More astrophotography

Yesterday marked the 14th rendition of the annual Shreve Migration Sensation. I was flattered to be asked back to speak; this go-round my topic was the wetlands of Wayne County. The SMS takes place in the village of Shreve, population about 1,500. During SMS, that number swells to about 3,000. It's a big event, and great for the local economy. Thanks to everyone who organizes the Sensation, and puts in the hard work to make it happen.

As you may have learned, predicting weather and atmospheric phenomena is hardly an exact science. Knowing that I'd be in Wayne County until late in the day, I kept an eye on various forecasts, which were calling for a clear, cloud-free Saturday evening. That was good news, as I could turn my camera to the stars once again. Didn't happen, at least initially - clouds rolled in and blanked out the evening's stars. After shooting waterfowl (with camera) in one of the marshes until dusk settled thoroughly in, I headed for home. About half an hour into the trip, the cloud cover was swept aside and the night sky glittered with stars. I turned around, and headed quickly back to one of the most remote, darkest corners of the massive Killbuck Marsh that I knew.

By the time I got there, rigged the camera, donned boots, and waded back to a good spot, it was thoroughly dark. To my south, the sky seemed plenty dark, but for star shooting one generally wants to point the camera north, towards the North Star, or Polaris. This celestial body is in line with the axis of Earth, and does not appear to rotate and thus provides an excellent reference for dramatic long exposure night shots.

What I did not anticipate was the high degree of light pollution, even in this seemingly remote spot. Even though it is about eight miles to the north, the city of Wooster put up such a glare of night light such as to ruin any astrophotography opportunities. For this shot, the camera was set to take continuous 30-second exposures, and 84 of those are stitched together to make the image. As the camera labored away, and I kicked around the darkened marsh, I realized that the light was probably going to kill the shot. And it did. Very few stars are visible, and the light makes it appear is if the sun is rising. There wasn't much I could to do to mitigate for the light by adjusting camera settings, or in post-processing.

I figured I'd let the shot play out, though, as even if bad it would be a learning experience. After the 45 minute exposure was complete, I packed everything up and headed for another, darker spot that was (sort of) on the way home.

Ah! Much better! This hour-long series of 108 30-second exposures was made from a remote spot near Mohican State Forest in Ashland County. Even though it is far darker than the previous locale, plenty of light still bleeds through courtesy of the distant cities of Loudonville, and probably Ashland. However, the distant glow creates an interesting backdrop that I don't altogether mind.

While this image is a composite of 108 shots stitched together with editing software, I have done very little else post-processing other than to slightly lighten the image to allow the trees in the foreground to show better. The dotted line going through the shot is from an airplane passing through; yet another form of nighttime clutter that the astrophotographer must deal with.

Other than finding a dark corner of the world, the most challenging aspect of making star trail images is setting up the shot. I have learned that in light-plagued Ohio, using a single very long (half hour to an hour) exposure will not work. Such a lengthy exposure lets in far too much light. Short 30-second bursts is the way to go, and to do that one must mount the camera on a sturdy tripod and activate the shutter with an inexpensive remote cable release. It must have a locking mechanism, so that when the button is depressed and locked, the camera will keep firing shots every 30 seconds until told to quit, or the battery runs out. The lens choice is important. I used Canon's fabulous new 16-35mm f/4 ultrawide angle to make these images. It was set at its widest, 16mm, and focused to infinity. Camera settings are fairly straightforward and the following seems to work pretty well in general. Aperture should be wide open, which as noted is f/4 with this lens. Shutter speed is set to 30 seconds, which is the longest my (most, probably) camera will go without resorting to the "bulb" setting. ISO is critical, and the setting that will require the most onsite tweaking. An ISO between 500 and 800 will probably suit many conditions, and for the image above I settled on ISO 500. It's always best to take several practice shots and assess the quality of star shine on the camera's view finder to dial in ISO.

Probably the trickiest part of setting up a star shot is composing the image. It goes without saying that you're working in very dark conditions, and that makes it tough to accurately assess one's surroundings. I like placing Polaris in or near the left top corner of the image, as the stars appear to rotate around that fixed point. Polaris is clearly visible in this image, framed (almost) perfectly through a gap in some foreground trees. That's one of the major tricks - getting Polaris exactly where you want it in the shot. Looking through the camera's viewfinder and finding an individual star is not easy; in fact it can be impossible to tell which is which. A hugely helpful aid is a "star finder" app for a smart phone. I have one called Sky Guide on my iPhone and it makes life much easier. When held to the sky, it shows a map of the celestial objects in view with prominent ones labeled. By holding that over the top of my camera like a gun sight, I can place Polaris in my camera's field of view with fairly good confidence. It's also important to carefully assess the terrestrial objects and place them in the bottom of the field of view, unless you wish to have a shot that only shows stars. In this case, I liked the way that a large white pine provided a border on the left, and the manner in which the deciduous trees sloped to the right. I did try and pinhole Polaris in that little gap between the pine and other trees, and nearly nailed that. To better assess the location of terrestrial objects and place them appropriately in the image, a flashlight can be used to illuminate things making them easier to find in the camera's view finder.

Once all of this has been done (and you've checked to see that the battery is charged and space is on the memory card) all that remains is to activate the camera shutter. And wait an hour or so, fingers crossed and hoping everything was well set up. If so, the end result can be extraordinary. I look forward to shooting astrophotography in a truly dark environment someday.

Star trails, Version II

In my last post, HERE, I wrote about the making of star trail photos on a rather frosty winter evening. I thought one of the resultant photos, above, was pretty cool. Not bad for a first time effort. Well, I hadn't seen nothin' yet!

I made two hour long exposures, one of which is the photo above. The other one wasn't nearly as good. It was my first effort, and I had allowed too much light to collect via too large of an ISO setting. For the next long-exposure image, I dialed things down and achieved the above result, which was an improvement.

But my research had indicated that making a long series of 30 second exposures would generally yield much better results. The only hitch is that one must digitally stitch the images together, in the order in which they were taken. So, I did indeed take a long series of short exposures, thinking that eventually I'd learn how to sew them all together. Which I did.

See below:

An ENORMOUS improvement on the long single exposure shots! And stitching them together is as easy as pie, thanks to the www.startrails.de website! A German by the name of Achim Schaller (who must be a genius) created software that allows multiple exposures of astrophotography shots to be seamlessly melded together, allowing results such as the above image. Thanks to Toni Hartley for showing me how to work the software, too.

There is no question that the second image is far beyond the single shot exposure, for which I kept the camera's shutter open for a whopping 56 minutes. The second shot was achieved by stitching together a total of 84 images. Each exposure was 30 seconds long, and the camera was set to f/4 (wide open on my 17-40mm Canon lens), at a focal length of 17mm and ISO at 500. As mentioned in the previous post, I set the white balance to tungsten, which gives the night sky a steely blue cast. Photogs shooting in RAW could convert to that white balance mode later, in post-processing, but why not get it right of the can. Of course, to shoot uninterrupted 30 second exposures over the better part of an hour, one must use a remote shutter release that will lock in place, thus constantly tripping the shutter until told to quit.

The reason that the second image is superior is in large part due to the much shorter exposures. There was more ambient light where I made this image than is desirable, from nearby houses, farms, and a few distant cities. Thus, the super long exposure shots harvested tons of light, largely blowing out the stars. The short exposures did not keep the shutter open long enough to collect much light other than that of the targeted stars, thus the much showier photo. After shutting down the camera, all that remains is to stitch all of the images together, and as reported earlier that is pretty simple with good software.

I eagerly await the return of the new moon, hopefully with attendant clear skies. Then, a trip to a truly dark corner of earth will be in order.

A cold sky indeed!

Last night was bitterly cold here in central Ohio, as evidenced by my car's thermometer. Yes, it says -20 F, as in MINUS TWENTY. I knew it was going to be about as cold as I've ever experienced, and I wanted to experience such frigidity. So, after getting home from work last night, I took a nap. Then got up, prepared, and headed out the door around midnight.

The only way that I could think of to try and visually portray the brutally cold temperatures was with sky shots. As is usually the case when the mercury plunges to extreme lows, the sky was bright and clear. I headed north, with a few locales in mind. The goal was to get away from city lights, and find a VERY dark spot, perhaps with some interesting scenery. As I worked north of Delaware, the temperature fell until it hit the reading above, which was at the spot where I made the following image. As an interesting footnote, the extreme cold noticeably effected the way that my car drove. It felt wooden and clunky, and fuel economy dropped to less than half of what it would normally be.

I eventually landed in this remote cemetery, and set up the camera gear to make my first stab at shooting star trail photos. There are essentially two ways to expose the camera to capture the earth's rotation, thus making the stars appear to streak across the sky. One is to take a long series of 30 second exposures (or thereabouts), and later stitch them together with editing software. I did take a long series of such shots, but have not yet stitched them. I'm curious to see the results.

The other technique is to take a VERY long single exposure, which is how this shot was made. I did learn at least two things from this exposure. One, as dark as it seemed, there still was probably too much ambient light pollution from distant cities and towns. And two, a distant farm with its attendant night lights shows up far too well - like the onset of a sunrise. I did not know these things. But I look forward to learning from my errors and trying some more star trail shooting.

This image was made with my Canon 5D Mark III firmly affixed to a tripod. For foreground interest, I placed the cedars along the right side of the image, and that small round tree in the lower lefthand corner. I used the 17-40 f/4 ultra wide angle lens, set to a focal length of 25mm. The aperture was at f/8, and ISO at 100. Here's the kicker - the shutter speed was 56 minutes. To get that long of an exposure, you must use the Bulb setting, and trigger the shutter with a locking remote release. Also, the white balance was set to the "tungsten" setting. That gives the sky a more metallic blue look. Finally, Polaris, or the North Star, is near the top left corner of the image. Focusing on or near this celestial body adds interest, is it seemingly remains stationary while the other stars appear to rotate around it.

All of this worked quite well - I just need to find totally dark areas to shoot star trails, AND wait for one of our rare cloudless nights where the moon is not full.