ORpilot wrote:
Infinity is not necessarily at the infinity mark. Temperature expands and contracts the glass and lens barrow. Polymer is less affected by temperature than metal. Mirror lenses are the most affected. If you have ever looked through a telescope, you discovered that infinity focus is very critical and changeable. Night shots are almost always shot wide open when there is the least DOF. You may wish to use masking tape to hold the focus in place because "shit happends".
Happy shooting