| date | title | id |
|---|---|---|
2020-09-02 10:19:14 -0700 |
What is a DIMM? |
2020-09-02t17-19-14z |
A DIMM (Differential Image Motion Monitor) is an instrument for measuring Astronomical Seeing without having to rely on very large and expensive telescopes.
The system is equipped with a intensified CCD mounted to a smaller telescope such as a 350-mm Cassegrain.
The aperture of the instrument is then modified so to only allow light to pass through 2 circular holes, hence forming two images.
In ideal conditions, i.e. no Optical Turbulence, the incoming wavefronts would arrive flat, hitting both circles at the same angle.
However in reality, the turbulence perturbs the wavefronts, causing the light to enter each circular aperture at slightly different angles, causing the resulting images to shift relative to one another.
The time-averaged motion of the images is found to be proportional of the astronomical seeing, which can thus be measured by the instrument. [@pedersen_seeing_1988]
The mathematics and theory behind this proportionality can be found in the work by [@sarazin_eso_1990]