Some Schlieren shots – March 5, 2016
Since around November 2015, I’ve been very busy at work with some experiments involving the interaction of atmospheric plasma jets with the air or liquids. In order to study such interactions, I needed an imaging technique to visualize the gas flow of the plasma jet and its influence inside liquids (like water or alcohol). The best method for imaging such interactions is the Schlieren imaging technique. Being my first such optical setup (I did use some shadowgraphy setups in previous experiments, but not Schlieren setups), I did not want to increase the budget of the experiment too much, without first knowing the best method for creating such a setup.
What I did choose at the end of a two-week study, was the one-mirror Schlieren setup, which has a lot of advantages, both “economically” and due to its portability (in the laboratory we need most of the investigation setups to be mobile in order to use them on different experiments).
The main optical component of this one-mirror setup is of course…the mirror. Which interestingly enough, it can (and should) be a telescope mirror.
The final setup that I now use at work is indeed very good for our purposes, so good actually that I’ve decided to play a bit with a similar setup constructed at my home.
At work I use a 150mm F/4 (lambda/10) parabolic mirror, while at home I’ve selected the 200mm F/5 (lambda/8) mirror due to its versatile mirror cell.
For now, I have only three interesting results, showed as animations, of three different gas flows.
All of the imaging was done with the ASI 174MM camera and a 58mm F/2 old Helios objective. The exposure was kept at minimum (0.06 milliseconds, that is around 1/15000 of a second), and the frames per second rate was around 250 to 300. The animations are played at 20 fps, that is the slow-down factor is around 25 times. Sorry for the blinking background, but the light-bulb I’ve used is not good for such experiments (the flickering is due to the 50Hz frequency).
First animation shows the gas exiting a lighter:
The second animation, and the most impressive, shows the moment the flame from the lighter is formed and, afterwards, the changing shape of the hot gases:
And the final animation, showing the gas exiting a deodorant spray (won’t name the brand here):
Basically, any amateur astronomer interested in imaging the planets/Moon/Sun can create such an easy setup with the equipment at hand, that is the imaging camera, an old photography lens, a light bulb and of course the telescope mirror. Go ahead and try it, it will give you something to do when the skies are cloudy😉