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The solar experiment

The FIES solar-experiment box is situated outside next to the entrance of the FIES building. The box contains a fiber that is pointing at the sky, and an iodine cell (for staff see iodine cell safety information ) for accurate wavelength calibration. The purpose of the box is to look at the solar oscillations through observations of the blue sky. The fiber can be connected to the FIES spectrograph to obtain spectra of the blue sky.

The box has a handle at the top, with which one can pull out the iodine cell from the beam (fully up), or push it into the beam (fully down). The handle is very stiff, so you need to apply lots of force (eat some eggs for breakfast).

The iodine cell is heated, and the control box is placed on top of the calibration unit trolley in the front room. The controller unit can be swithed on/off and the heater control can be enabled/disabled with the 'ENABLE' button.

The optical fiber that is aimed at the sky is relayed to the calibration unit trolley in the front room, where it can be connected to a different fiber that comes from the spectrograph (FIES fiber #5). This latter fiber should be either connected to the solar box, or to the calibration unit itself for normal operation of FIES.

When to switch the fibers

For normal use of FIES the blue spectrograph fiber should always be connected to the calibration unit. To check that the fibers are connected correctly for normal FIES observations, try the following on the FIES sequencer:
  expose 5
If you see a ThAr spectrum coming in, then all is fine.

When the spectrograph is connected to the solar box, this means that with every spectrum taken with FIES+TELESCOPE (any of fibers 1,3,4) you get a free simultaneous sky spectrum as well (through fiber 5 and the solar box fiber). Note that for a typical night-time stellar spectrum, you don't want this sky spectrum. In this case the entrance window to the box needs to be blocked, or the fibers need to be switched (see below).

Switching the fibers

To switch the fiber setup, follow the following instructions:

Open the top white door of the calibration unit in the FIES front room. There is a small black-metal fiber connection 'unit' , with fibers connected to it. Depending on the setup required, unscrew the blue spectrograph fiber (next to the empty spot) and screw it onto the empty spot, such that the light from either the solar box or the calibration unit will be fed to the blue spectrograph fiber.

Calibration unit connected to FIES, for normal FIES operation:

Solar box connected to FIES:

Back to top Last modified: 22-Nov-2007