Light is Still the Key

 

In any kind of photography, light is the key ingredient. It’s not so much the quantity of light that is important, it is the quality of that light. When you view one of those amazing nature photographs taken by one of the amazing nature photographers what stands out the most is how they were able to use light to great effect. Light is the most important element when it comes to defining and creating a great photograph and this holds true even for astrophotography. The difference between a great astrophotography image and a generic landscape is the quality of light is almost always inherent in the night sky, it’s just really, really faint. That factor alone is what makes night sky photography a challenge, but one worth attempting.  

Photographing the night sky comes with all kinds of technical challenges, but even novice photographers possess most of the basic skills required to capture a fantastic shot of the Milky Way on a clear dark night. If they do lack anything, it is a lack of understanding about the night sky itself. Even though light is the key, composition plays off that key and without a clear and organized composition, even a wonderful night sky event will often fall short. 

I find myself expressing jealous feeling toward those who have the opportunity to photograph the night sky from a vantage point out west with its wonderful dark sky opportunities. It is there one can find amazing foreground objects to enhance the composition which is embellished by the brightness of the night sky. In Kentucky we have to contend with a lot of hazy and often overcast skies not to mention the abundance of light pollution. Even so, with a little research one can find a suitable location. Then it becomes a matter of being willing to be there and a little luck with the timing of a dark sky with a clear night. 

For night sky photography, the absence of light is what shapes the image. It is those dark areas that add character and drama. Break up those dark areas with glowing nebulas and star light and your image begins to glow with a resonance that is out of  this world, literally.

 

Capturing a Deep Sky Object

As I thumbed through the pages of the Backyard Astronomers handbook each image exploded off the pages with a brilliant flavor. I read about how the Hubble Space Telescope changed our view of the universe and I gazed at images that were clear and crisp and bright. I have also watched various video programs about visually exploring the wonders of the universe and how magical and exotic those parts of creation can be. These views were taken with expensive instruments so sensitive that the most distant reaches and faintest measures of light can be imaged. They are incredible and inspiring.

Orion Nebula - Where stars are born

Amateur astronomers have available today a myriad of small but powerful telescopes that removes much of the mystery behind navigating the night sky. Many of these are affordable, some maybe not so affordable except to the most die hard. They are capable of revealing and tracking a tremendous array of night sky objects using their computerized tracking software and drives. For those of us who must live on a tighter budget, well about all we can do is to sigh with envy and appreciate the contribution these amateur level instruments provide. But all is not lost.

The past year or so I began photographing the night sky and following the work of others who produce amazing images. I’ve also read about and followed several amateur astronomers who photograph deep sky object using their sophisticated computer tracking telescopes. Some of the results they obtain are truly amazing. This season, I began to explore how to capture some of the more easily found deep sky objects. What I discovered is that even without an high dollar computerized astronomical instrument, you can capture some incredible images using simple homebuilt tracking equipment and basic photographic cameras and lenses.

In a previous blog entry, I wrote about building a manually operated barndoor tracker. For wider area photographs, this manually operated device worked very well, but in order to photograph deep sky objects, you need to have a motorized version that tracks the sky more smoothly. The previous image shown above and the one below illustrate the results that can be obtained by adding a simple 1 RPM motor to the tracker. Using this setup and with some careful identification, I’ve been able to track and photograph a few deep sky objects. The easiest of these is Orion’s Nebula in the constellation Orion.

 

 

In the northern hemisphere Orion is primarily a winter constellation and the nebula located in Sword of the Orion’s belt is easily seen even with the naked eye or with a pair of binoculars. Last winter I attached my 500mm lens to the tracker and pointed it toward the nebula to see what would happen. Once I had the tracker properly aligned as discussed in that previous blog post, I experimented with the exposures and the tracking. What resulted far exceeded what I expected.

One of the techniques more serious photographers use to capture deep sky objects is what is called stacking. This technique involves taking a series of images (several hundred in some cases) using relatively short exposure times and then building the image one layer/stack at a time using software written for such techniques. If you know how to do it and are a whiz kid in Photoshop, you can indeed create some amazing images. The images I took were the result of a single image that was slightly tweaked in Photoshop. The result obtained were pretty good and much easier to do.

First I setup the camera at 3200 ISO and opened the aperture all the way, in this instance f/6.3 at 500mm. I took a short test shot to verify I had the nebula located in the view finder then I turned on the motor drive and allowed it to run for a few seconds to dampen any startup vibrations. Using a cable release I fired off a series of exposures ranging from a few seconds upwards to 30 seconds and over a minute. What I discovered was that the 20 second shot provided the best combination of detail, color, and depth. With a bit of cropping, a little tweak in Photoshop to boost the saturation, dampen the star glare hovering inside the nebula, and making sure the sky was black, the image materialized into one where the lacy wisps of glowing gases and starlight became visible with good definition and clarity.

The clarity of the image proved just how accurately the motorized barn door tracker worked. Total out of pocket cost to build it was less than $40.00 using materials already on hand, the largest expense being the 1rpm motor that cost about $25.00. Not everyone has a 500mm lens laying around to use, but many people do have 70 – 200 or 75 – 300 lenses. These will work almost as well, but may not crop as tightly.

Another deep sky object that is relatively easy to find is the nearby galaxy Andromeda, also known as M31. Andromeda is the closest next galaxy to our own Milky Way Galaxy, but it is considerably larger, at least twice the size, but is shaped similar to our own as a magnificent spiral. Andromeda is actually moving rapidly toward us and in a few billion or so years it will collide with the Milky Way and forever change the shape of both of them. Andromeda is visible by mid-summer above the northeastern horizon and continues to rise higher into the night sky as the summer progresses and if you are willing to stay out until the wee-hours of the morning you will be able to find it hovering high enough in the sky to get above the horizon light polution glare. It is located oddly enough in the constellation Andromeda and by using a star chart and some experimenting, you should be able to find it by late June or early July around midnight about 30 degrees or so above the horizon in the middle latitudes of North America. It is surprisingly quite a large object in the night sky and is just visible as a dim smudge to the naked eye on a clear dark evening. The light gathering ability of the camera will capture the dim light rather nicely.

Andromeda hovers in the summer sky

 

The photographing techniques are the same as mentioned above and it can become one of the most exciting objects to photograph. I'm still working on obtaining a really clear image, but I have managed to capture a few decent images. It is much dimmer than the Orion Nebula and this requires a little longer exposure, and the dictates a much tighter tolerance on the alignment of the tracker.

Capturing deep sky objects are well within the capabilities of the average photographer and certainly is worth the effort. Give it a try, and along the way you might discover something exciting about the night sky.

 

Keith