Tag Archives: stars

Advanced Star Trail Tricks

Published: Oct 11, 2012
Last Update: February 14, 2018 (remove Flash)

I have been playing with Star Trail processing for quite a while.  Ever since I wrote the StarCircleAcademy Stacking Action I’ve been tweaking processing to try different things. Sometimes failure is inevitable, sometimes… well, you’ll see.

First, you may want to look back through my earlier columns on shooting and processing star trails because this is not a primer on star trails – it builds on what I’ve previously written and this is not a good place to try to understand what stacking is.

Second, please understand that I use a variety of tools but almost all of my more successful endeavors end up as layers that are combined in Photoshop (CS5 at the moment).  You could combine your layers in GIMP if you don’t have Photoshop, but you’ll be out of luck if you try to use Lightroom.

Here are my star trail effects:

  1. Smoothee – Averaged sky and/or foreground to reduce the grittiness that sometimes results from brighten stacks. I’ve been espousing this for quite a while. See the Simple Astrophotography Processing Technique.
  2. Blobulous – stars at the beginning (or end) of a trail are made to stand out from the rest of the trail.
  3. Comets – star trails appear to grow brighter and the end of the trail looks like the nucleus of a comet.
  4. Streakers – Like comet only the trails are longer
  5. Blackened – A clever trick removes sky glow from light pollution, the moon, or twilight.

And of course you can make “Blobulous Comets” and “Blobulous Streakers” and “Blackened Smoothee Comets” and more.

Building Blocks

To creatively combine exposures, I usually create the following stacked frames.

  • Dark (Darken in Image Stacker/StarStax)
    The darkest elements emerge – especially the hot pixels
  • Brighten (aka lighten) stack
    The Brightest of everything is present, including hot pixel and more noticeable noise
  • Average
    Contrast is reduced, smoothness increased.
  • Additive (called “Stack” in Image Stacker)
    Hot pixels become really bright.
  • Scaled (called Stack/Average in Image Stacker)
    Allows some increase in brightness but more smoothness, too. Experiment with different divisors.

Normally I create all of these combinations using Image Stacker against my JPG files because it is really easy to do.  I end up with a set of frames something like these although I’ve significantly brightened them so that they are easier to see.

Smoothee

In a Nutshell: Combine the Average stack over the Brighten stack using Normal mode at 45% opacity.

I’ll start with the Smoothee technique since it’s probably the easiest to do and perhaps the easiest to understand.  The problem with “Brightness” (or lighten as it’s called in Photoshop) is that it will also pick up all the hot pixels, and the brightest bits of noise.  Averaging on the other hand tends to smooth out everything except for truly hot pixels since most noise is random. By putting an averaged stack as a layer over the brighten stack and then adjusting the blending modes and opacity you get a smoother sky and foreground.  Exactly what settings to use depend on the images, but surprisingly many of the blending modes for the Average layer work here including Darken, Multiply, Overlay, and Normal. The starting place for Opacity is about 45%.

Hint: You can also use an Additive stack instead of the average stack but usually only the Normal blend mode will work.  For even more fun combine the Additive stack and the Average stack.

For additional smoothness you can also subtract the “Darken Stack” while adjusting the opacity to prevent halos and weirdness.

Blobulous

In a Nutshell: Add one of the single frames more than once.

What do “Blobs” look like? Like this…

“Fat Star” processing.

There are two ways to produce “Blobs”. One way is to add “Comets” to a smoothed star trail. The other is to simply pick an image (usually the last one in the set) and add it in using “Add” or “Screen” mode. To make the blob more pronounced duplicate the last frame so it’s added twice. BUT remember when you add in any single image the hot pixels are going to come out… and even more so if you add an image twice.

Comets and Streakers

These two techniques require some fancy stacking techniques. Fortunately I’ve created an action to do all the fancy stuff.  I’ll be rolling out the action and the explanation to my Photo Manipulation Webinar participants first <NOTE: The Advanced Stacker PLUS action has been released and is available for purchase in our store>.

Oh, here is a peak at what the Comet action looks like:

What's The Point?

And here is what an animation of comets might look like:

Star Rise

 

Settings

I know you’re going to ask so let me save you some typing. Except for the “Comet” image above, all images used in these illustrations were taken during the Ancient Bristlecone Pine Workshop in the Patriarch Grove on White Mountain, East of Bishop, California.

The 34 or so images that I’ve combined in the examples above were all taken with the following settings: Canon 50D, ISO 400, f/3.5, 79 seconds, 10-22mm lens at 15mm.

Coaxing a Meteor into Smiling for your Camera

Nothing is quite as exhilarating – to me at least – as watching the sky explode with “falling stars” or meteors as they are more properly called. Major meteor showers occur through out the year but the most spectacular and reliable showers are the Perseids in August, the Lyrids in April, and the Geminids in December. Other notable showers include the unpredictable Leonids in November. In fact, in November there are quite a few minor meteor showers including the Northern and Southern Taurids, and the Aquarids.

An absolutely brilliant example of well captured meteors can be found in Gary Randall‘s work.

Perseid Meteor Shower over Mount Hood

Photo 1: by Gary Randall. Gary captured 26 meteors over a 3 hour period and realigned them to show their path through the starry sky. 30 second captures f/2.8 ISO 1600 at 11mm on a Nikon D90.

Capturing meteors is much harder than it may seem, however and getting results Like Gary’s is far from a “done deal”. Let’s investigate why and figure out how to successfully capture them.

If you’ve been reading this column for a while you’ve probably already successfully captured a star filled sky. Your camera settings were likely something like this:

ISO 200, f/4, 30 seconds, Focal length 24mm.

There are two components to meteors that make them difficult to capture.

  1. Meteors do not appear in a predictable location in the sky. Indeed all meteors from a particular shower appear to radiate from a single point in the sky, but the meteors streaks may appear anywhere.
  2. Meteors are fast. Very fast. And even though they may be bright their speed makes them more difficult to capture because their light does not linger over pixels in the sensor like stars or stationary objects do.

Since meteors may appear anywhere in the sky a common strategy is to use the widest possible lens you can and “fire the shotgun” at the sky. This strategy can work however use of a wider angle lens means the sensor area that will be struck by the light from a meteor is diminished.

Most important, however is the effective exposure. A short exposure with a wide open aperture at the highest acceptable ISO setting will catch the most meteors against a still sky. In other words ISO 2000, f/1.8, 20-30 seconds at 50mm focal length will capture a streak more effectively.  If you can stomach it, ISO 6400 will capture even more – and it may not matter that the image is noisy because you may end up using only the “streak” not the whole frame. It may seem tempting to just expose for say 10 minutes but unless the sky is very dark, that strategy will not work well.  Skyglow will overwhelm the area through which the meteor passes and thus reduce the contrast.

The second problem is where to point the camera.  If you use a wide angle lens or a fisheye lens you can point it almost anywhere you like. But it is helpful to know where the radiant point is. I like to be sure that the radiant point is in the picture. There is a downside to shooting near the radiant point: the closer the meteor is to the radiant point, the more “straight on” the meteor will be and the shorter the trail will be.  However pointing the camera somewhere away from the radiant point means your chances of catching a meteor go down exponentially – but what you do capture may have a longer streak.

It took me nearly 1200 attempts to get this one meteor in my back yard in San Jose, California. The camera was a Canon 50D at f/5.6 and ISO 1600. It is much noticeably grainier than a more recent capture on my 5D Mk II from Maui.

Below the Belt [5_020853]

Photo 2: One in 1600 shots that caught (almost all) of a meteor glancing through Orion’s belt. Settings: f/5.6, ISO 1600, 30 seconds, 23mm.

Half of a Brilliant Perseid [C_006711]

Canon 5D Mk II at ISO 2000, f/2.8

Here is an interesting thing to note: the radiant point of the Perseid Meteor is not far from the north celestial pole – that is, where Polaris the north star is. The radiant point of Leo, however is near the celestial equator. Why would that matter? It matters because in 3 hours the Leonid radiant point will have moved a fourth of the way across the sky while the Perseid radiant point will be probably still be in your frame.  In fact, David Kingham has written an excellent article about how to point your camera specifically for the Perseid Meteor Shower.

Back to Gary’s work for a moment. The meteors did not all come at once… no sir. The earth was busy rotating and the meteors shown in the photo were captured over 3 hours time! Had they all occurred at once they might have looked like the Photo 1 above.  Placing each meteor where it fell in the frame shows a different story – still compelling, but a bit more chaotic.

My thanks to Gary Randall for allowing me to show his excellent work. I heartily suggest you purchase a poster of his work to inspire you. I am doing so!

For more information about meteor showers and how to view them, there are many sites on the internet.  EarthSky.org is a great resource, for example.