This page provides a summary of safety procedures astronomers and staff members must follow when operating the DAO telescopes. If you have not previously received training in any of the procedures outlined below you must request it from a member of the DAO telescope support staff. Since HIA staff are responsible for the safety of the telescope users your failure to follow any of these safety procedures may result in the loss of your observing privileges. Any accidents involving personnel or equipment should be reported immediately to Telescope or HIA Site Staff.
1.8-m observers are instructed NOT to use the passenger elevator in the 1.8-m dome if they are alone in the dome. The elevator has, on occasion, tripped a power breaker and this can obviously lead to the user being trapped in the elevator.
While normally not something an observer has to do, if the elevator is being used to transport an LN2 transfer dewar to the ground floor the dewar is NOT to be accompanied by a human! Place the dewar in the elevator, close the door and use the lift buttons to move the elevator up or down as required with the dewar as the only "passenger" in the elevator.
Ensure that the 1.8-m telescope is parked and stopped. Executing the “Park” command in DICE or on the TCS computer should do this. NEVER fill the CCD dewar when the telescope is tracking and/or not parked at the zenith.
Put on the protective rubber gloves, apron, and mask normally located on the portable hand cart located near the entrance to the 1.8-m telescope observer's room.
Move the LN2 transfer dewar into position in front and slightly to the side of the CCD. There are normally two such dewars near the telescope; use the one that has a fill tube attached to it.
Remove the small, white, plastic plug at the entrance to the CCD dewar.
Use the special tool provided to remove the inner metal plug of the CCD dewar by turning the plug counter-clockwise until it is free and can be pulled out of the dewar. Note: the dewar can be filled with this inner plug in place but in that case it will take much longer.
Insert the transfer dewar's fill hose into the CCD dewar's fill opening. Ensure that the hose is inserted all the way in by gently probing for the inner opening to the dewar with the fill tube. Do not apply any excessive force with the fill tube. Once the hose is in place it is also best to locate the transfer dewar so that its yellow and black valves are not immediately below the CCD dewar's fill opening from where LN2 will spill when the dewar is full.
Check the transfer dewar's pressure. It should be at least 9 psi. It not, the transfer dewar needs to be pressurized first before attempting to fill the CCD dewar or the fill time will be very long. Normally the transfer dewar only needs to be pressurized soon after it was filled.
To pressurize the transfer dewar (if the pressure is less than 9 psi):
Locate the red curly hose which is attached to the dry nitrogen line.
Connect this hose to the intake port on the transfer dewar. Pull out the sleeve on the coupling, push the coupling in, and release the sleeve.
Open the black valve of the transfer dewar. The pressure should start rising. If not, check the pressure in the main tank downstairs.
Open the yellow valve on the transfer dewar to begin the flow of LN2 from the transfer dewar to the CCD dewar. The fill tube may slide out of the dewar a few centimeters when filling starts; if so, reposition the fill tube.
Continue filling until you see LN2 flowing out of the CCD dewar fill opening. This usually takes only a few minutes when the inner plug of the CCD dewar has been removed.
Close the yellow valve once LN2 is spilling out of the CCD dewar fill opening.
If the CCD was at or near room temperature when filling started we recommend that you now let the CCD cool to about -100C (the temperature is displayed in the DICE Exposure GUI) and then open the yellow valve briefly again to top up the dewar once more after the original rapid LN2 burnoff.
Close the black valve and disconnect the red curly dry nitrogen hose if it was connected.
To make it easier to extract the fill tube from the CCD without damage, wait a few minutes until the rubber portion of the fill tube has thawed somewhat so that it is no longer hard. Then slowly roll the transfer dewar away from the telescope and the CCD.
Return the transfer dewar to its storage location well away from the telescope, spectrograph and pier.
Use the special tool to insert the CCD dewar's inner metal plug. You may have to feel for the inner opening before the plug seats itself properly inside the dewar. Then turn the tool a few turns clockwise until snug. Do NOT over tighten!
Insert the CCD dewar's white, plastic plug.
Remove the protective gear and return it to its proper storage location.
Make sure all other hardware (rolling stairways, etc.) have been moved away from the telescopes.
DAO telescope users are requested to acknowledge the use of the DAO facilities in their publications.
*Guest investigator, Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics,
National Research Council of Canada.