This is the test tube photometer we describe in our recent paper: https://link.springer.com/article/10.1007%2Fs00284-017-1370-3 To make it real open source hardware we put together a shopping list and building instructions which you can find on openplant.science: Building instructions: http://openplant.science/2017/12/21/photometer-build-instructions.html Shopping list: http://openplant.science/2017/12/09/photometer-shopping-list.html