Anatomy of an Image – Mackinac Bridge and Comet NEOWISE

Deepscape astrophotography is quite polarizing. You are attempting to record a scene in which your eye cannot, or barely can, see. As a result, the vast majority of these types of shots do require multiple exposures, tracking, stacking, and blending to bring out the hidden details. That is especially true when shooting into light pollution or with deepscape subjects. I wanted to preface the article this way because if you are uncomfortable with blending shots to create a final composition, then deepscape astrophotography may not be for you. It DOES NOT mean they are not real scenes. They absolutely are. We are working with the limitations of the gear to create the highest quality image possible.

July proved to be a month to redeem the rest of the year’s rather insane chain of events. A comet became observable to the entire northern hemisphere. Comet NEOWISE would go on beyond just a beautiful binocular object. This celestial visitor was visible to the naked eye – it was dazzling the world over! Soon the entire Astrophotography and Nightscaper community pulled their collective camera together to record this comet from all over the world. A wonderful reminder about how celestial events can help us heal. I digress, though.

“DeepScapes” and Telephoto Lens Compression

The moment I first heard about the comet, I sprung into action to find memorable landmarks to photograph with it. I also realized that this would be a fantastic opportunity to plan a few deepscape images around. An excellent in-depth article on deepscape astrophotography is here on MilkyWayPhotographers:

Deepscapes: Leave the Wide-Angle Lens at Home

Deepscapes are similar to the “big moon” photos. It creates a compressed field of view, exaggerating the main subject with a secondary one. The result is one that suspends reality and brings those heavenly objects close to home. I REALLY wanted one with the comet!

What causes this rather jarring, yet captivating, effect? A few things. I cover this a bit in a previous article on photographing the Moon. To recap, I’ll pull into this article what I wrote in the Moon one. The first phenomenon is an optical illusion known as the Ebbinghaus illusion.

How does it work? Two circles of identical size are placed near to each other – large circles surround one while small circles surround the other. This juxtaposition creates the illusion that the central circle surrounded by large circles appears smaller than the central circle surrounded by small circles. Yet, they are the same size.

There are several studies, in addition to the Ebbinghaus illusion, examining why we perceive a Moon, or other objects, on the horizon larger than when they are above the horizon. Some theories stem from binocular vision – as your target subject rises, we lose that reference to a terrestrial object and thus have nothing to compare it to anymore. If you would like to read more on this phenomena, check out this study: https://www.pnas.org/content/97/1/500

Lens Compression

The second aspect is a concept known as “Lens Compression.” A better, correct term for this would be “Focal Length Compression,” as it has nothing to do with the lens, per se. Lens compression is a type of distortion. This phenomenon makes background elements appear much larger and closer than they are. This distortion gets more pronounced as the focal length increases.

While the use of lens compression is popular for portrait photography, it can be shocking when applied to landscapes. Mostly because landscapes are often shot with a wide-angle lens – think about that for a second. When was the last time you photographed a landscape scene with a focal length over – say – 50mm? Flip from a 14mm to a 200mm, and the view is going to look very different!

As I watched comet photos flood the internet, I noted most used the typical wide-angle lenses. People got used to seeing a “small” comet. There were several telephoto shots posted, as well, but not with landscapes incorporated. Without the frame of reference, this doesn’t look out of the ordinary. However, if you couple that telephoto comet view with a landscape foreground – holy cow, what a view! The comet literally fills the entire frame. This effect is the goal of deepscape astrophotography.

More info on lens compression can be found here: https://www.slrlounge.com/lens-compression/

Challenges of Deepscape Astrophotography

Utilizing the longer lenses at night does introduce a few new problems. The biggest of which is how quick star trailing happens. Once you creep towards 200mm, this will happen in a second or less. You almost always will need to use a star tracker of some sort. The exception is if you want to do star trail shots, of course! Using a tracker means that you can no longer shoot single exposures if you have any landscape foreground.

Composites

This is where the photography community often fights like cats and dogs over what’s a composite image and what isn’t. Generally speaking, if you don’t move your tripod and shoot the exact same scene from the same night, these are blends and not composites.

Yes, I am aware of the actual definition of a composite. However, in this case, you are working with the limitations of the gear. You are NOT taking elements from a different location, day, scene, or Google image search and adding them into your final composition. THAT is a composite. I strive for an accurate representation of the scene as it was. These are blended shots. Otherwise, why would I stay up all night waiting for that perfect alignment?

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Focusing and Shake

Next up are focus and camera shake. Telephoto lenses are harder to nail focus with at night. Some of this is that when zoomed in, any slight touch or breeze introduces shake. That is important to remember overall. Once you start hitting focal lengths of 600mm, you’ll find yourself having to use mirror-lockup on the DLSRS, to help alleviate the camera shake. Be sure to have a good and preferably wireless remote to trigger the shutter. The less actual touching of the camera, the better!

Framing at Night

Finally, it is framing your scene. During the daytime, this is less apparent since you can see everything. Heck, I’ve never paid attention to how little you have to move a telephoto shot to make a big difference in the scene’s framing. When making shooting deepscape astrophotography, it’ll smack you in the face! You do not need to move the camera much at all to change the framing completely! That is why people that shoot DSO have those nifty Go-To telescope mounts! Trying to find an object that is millions of miles away in a sea of stars at 200+mm is next to impossible. Ha!

Also, depending on the weight of the gear, a counterweight may be needed. With the Nikon Z6 and Nikkor 70-200mm, I haven’t needed one. If you cannot get a clean shot with pinpoint stars and your polar alignment is good, look to the weight balance.

Plan Your Photo

Shots like these require much more careful planning since you are dealing with a small field of view. Then add in the ever-changing position of a comet, and it becomes even more challenging. Luckily, there are tools available online and through cell phone apps to help pre-visualize your shot.

The Sky Live

Several planetarium programs are available at your fingertips. Stellarium is extremely popular and available on both desktop and mobile devices. However, I kept hearing mixed messages regarding adding the new comet to the program. Some said it was free, and others said it was a paid premium. I ended up using The Sky Live online planetarium to plan a few shots. It’s free, easy to use, and best of all – web-based. How accurate is it? Enough to allow me to get the photograph I was after!

That is when I went AWOL from all the media outlets! Most of the media articles on Comet NEOWISE stated that it was only visible for a few hours after sunset after July 15th (It was a dawn object prior). However, if you were in a northern latitude – say 44 degrees north or above – NEOWISE could be visible ALL NIGHT. Starting around July 12th, I was able to see the comet skim the horizon before moving back up from Wisconsin’s Door County. As the nights progressed, the comet would continue to stay higher and higher above the horizon.

Another misconception portrayed by the media was the direction of both the tail and for viewing. Many stated it was only visible a few hours after sunset. During the evening, NEOWISE was in the northwestern sky. As the night progressed, the comet moved to the north before moving northeast as the sun rose. That brings me back to the plan at hand.

The Mackinac Bridge connects Michigan’s Upper and Lower Peninsulas. It faces a north or south direction, depending on what side you are on. I wanted the comet framed by the towers, which are north of Mackinaw City. According to The Sky Live, on July 20th, around 3:12 am, NEOWISE would squarely to the north. One must also take into consideration the altitude. I didn’t want the comet below the bridge or too high above it. There would only be a handful of days where this alignment was the best.

PlanIt! Pro

Now that we know where Comet NEOWISE was going to be, we need to figure out if the rest of the scene will work. Enter PlanIt! Pro. This fantastic tool lets you pre-visualize a shot with astonishing accuracy. PlanIt features constellation overlays, which is invaluable. Star charts and constellations helped locate the comet. NEOWISE liked to hang out in the Big Dipper, which is nice because that is a very easy constellation to find. Even in a Bortle 9 zone, you can see the Big Dipper.

The first step is to load your location into the app. You can do this by a search feature, or just pinning the GPS-based dot. From here, move the field of view (shown in green) to where you hope to shoot. Changing the focal length affects your field of view. Initially, I usually kept it around 50mm, as it was easier to spot targets. Then I switched to the desired focal length to fine-tune the view.

To further visualize the shot, you can bring up the Virtual Reality mode. With constellations turned on, this helps you pinpoint where your subject will be relative to the horizon and if it’s even in your view! The compass, along the bottom of the VR view, will help orient yourself in the direction of shooting. The app also will download elevation maps, so you can see if there’s a mountain in your way. I was in Michigan, so there are very few mountains to worry about! Ha!

Image Acquisition

Alright – the time has come! You have waited up all night for this moment. The moment where – the comet in this case – graces your frame! This is the most critical part of your imaging session, as you want your main subject to be as close to the plan as possible.

I fired off six 1.5 min tracked shots as the comet moved across the bridge’s towers. Seeing the faint, icy snowball show up on the back of the camera was nothing short of amazing! Even looking through the light of the bridge, there it was, tail and all! I then shot the untracked foreground shot, which I always shoot more than one, just in case. This night was quite windy, so I had several unusable images due to camera shake. You can shoot foreground before tracking, too. It’s entirely up to you.

Once you are happy with your tracked shots, concentrate on the foreground. Or if you already captured it, you’re done! I make it a habit to go back and check focus on the images, and for any issues with camera shake and the like.

The Magic of Stacking – Even with Tracked Shots

It is entirely feasible to use the two above shots to create a final blended shot. However, if you are anything like me and you want the maximum amount of detail from these kinds of lighting conditions, you’ll want to stack those tracked shots in a program like Deep Sky Stacker for Macs or Sequator for PC. These programs were developed for – you guessed it – deep-sky imaging. All those beautiful and pretty photos of nebulae and galaxies benefit from many images stacked together. The more data you have, the more the computer can extract! Lately, a few of us have been combining the art of deep-sky imaging with landscape elements to create these otherworldly compositions.

In the cropped image above, you can easily see the detail from the tail! Six tracked images netted a huge gain in data through the lights! Pretty amazing, right? No need to slap in a comet from somewhere else!

Putting it All Together

Here is where the magic happens! Initial adjustments, such as white balance and exposure, are done in Lightroom or Adobe Camera RAW. Matching the color casts and exposure between the shots will make your life easier – trust me! Once satisfied, save out the individual files. The actual number of files needed depends on the situation. If you needed to focus stack, you’d have more to deal with, for example.

Open the files in Photoshop. You can either open them all individually or use Photoshop’s “Load Files into Stack” script. The latter saves you some time copying and pasting them over to the master file. Nine times out of ten, the next step will be aligning the layers. Believe it or not, the camera does move ever so slightly – even when taking same the same shot over and over. There are a few ways to deal with this, too. Manually, with the transform tool, or the “Align layers” script. (EDIT > AUTO-ALIGN LAYERS)

Once aligned, mask the tracked sky shot into the foreground. All you do is add a mask to the sky layer and then mask out the unwanted blurry foreground. Voila! You have created an image representative to the scene, but with much more detail, less noise, and better overall quality. Now, further adjustments may be needed, such as matching the brightness of the layers or fixing a slightly different color cast. Also, depending on how complex the foreground is, you may need to spend a crazy amount of time masking trees. Ask me how I know!

Conclusion

As astrophotography becomes more accessible to everyone, pushing the envelope of what’s possible follows suit. What started as single image exposures turned into blue hour blends, stacking, and focus stacking at night. Then tracking and experimenting with long lenses. Now many use software developed for astronomy for wide-field Milky Way landscapes. The results are spectacular, in my honest opinion! I hope you find some inspiration here to experiment with longer lenses and create some deepscape astrophotography for yourself!

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