FEROS-II at the MPG/ESO-2.20m :: Changing the FCU FEROS lamps
There are two type of lamps in the FCU , the hollow cathod lamps (ThAr and ThArNe) and the halogen lamps.
The halogen lamps can be changed by the support astronomer whereas the TharNe have to be changed by the opticians as it requires special tools and fine tuning
to make the proper alignment.
The lamps have to changed when a variation of the flux or a variation in the applied tension (checked on a daily basis by the TiO) is
Changing the halogen lamps
Halogen 1 : used to illuminate mostly the blue part of the spectrum.
The lamp can be changed without tools. Spares are located inside the FCU. The old lamp and the box of the new lamp have to be thrown away to avoid confusion.
Please, take care not to touch the new bulb with the fingers; you can use the plastic envelope to manipulate it. The bulb has to be put firmly on the base.
As the image of the bulb at the entrance of the the fibers focal plane is highly non unifrom, a fine adjustment of the position of the bulb is required.
Halogen 1 alignment
In order to check the proprer illumination of both fibers, a set of Flat-Field images should be taken . The procedure is the following
Go in the FEROS room
Login on the WS ( called wfwacu ) as user feros (same password as on wferos)
Use the mouse left button to start the ICS control panel and the SCCD Control panel (Fiera Control Panel)
On the ICS control panel, select and setup :
On the SCCD Control panel
On the RDT display, select Attach Camera in the pull-down menu.
Select Fast read-out mode (LR 625 Kps).
Choose a 2.4 sec exposure with the option repeat forever.
Start the exposure loop
Cuts on the RTD display will be used to check that the amount of ADU is sufficient and also that the relative fiber illumination is of similar intensity.
The halogen 1 should be move slighlty on its base (with a pen for example) to find the best position.
Halogen lamp2 can switched off if necessary.
Once the alignment is OK, stop the exposure loop and quit the SCCD panel . Quit the ICS panel and logout. Switch off the wfwacu screen.
Halogen 2 alignment
Once the new halogen 2 lamp is installed, the same procedure as for halogen 1 is used.
However, the optimum position should be find by slightly moving the 45 deg semi-transparent mirror which is used to combine both lamps.
The relative illumination of both lamps should be of similar intensity.