How to manipulate "login" publish?

Hey guys,
we need to manipulate the standard publish function, when a user logs in and received his data. The problem is, that we need to publish our Astronomy object instead of the pure Meteor.users collection. Otherwise our RN application gets conflicting data (because we have some additional fields in our Astronomy object which aren’t available on the collection publish). Any idea how I could change it?

You can just subscribe/publish the Meteor.users collection in your own code and the mergebox will take care of it. I do that in my app, where I have a simple Tracker that is tied to Meteor.userId() (reactive) that calls my own subscription which publishes additional fields for the loggedin user.

you can view level up on youtube, they have a video on user accounts, is complete and says how to do this.