A lot of you have asked how I create star trails that look like comets, so I’m gonna write about it, and that’s very sweet of me. 😀
I will discuss how to do this in Photoshop because, well, this is how I do it, but also, to the best of my knowledge, automated stacking programs such as startrails.exe ain’t gonna let you do this. In case it matters, I’m using Photoshop CS4, but you should be able to do this in any version of PS that allows you to stack. Awright…..now we’re just three steps from star trails with comet tail bliss!!
This tutorial assumes that you know how to take and process photos into star trails already. If you don’t, visit here.
1. CREATE STACK: In Photoshop, you select File > Scripts > Load Files Into Stack, and then select the files you wish to stack and follow the prompts accordingly. This will result in a HUGE .PSD file, with 50, 80, 120 layers, however many you loaded. And if you’re like me, they’ll be TIFFs. 16-bit TIFFs. Yeah. Have patience knowing that your computer is working very hard to make you happy right now.
2. ADJUST LAYERS: In the MODE PANEL WINDOW (which is the window that controls the Layers, etc. at the bottom right), change each layer from “Normal” to “Lighten”.
Some people occasionally use one of the other ones (such as screen, color dodge, linear dodge, lighter color), but “Lighten” is the most common, so whaddaya say we stick with it, cool? Do this for each Layer. Yup. That’s a lot. You can probably find a Photoshop Action for this if you Google around. And for that matter, you can probably find it for much of this star trails or comet tail creating process. Or you could create it yourself. I have not yet. No, I don’t know why I haven’t.
3. ADJUST OPACITY: Have you gotten carpal tunnel syndrome changing all your layers to “Lighten”? Great. Now, you can exacerbate that further by changing all of your layers’ Opacity. Y’see, the opacity defaults to 100% for each layer, so right now, you should have “normal” star trails that look like curved lines. What I do by this point is I make a flattened TIFF file of this in case I decide later that I really do want to have “regular” star trails.
Okay, back to adjusting opacity. Right next to the pulldown menu on the MODE PANEL WINDOW where you just changed all your layers from “Normal” to “Lighten” is another smaller pulldown menu that says “Opacity”. It defaults to 100%. So what you’re going to do is start from the top, and one by one, change each layers’ opacity to…well, something less than 100%. You start at 100% and gradually reduce the opacity until the last layer has a really low opacity, like 2% or 5% or whatever you think looks great. As you go along, you’ll slowly see the star trails begin transforming into comet trails, although the last part will remain full and bright until you adjust the very last Layer. After that, you should see the results of all that clicking. You should see each trail looking like a comet tail.
ADDENDUM (Summer 2013):
Beginning this summer, I began using a Photoshop action called Star Circle Academy Advanced Stacker PLUS. My workflow is now the following: I treat each individual photo first, cloning out unwanted airplane trails. Then I use the Advanced Stacker PLUS to create comet-like star trails. If it’s not aesthetically how I want it to look, then I will create the comet-like trails “by hand” as described above.
~~~~~~~
BACKGROUND INFO ABOUT THIS NIGHT SKY PHOTO OF BIG BEND IN ZION NATIONAL PARK:
So hey, about this photo….here’s a little more about how it came to be! I’m one of these people who are fascinated by the creative process, so I get into this kinda thing!
For this photo, I had to move the camera a couple of times. The moon seemed to be turbo-charged, cruising across the canyon sky too quickly. I moved the camera further over to the right, also a great view, and felt satisfied. I had The Organ bracketed by the Great White Thrown on the left and Angels Landing on the right, and all seemed good.
I had seen another photo of this taken by a photographer, one of the Milky Way. He and his son had set up this elaborate array of strobe lights, constant incandescent lights, and dish reflectors – all in all, five lights, placed 500 to 700 feet away from the camera, with strobes set to trigger via radio command. It was quite a setup.
I therefore was extremely surprised when I shined my Dorcy flashlight on The Organ and found that I could actually illuminate it even though it was monstrously huge and fairly far away. And sure, while the Dorcy is a very strong flashlight, almost like holding a car headlight in your hand, it still seemed absurd that I could do this. So I took one photo relatively early on, illuminating The Organ, and then began taking the sequence of shots to stack into a star trails photo, eventually blending the two together in Photoshop.
Title: Big Bend Star Trails
Info: Nikon D7000, Tokina 11-16mm lens. This is a combination of 54 individual photos, with each one 30 seconds, f/2.8 ISO 125, all stacked together for a total of 27 minutes. The photo of the stacked photos was blended with another photo of the foreground, consisting of The Organ (center), Great White Throne (left) and Angels Landing (right), which was shot at 52 seconds f/2.8 ISO 250. The Organ was light painted with a Dorcy spotlight. Taken around 10 pm 22 March 2013.
Photographer: Ken Lee
Location: Zion National Park, Utah U.S.A.
Equipment: Nikon D7000, Tokina AT-X 116, Feisol tripod.
VISIT ME, VISIT ME!
You can see more of these photos here on my Ken Lee Photography Facebook Page (poke your head in, say hi, and “like” the page if you would, uh, like). We discuss long exposure, night sky, star trails, and coastal long exposure photography, as well as lots of other things, so I hope you can join us!
And you can go to the Ken Lee Photography website, which has more photos from Ken Lee. Thank you very much for visiting!
kenleephotography.wordpress.com 
well written … thanks ken
thanks! one note, you can select all layers > lighten at once rather than doing 200+ individually.
Graham, thanks! Please let us know how to do this in detail, as this would save quite a bit of time. I’m using Photoshop CS4 in case that matters. Thanks again!!!
Saw this after posting my other comment. I understand this is 4 years old, so hopefully you figured it out. But for anyone reading this, you just select the top layer, go to the bottom layer, HOLD SHIFT KEY, and select bottom layer. Then just change mode to Lighten
Yeah. I’ve updated the blog several times to address other things, but it’s really difficult to keep up with an article. Back then when I wrote that, this was indeed the case. You had to do each one independently. No longer, thankfully. Thanks, Joel, I do really appreciate the comment!