17, 2015

Evaluating the full-frame performance of the William Optics Star71

I’m excited to start imaging with my new Canon EOS 6D.  Having a full-frame chip will allow some very widefield shots that would require mosaics with a 4/3 sensor, like the KAF-8300 cameras I use most of the time.  Since conditions were less than ideal, I used the first couple of nights out to run some tests.  First up is a test of the 6D with the Star71.

The obvious target:  M42.  Below is a very brief exposure (17 min total, in 15s subexposures).

That is a very wide field.  5.8 x 3.8 degrees.  I didn’t even intend to include the Horsehead Nebula when I pointed the mount at M42, but the field is so wide, I accidentally captured most of it.

Are the stars sharp out to the corners?  Yes.  The image below is a crop of 100 pixel squares from each corner of the above image.  No star reduction was done in any of these images. The performance is really good.  A little distortion on the right side, but quite tolerable.

What about vignetting?  I estimate less than 10% light falloff between the center and the corners from the flat frame analysis below (the image is highly stretched to reveal vignetting).  Note that there is a dark band across the bottom.  This was consistent across my images, and I’m not sure of the source, but I suspect something to do with dcraw (this image was imported into PixInsight, which calls dcraw for conversion).  DeepSkyStacker seemed to have trouble with some of the 6D’s images too.

The 6D and Star71 are a good pair, and it’s nice to have a DSLR again for simple one-shot color imaging, especially for wide fields.  Once I get some adapters, I look forward to running the same test with the Takahashi FSQ-106ED.