Vortex star trails are the most complex trails to capture. It also requires a special motorized system to drive the zoom ring of a lens smoothly without shaking the camera while the shutter is open. The slow and gradual zoom in or out during the exposure period helps create the tunnel or vortex effect in star trails.
The technique shown in this video eliminates the need to buy such apparatus which is helpful for those who are hobbyists and tight on budget. Using only a single shot of the stars, you can now create amazing vortex star trails and add an artistic touch of color to them. Another major benefit of this technique is that it will give you flexibility on location and you will not have to spend hours taking hundreds of shots at a single spot for creating star trails.
You can read my detailed article about Star Trails on Digital Photography School by clicking on the thumbnail below:
Feel free to post your questions regarding this video tutorial. Enjoy!