22/01/2013

Teidestar camera sun shutter

For a long while now we've had two E2V L3Vision cameras which we use as nocturnal webcams. The cameras are extremely sensitive and can easily see stars and even see by star light. Over the last few years we started to see damage to the sensitivity of the chip following the line of the sun's progression through the sky. We eventually took the camera off line and sent it for repair by E2V. At this point we realised that we needed to do something to shield the camera from direct sunlight.

Our shutter design will have to meet the following requirements:
  • Reliable: It has to be able to operate reliably as there is nobody on site to maintain it.
  • Compact: It has to fit within existing camera housing around the current hardware.
  • Remotely controllable: The housing is mounted on the outside of the observatory. We have to be able to control the shutter from within the observatory.
These requirements lead us to the following design choices:
Ethernet control, so it can be operated by any machine in our observatory or remotely over the internet.
Rabbit RCM micro-controller, we have used these before in the system and they have proved themselves to be extremely reliable. The modules also have integrated Ethernet connectivity.

The sun shutter is one of those projects that has been on the back burner for a while. We work a little on it each trip, but it isn't top priority as the damage on the camera was caused over 10 years and we generally have more urgent work to deal with. Finally we have got to a point where the system is installed and working.

If you now look at the Teide stars camera in the day time you will see something similar to the image below. The dark patch in the middle is the shutter covering the lens, with light bouncing off the interior of the housing illuminating the edges.
 You will also see the shutter covering the lens at the start and end of the time lapse videos.

There isn't very much visible of the shutter system in the housing as it is all mounted in the gaps around other hardware. So instead of a picture of the system, here is a video of it in action.
video


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