Besselian element problem besselian element problem when modifying astronomy.js or astronomy.ts

[testori1972]

Is there any other way to calculate the width of the umbra other than the Besselian element which is inaccurate while Stellarium is accurate? We are trying the Besselian element from Stellarium-master on GitHub to test it until it can be accurate.

[cosinekitty]

The umbra in general will be an irregular curved shape on the Earth's oblate spheroid, with no single definite "width". A number can't be accurate or inaccurate, when there is no such number. So maybe you are asking something else, but it's not clear.