#Blackholes: #Event #Horizont #Telescope and the #ehtim #free soft #program

.. the image software used by the Event Horizon telescope, which have been record the first image of a black hole, is free software and not a business privative program, https://u.fsf.org/2sm The program uses the Method of Maximum Entropy, (MEM), which finds the most consistent image using data collection that maximizes an entropy function, analogous to the record of a prior probability distribution ...

Recently the NASA, using the powerful Event Horizon Telescope (EHT, in conjunction with other telescopes) has been able to photograph using a kind of "High-Resolution Linear Polarimetric Imaging" program, especially made it for the Event Horizon Telescope, Chael et al. 2016 (https://arxiv.org/abs/1605.06156).

 

These techniques have been possible to apply together with a free software program "ethim" or "eht-imaging"; in the scientific document (due the link is more to explain the techniques of manual analysis rather than program itself) is explicitly cited ( chapter 5 about the program):
 

Our imaging code is written in Python and uses the L-BFGS minimization routine in the Scipy package. Our imaging
programs as well as a variety of routines for simulating and manipulating VLBI data are available at https://github.
com/achael/eht-imaging.

The program uses the Maximum Entropy Method, (MEM), which finds the most consistent image using data collection that maximizes an entropy function, analogous to the recording of a previous probability distribution ... MEM image algorithms have been in use for decades but not previously in systems and programs due to the low power and limitations of hardware AND FOR PROBLEMS OF LICENSE AND COSTS REGARDING IMPLEMENTATIONS that now with free software are possible and cheat.

Linear polarization images of the synchrotron radiation around the Active Galactic Nuclei (AGN) identify their projected magnetic field lines and provide key data to understand the accretion physics and output of supermassive black holes. The polarimetric MEM algorithm combines a Stokes I imager that uses only bispectral measurements that are immune to atmospheric phase corruption with a set of Stokes Q and U images operating in robust polarimetric relationships.

This means that thanks to free software, equations are applied that allow to filter the "garbage in the photo" produced by the earth's atmosphere, and thus discover the true image .. this reuniting several data together from different places (there were several telescopes together and the data is processed in the Event Horizon).

The FREE "ethim" program allows data collection and processing, much better than other proprietary solutions due cheat and possibility of modification that fit to the requirements of the implementations.