Apple's new iPhone 6s and iPhone 6s Plus seem to be affected by a potential software bug present in iOS 9.0 and iOS 9.0.1 that appears to affect some, but not all apps which rely on data collected from the handset's compass and gyroscope sensors.
As first reported by AppleInsider, developer Fifth Star Labs has confirmed that reported issues with the Compass feature in its Sky Guide stargazing app are indeed limited to the new iPhone 6s and iPhone 6s Plus and do not extend to older hardware.