Is there a tutorial somewhere to this technique?
I can tell you how I did it, which is very similar to the technique in the link above:
1. There were 200 30-second frames taken. Set your intervalometer to take them with as little delay between shots as you can get away with.
2. Stack all the frames together in Photoshop in the order in which they were taken.
2. Next step is to look at each layer individually and clone out the airplane trails and any other extraneous garbage. Unfortunately, Arches has a lot of active flight patterns over it. Don't leave out any layers, no matter how bad they may be, because of cars or a bunch of planes. You can't break the star trail.
3. Change the blending method to Lighten on every layer. To save some time, do the next step on each layer at the same time:
4. Set the lowest layer to 1% opacity. To find the correct percentage jump to use each time, divide 100 by the number of layers you have. Thus, if you have 25 layers, each one will go up by 4%. If you have 100 layers, each layer's percentage will go up by 1% from the last. If you've worked your way up the stack from the bottom, you'll see no effect until you change the last layer, then the whole thing will snap into view.
5. You may need to take care of the landscape separately, but I didn't, because passing headlights lit up various places nicely throughout the stack.
6. Don't use any noise reduction, either in camera or later on. layering in Lighten mode will smooth out the noise.
By the way, take more pics than you think you'll use. That will give you some leeway when constructing it for the best visual effect. If there are a LOT of stars, you'll end up with a big blotchy mess if you use too many frames, so you may end up either darkening the whole thing or using fewer frames. I don't recall exactly how many I ended up with.