This is a light pollution cut filter from Breakthrough Filters. For color tones when shooting starry skies and nightscapes. Official Name: "Breakthrough Filters" Purchased through personal import from the US official website (169 USD). ※ I am also listing various other filters, so please take a look. Below is translated information from the official website: ■Achieves stunningly clear depiction of starlight and true color fidelity. The Night Sky filter is housed in a weather-resistant, rugged X4 traction frame and features highly durable MRC16 coating and nanotec® coating for easy and quick cleaning. ■Designed for outdoor photographers. Artificial light pollution is located in the visible light spectrum, roughly in the range of 570-610 nanometers. Light pollution from artificial light can reduce the clarity of starlight by up to 50%. This orange color cast weakens the contrast between the stars and the space behind them, turning the background of space, which should be black, into an orange color. Removing light pollution is essential for taking beautiful photos of the night sky. However, finding a shooting location without light pollution is very difficult, and sometimes even impossible, depending on the location. Also, removing light pollution in post-processing is a destructive editing method that degrades image quality.