Astronomy Linux 19.04 is ready for downloads from page https://sourceforge.net/projects/astronomy-linux-19-04/

Add the repository

To use, add the following lines to your sources list file /etc/apt/sources.list :

for v. 16.04

deb http://vega.ap-i.net/astronomylinux xenial main

for v. 18.04

deb http://vega.ap-i.net/astronomylinux bionic main

Then import the apt key:

wget -qO - http://vega.ap-i.net/astronomylinux/key | sudo apt-key add -

Update your apt cache:

apt-get update

You can now update or install packages from this repository.