ESO Archive Frequently Asked Questions

How is the DIMM seeing measured? Do you store the FWHM measured on the image itself?

The DIMM seeing is defined as the Full Width Half Maximum of a stellar image observed with a perfect large telescope, at 500nm wavelength and at zenith. It is measured over periods of a few minutes all night long. See the ESO Astroclimatology Overview web pages for more information.

ESO does not routinely extract and store a FWHM measured directly on image pixels.