Question on ballistic app data inputs

[Klem]

The different types of chrono's work but all seem to have their peculiar disadvantages. Mine is an old fold-out optical Chrony with sky screens. It's cheap, and works, mostly (except on cloudy days, or late in the day, or when you don't open it out completely, or when you don't shoot exactly over the sensors, etc). I save my chronoing for night-time with lights. Fewer error readings and wasted loads.

If Santa is dishing out Lab Radars then he knows who's been 'naughty and nice'...I'm stuck with the Chrony.