Desiccant frame design for the Q453-HR or QHY8
This camera has a very large CCD chip, 23.4mm X 15.6mm. The TEC cooling takes the chip down to -35c below ambient. On cold and damp nights the glass window directly in front of the CCD chip will fog-up with dew/ ice crystals. It has been suggested to store the camera in a sealed bag or box with desiccant and cap it with a filter just prior to an imaging run. Others have suggested using a hair dryer to lightly blow-off the dew when it forms. I have tried both of these routines without much luck.
I like to leave the camera out in my observatory.
To help with this problem I have devised a way to surround the chip with silca gel.
Camera shown without nosepiece.........view of APS size CCD chip:
Dessicant Frame Design- FRONT VIEW
Dessicant Frame Design- SIDE VIEW
Note: Overall dimensions and depth of frame are totally dependent on nose piece design.
Finished-Assembled Frame (Material: Black Acetal "Delrin")
WITHOUT DESICCANT- View nosepiece with frame installed and UV/IR filter screwed on over the frame.
RESULTS- FILLED WITH SILCA GEL
So far, I have had excellent results.........serveral nights with 75% humidity and absoutely no fogging issues.
Also, I have been able to leave the camera setup on my observatory telescope.
To replace the silca gel, simply remove the UV/IR filter and add fresh desiccant.
With the semi-sealed nosepiece the dessicant should last for a reasonable period of time............yet, to be determined.