To properly Hyper your astrophotography film. Be advised that when color film is hypered at high temperature it is highly possible that it's Dye base will go through a color shift. Thats why it's important to only use proven films for this process. Why Use Nitrogen Gas Have you ever seen somebody setting up to do some serious astrophotography. The reason for this is to control moisture.
Moisture cause the film to buckle or curl.
This causes out of focus areas on your negative. The best way to use the Nitrogen gas is just prior to an exposure run Nitrogen gas thru the camera body. This will purge the camera body of any moisture. When the humidity is low this is all that will be required On nights of high humidity it would be better to have a small flow rate established during the entire exposure. This eliminates moisture from entering the camera body.