From PyThea >=0.9.0 the json fitting files will be slightly different than the old ones.

[AthKouloumvakos]

This is a general discussion about the changes in the fitting files after PyThea >=0.9.0.

There is on-going work to improve the JSON fitting files and overall the accuracy of the fittings. Hence, until reaching V1.0.0 of PyThea there are going to be some notable changes in the structure of the JSON fitting files files that may not affect your work but come with some caveats. This discussion is to provide some further information on the changes and how to deal with them.

1. Due to a change in the fitting time input, the new fitting files may have slightly different times for the same images.

What changed: The new fitting time input is based on the sunpy.map.Map.date_average instead of the sunpy.map.Map.date. The first one is the average time between the start and end of the image capture whereas the second is usually the start time without taking into account the total exposure time.

Why it is important: For the heliospheric imagers using the map.date which is at the start of the exposure can be problematic for the accuracy of the fittings and the final kinematics. The exposure time can be many minutes and the structures observed may have displaced significantly from the beginning of the exposure to the end. It is obvious that for EUV imagers and coronagraphs, this is not an issue because the exposure is typically a few seconds or minutes, respectively.

Should you worry?: Not at all, your past fitting files are just fine. The only change you may notice is the time stored in the json files for each fitting. The kinematics is not affected for fittings performed with EUV imagers and coronagraphs but may slightly change for fittings with heliospheric imagers. If you have used STEREO HI imagers you can remove that points and re-fit. Then you may compare your old kinematics to the new ones. The new kinematics will definitely be more accurate now.

Loading fitting files: Loading past fitting files needs some attention. If you have used STEREO HI imagers it is strongly recommended to remove these points and re-do the fitting for these few frames. In any other case, there is no need to change anything, the time differences are very small and do not affect the kinematics. Note, however, that if you want to change a fitting you have to remove the point closest to the image that you fitted because the timestamp will be slightly different and the app will not update the values automatically.