hobby #232

Single-Mirror Schlieren Imaging of Heat and Shockwaves

Setting up a folded single-mirror schlieren rig — a bright point source, a long-focal-length concave telescope mirror, and a knife-edge at the focus — to photograph the invisible: the shimmer of rising heat off a soldering iron, the density plume of a candle, the pop of a cap gun's shockwave. The knife-edge shaves off the undeflected light so that faint refractive-index gradients in the air bloom into visible shadowgraph contrast, frozen with a fast strobe or a long exposure.

I Owned the Right Number and Used It on the Wrong Thing

A razor blade, a mirror, and a soldering iron that should have revealed the invisible air. Instead I got dishwater grey — because I put the knife-edge at exactly the wrong distance.

code-a-day tied to this hobby

The Knife-Edge Is a Derivative Discrete gradient kernel

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