These are the NightCap Pro results on an iPhone 5S: left is the standard iPhone camera app, in the middle the NightCap standard app, and on the right is NightCap Pro. 

While the latest generation of smartphones can in many ways rival traditional compact cameras, the lack of true long exposure functionality on most phones is a limitation and means taking images in very low light or capturing light and star trails is simply not possible.

However, now there's an app for that. NightCap was one of the first apps to enable long exposure capture on the iPhone and now its maker Interealtime has launched NightCap Pro, an enhanced version that adds iPad support, low-light video recording, a "light booster" and two ultra-long exposure modes to the standard app's feature set.

The Light Trail mode helps you capture star movement with unlimited exposure time. This mode also has a variety of settings that let you capture brighter images of night scenes while keeping image noise at bay and preserving detail. In Night mode, shutter speed can be set between 1/3 and 1 sec, depending on your device. The standard iPhone camera from Apple only offers 1/15 sec as the slowest shutter speed. In Video mode, brighter footage is achieved through reducing the frame rate. 

Full-resolution images can be saved in JPEG or TIFF format. NightCap Pro requires iOS 7 and is compatible with iPhone 4S or iPad 2 and later models. The app can be downloaded for $1.99 from the Apple App Store. The standard version is one dollar less.