What is Tangra?
Tangra is a software for reducing astronomical video observations such as asteroid occultations, astrometric and photometric video observations of comets and asteroids. It opens the vast majority of the video files without the need of AviSynth as long as you have the codecs installed. It is intuitive to use and offers a number of different algorithms for photometric measurements including aperture photometry, PSF photometry and optimal extraction. Another useful feature is that Tangra allows you after the measurement is completed to see exactly how each apperture was placed around each object in each measured frame. Also the measured light curve can be saved into a file much smaller than the video and the file can be sent to other people for review and remeasure. This could be very helpful when there is doubt or uncertainly in the light curve.
Tangra is used by numerous occultations observers around the world for light curve reduction. More information about the photometric algorithms used in Tangra can be found in the Video Photometry atricle.
Both Step-by-Step LightCurve Reduction Examples and Step-by-Step Astrometry Reduction Examples are also available.
The majority of the functionality, excluding Astrometry, is free but without technical support. This includes the reduction of light curves of asteroidal occultations. To use astrometry or to receive technical support you need to purchase a license.
Tangra has been also used by at least two observatories to reduce and report to the MPC astrometric positions of a number of Near Earth asteroids and comets.
A third cross-platform version of Tangra has been announced. You can find out more about it on the Tangra 3 Web Site