Description of the modified FMI-77 camera used in Kiruna
The roof of the optical laboratory, the allsky camera is seen in the
lower left corner of the picture.
This camera was originally designed by
Finnish Meteorological Institute, FMI in 1977, and modified
several times by IRF. The image
data is recorded on 16 mm colour film (Kodak Ektachrome 7251).
Overview of the instrument
The sky is imaged onto a convex mirror, which is photographed by
the 16 mm film camera located above the mirror. This design
results in a loss of information in Zenith.
The film camera is controlled by electronics, which exposes the
camera at a selected interval, (typically once every minute)
synchronizes the exposures with UTC, (using GPS) and advances the
film, etc.
Typical exposure time is 4 seconds, but every eighth exposure
is four times longer, in order to reveal faint auroras
When the camera not is in use, or during heavy snowfall, a
cover automatically closes and protects the mirror.
An electrical heater keeps the mirror free of moist.
This picture shows the convex mirror viewed almost as the 16 mm
film camera sees it (the betalight and camera are at the center of
the mirror in a 'real' image). The supporting rod for the camera
is towards geomagnetic South. The betalights was intended for
intensity estimations.
Format of the time display:
The current format of the time display is:
- YYYY mm dd HH MM SS EE
- YYYY Year.
- mm Month 01-12 for January to December.
- dd Day of month 01-31.
- HH Hours 00-23
- MM Minutes 00-59
- SS Seconds 00-59
- EE Exposure time (seconds)
In earlier data the time is displayed as follows:
- xx YY ddd HH MM SS
- xx Ignore this
- YY Year (19YY).
- mm Month 01-12 for January to December.
- dd Day of month 01-31.
- HH Hours 00-23
- MM Minutes 00-59
- SS Seconds 00-59
In this picture the cover is half closed.
Urban Brändström
Last modified: Tue Feb 24 10:15:11 UTC 2004
