The best alternatives to BlackSight are Manual Camera for iPhone, NeuralCam, and Nizo. If these 3 options don't work for you, we've listed a few more alternatives below.
NeuralCam NightMode is the best night mode camera app featured on 9to5mac / VentureBeat / TheNextWeb / BGR / PetaPixel / DPReview / SlashGear / LAUNCH Ticker. 9to5Mac says “NeuralCam is not just the best iPhone camera app for night shots, but it is head-and-shoulders above the other apps.”