Camera Maintenance
The G3 CCD camera is a precision optical and mechanical instrument, so it
should be handled with care. Camera should be protected from moisture and
dust. Always cover the telescope adapter when the camera is removed from the
telescope or put the whole camera into protective plastic bag.
Desiccant exchange
The G3 and G4 camera cooling is designed to be resistant to humidity inside
the CCD chamber. When the temperature decreases, the copper cold finger
crosses freezing point earlier than the CCD chip itself, so the water vapor inside
the CCD chamber freezes on the cold finger surface first. Although this
mechanism works very reliably in majority of cases, it has some limitations,
especially when the humidity level inside the CCD chamber is high or the chip
is cooled to very low temperatures.
This is why a small cylindrical chamber, filled with silica-gel desiccant, is
placed inside the camera head. This cylindrical chamber is attached to the
insulated cooled CCD chamber itself.
Warning:
High level of moisture in the CCD chip chamber can cause camera malfunction
or even damage to the CCD chip. Even if the frost does not create on the
detector when the CCD is cooled below freezing point, the moisture can be still
present. It is necessary to keep the CCD chamber interior dry by the regular
exchange of the silica-gel. The frequency of necessary silica-gel exchanges
depends on the camera usage. If the camera is used regularly, it is necessary to
dry the CCD chamber every few months.
It is possible bake the wet silica-gel in the oven (not the microvawe one!) to dry
it again. Dry the silica-gel for one hour at 150 to 160 °C. Exceeding the 170 °C
can damage the silica-gel and its ability to absorb moisture will be limited.
The silica-gel used in G3 and G4 cameras changes its color according to
amount of water absorbed – it is bright orange when it is dry and turns to
transparent without any color hue when it becomes wet.
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