It uses the astronomy-bundle package by Andreas Möller. Since it is written in Typescript with ES6 syntax, the use of an ECMA-module loader like ESM is required (or a transpiler like babel).
This nodeJS app is running on free dynos on Heroku at https://astro6.herokuapp.com. It doesn't require credentials.
To run your own instalment of the app, type in terminal:
npm start
OR
node -r esm app-axios.js
Your HTML interface is running on port 3000
When the app is running, POST requests can be sent to the API as in the fetch() example included here.