"At the time, we did not have a digital camera with the functionality of taking continuous pictures so I put huge faith into our knots and fishing line and sent up my iPhone in video mode.  Since then we have acquired a GoPro sports camera that is capable of taking video or time-lapse pictures.  The GoPro has the added advantage of having a wide angle lens. Total cost for our first balloon launch was $165, with the rental of the helium tank and the purchase of a 6 ft diameter balloon being the dominant expenses.  The tank had enough helium for two launches."