Notes about the HNS file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The HNS file type is primarily associated with 'Hallo Northern Sky (HNSKY)' by Han Kleijn. Hallo Northern Sky or HNSKY is a free planetarium program for windows with 26000 deep sky objects and all stars to magnitude 12 and with the original GSC CD's, GSC-ACT or the USNO UCAC2 to magnitude 16.