My PST has a motorized tuner which you can see in the picture. It gives fantastic control over the detail I can capture and a demo video showing the effects of small changes in tuning is shown here: https://vimeo.com/47357610
This consists of 35 frames which were captured with only 1 second of tuner movement between them. I can also turn down the motor speed for more precise control.
I read that the tuner ring varies the wavelength of the light and you can use this to identify which parts of the Sun are moving towards or away from you by the doppler effect. Something to investigate further.
