August « 2017 « Andrea Nicole Photography & Web Design




Photographing the Andromeda Galaxy

Clad in the light of a million stars, I’ll never forget the first time I saw it. Just a hop away from Cassiopeia, our nearest galactic neighbor lives amidst a busy summer sky, competing for attention with the magnificent core of the Milky Way. But for those who seek out its beauty, it is every bit as breathtaking.


While in possession of the 600mm Canon lens I used for the eclipse, I sought that beauty for real this time (instead of my accidental capture a few years ago while doing wide-field of the Milky Way).

Without a tracking mount, I knew I’d have my work cut out for me; but the complexity of the situation would prove no match for sheer determination. My task involved calculating the maximum exposure time I could get away with before star trails became a problem (which at a focal length of 600mm was going to be really short) and relying on: a) tracking the galaxy manually by independently adjusting the azimuth and altitude positions of the camera every few minutes, and b) taking a massive number of short exposures that I could later stack in Deep Sky Stacker to increase apparent exposure length.

Light pollution is a perennial challenge faced by the astrophotographer, its lament only exceeded by that of clouds. So I packed up my gear and set out for darker skies. Using my oft-referenced Dark Sky Finder, I ended up in a green location, which although not ideal, was the best option given the circumstances. Conditions were further worsened by a large, uncontained wildfire near the area, creating significant air pollution. But alas.

After getting all the gear set up, the first task is locating the photographic subject. Of course, there are a million ways to skin this cat. For Andromeda, I know where it is relative to the constellation of Cassiopeia, so I just located that first and then star-hopped to Andromeda. You can also try the Google Sky Maps app, with which I’ve had variable success; it can be useful if the compass on your phone is perfectly calibrated, but for me, old-school star hopping has always just worked better.


Stellarium, a free, open-source software program that I rely on heavily for planning my astrophotography outings


On a side note, if you do happen to be doing wide field, in addition to Stellarium, Google Earth can be an extraordinarily powerful tool for planning your shots, by punching in the locations you’re considering and checking them out in three dimensions, to search for the ideal foreground.



View of Prusik Peak in Google Earth

For starters, I calculated my maximum exposure time, based on the formula I laid out in my wide field astrophotography post. I am now using a full-frame camera (6D!), so the formula was:

Max exposure = 600/focal length.

So, with a 600mm lens, the calculation is pretty simple – 1 second. But I like to live dangerously with my exposure times, so I used this as a mere guideline around which to shoot.

What I actually did

  • Light frames: 823
  • ISO range: 6400 – 25600
  • Aperture: f/4
  • Exposure range: 1/4 – 2 seconds
  • Cumulative exposure: 13.5 minutes
  • Dark frames: 99
  • Bias frames: 95

I can’t recall how many actual photos I ended up taking of the galaxy, but after going through every single one individually to evaluate quality, I ended up with 823 usable light frames. I managed to push some of the exposures to 2 seconds, but notably these were extremely hit-or-miss in their usability. The aperture was f/4 for all shots, which is wide open for this lens, and there were happily no problems with coma distortion. I also took 95 bias frames and 99 dark frames to add into the stack, as this strategy can reduce noise in the final image.

Dark and bias frames

If you are doing any kind of deep space astrophotography, you need to know about dark and bias frames because they can be helpful in creating a quality final image.

Dark frames are captured by taking images with the lens cap on at the same ISO, exposure length and ambient temperature you took your light frames at. Stacking these images with your light frames essentially “cancels out” the thermal and electronic noise generated by the camera. Since I shot at so many different exposures and ISOs, I ended up with a lot of dark frames.

The purpose of the bias frames is to basically zero out all the pixels, so they all have equal starting color values. Bias frames are also captured with the lens cap on and at the same ISO and ambient temperature, but at the shortest exposure time allowed by the camera.

Post-processing

My initial image out of Deep Sky Stacker had a distinctive red hue, I’m assuming secondary to airglow, given that the night was moonless and I was under relatively dark skies. This is really the first time I’ve so prominently captured airglow; usually, I end up with more green tint because of the Bayer filter in DLSRs that generally captures twice as much green as red or blue, coupled with the ambient yellow-green haze from light pollution. Anyway, I popped this into Photoshop and did a variety of post-processing maneuvers, mostly using Curves, which worked nicely and produced the above final image.

My post-processing technique is usually fairly straightforward. I essentially set the white balance in the camera to “daylight”, and once I take my image from Deep Sky Stacker into Photoshop, I open curves and adjust each individual color channel by moving the lower left slider to match up with the beginning of its respective color peak on the histogram.


Beyond that, I generally make a few adjustments to the RBG Curves line to increase contrast, and occasionally do some work with Levels. I usually make a pass through a noise-reducing program. I don’t have anything specific to astrophotography; I use Topaz DeNoise, because that just happens to be the noise-reducing software I have. I think there are some programs that are better for astrophotography, but I’ve never used them.

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Solar Eclipse


Baily’s Beads, just moments before totality

It finally happened. After many long years of seemingly inexhaustible patience, the culmination of astronomical glory passed instantaneously like a blip in time, and yet for that two minutes and nine seconds, time stood still.

Without a firm plan, I filled my car with enough gas, food and water to go for days without stopping, and a 600mm f/4 lens with a solar filter strapped to a Canon 6D I purchased the week before. I set out on Saturday evening in the general direction of eastern Oregon, to organically find the armageddon that apparently awaited me.

Night fell as I drove over the rolling hills of eastern Washington, the sky pitch black and speckled with millions of faints stars, on account of the moon’s absence.


My campsite along the Snake River

The next day, I came upon a peaceful spot along the gentle curves of the Snake River, as it hugged the Oregon-Idaho border, and decided to setup camp. Wispy clouds painted the sky, and I silently scorned their presence.

Sunday night was sleepless, in part due to excitement and last-minute planning, but maybe more to the fact that I was in possession of a 600mm lens and Andromeda was visible high in the night sky, thanks to late dissipation of the maligned cloud layer. Either way, the following morning, my tired eyes welcomed the sunrise, and I smiled as light poured across the landscape from a crystal clear sky, knowing the moon was quietly stalking the sun.

The day had arrived. And I was ready.


I couldn’t help taking multiple pictures with the beast lens

Early that morning, people began filtering into the surrounding areas en masse. My spot was secure though, and I waited patiently for the moon to encroach upon the sun.

Following first contact, I watched as the moon covered each sunspot in sequence. The silhouette of the sun was gradually reduced to a crescent, the air temperature dropped and the quality of light dimmed to an eerie dusk.


Partial eclipse

And then totality began.

Darkness fell and a cold breeze chilled the dry summer air. I looked up to see the moon ablaze, surrounded by an enormous ring of purple-blue fire, black as night in the center. Stars dotted the deep blue sky, Regulus closely flanking the hiding sun.


Totality with inner corona

They tell me totality was two minutes and nine seconds. But I don’t believe them. I was armed with a plan to photographically capture the eclipse in all its magnificence, but this deteriorated quickly when I couldn’t bring myself to look away from its ethereal beauty.

After what seemed on the scale of nanoseconds, the sun began to emerge from behind the moon and bathe unsuspecting onlookers with an overwhelming tsunami of light.


The Diamond Ring phenomenon with chromosphere and some prominences at the end of totality

Indeed, the mysterious midday nightfall and the bright blue arms of the sun’s corona reaching outward toward the universe were among the most hauntingly beautiful things I’ve ever seen.

TECHNICAL DETAILS

Successfully photographing an eclipse requires considerable planning and attention to detail, as things unfold quite rapidly around totality.


The eclipse-mobile command station

Timing

Certain aspects of a total solar eclipse happen at fairly precise times, so this part requires planning up front. Upon arriving at my location along the Snake River, I punched my GPS coordinates into an eclipse calculator to generate a timetable for the eclipse, most importantly details surrounding totality. I was also armed with a clock synced reasonably well with atomic time, to afford me the precision necessary for some of the shots I wanted to get.

Focusing

Focusing on any object in space can be tricky and autofocus usually fails. There are a few options to handle this:

  1. If your lens has a focus indicator that allows you to manually focus to infinity, just set your focus to infinity, and the results will probably be reasonably good.
  2. If you happen to be shooting with a camera that has Live View capabilities, as the 6D does, you can turn on Live View, set the magnification to 10x, and choose a part of your scene that is easy to focus on manually (e.g. sunspots). This is what I did.
  3. If you have neither of the above options, you can use autofocus and point your camera at something in the landscape located at least 100 yards away, then once you’ve auto-focused, click the lens over the manual focus and don’t touch the focus ring. This is essentially equivalent to focusing to infinity.

Infinity focus indicator on a Canon lens

Settings

  1. Partial Phases: these are generally easy to photograph, and I did so with a solar filter at an exposure of 1/2,500, f/5.6 and ISO of 100.
  2. Totality: there are a couple of phenomena that occur in the totality and peri-totality timeframe that require precise planning. All of these shots are taken without a solar filter, meaning you will remove/replace your solar filter approximately 30 seconds before and after totality.
    • Diamond Ring: this occurs about 10 seconds prior to and following totality. For this shot, I used an exposure of 1/320 sec, f/5.6 and ISO 100.
    • Baily’s Beads: these are created by the last gleam of sunlight shining through the valleys between mountains on the limb of the moon and they appear as little beads of light. This phenomenon occurs approximately 3 seconds before and after totality, and is generally photographed immediately after/before the Diamond Ring. For this shot, I used 1/4,000 sec exposure, f/5.6 and ISO 100.
    • Chromosphere: this is the part of the sun’s atmosphere that is directly above the photosphere and in images it appears as bright red-pink in color. For this, I used the same settings as for Baily’s Beads.
    • Prominences: These are enormous red-pink plasma ejections along magnetic field lines from the surface of the sun. I captured these again with the range of settings used for Baily’s Beads and the Diamond Ring.
    • Corona: this is the massive field of plasma ejections extending millions of kilometers from the surface of the sun, responsible for the appearance of blue fire engulfing the moon during totality. The brightness of the corona is a function of the distance from the sun, so different settings are required to capture different parts of the corona. For example, inner corona can be captured with a rather short exposure because it is quite bright. The middle and outer corona are much more faint and require longer exposures to capture. I successfully captured inner corona, using an exposure of 1/500 sec, with the same settings as above for aperture and ISO. I failed at capturing mid and outer corona because this was the period of time where I just couldn’t stop staring at it long enough to adjust my exposure.

Totality ending before I was ready

I waited 23 years for this eclipse, ever since seeing the annular eclipse of 1994. It was worth every second of the wait. That hypnotic blue fire was otherworldly, mesmerizing and unifying, epitomizing the endlessness and depth of beauty in the universe.

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