Persistence of Vision

I descided to make a new puzzle cache based around POV. The basic prinicple being that in the human eye an 'after image' persists for approximately one twenty-fifth of a second on the retina. The small device I outline here will display the final coordinates of a puzzle cache when it is swipped through the air at speed.
As usual the design is prototyped using an Arduino and then built from scratch using the raw components.

Basic POV with 7 LED array

An Atmega chip, 7 Leds and a 16Mhz crystal. I didnt bother with resisters to protect the Leds as at the 3.5V they should be fine, and I even excluded the recommended capacetors for the VIN and the crystal. Here is the minimal layout;

The device was powered by 3xAAA bateries, again, to keep the unit as small and simple as possible.
Here is a partial image from a swipe, displaying coordinates;

Lights in the sky