Most of the scientific instruments used in astronomy must be cooled either through cryogenic equipment or through filling them with liquid nitrogen. This is what the instrument fills used to look like: fill a small Dewar with liquid nitrogen from a large Dewar, then pour it in to the instrument. The funnel, in this case, is a cut-apart fruit bottle. Now a different model of pressurized Dewar is available and a hose is inserted in to the instrument and filled not unlike filling a car's tank with gasoline.
This is, again, the retired instrument Grimm.