Aleph is an asteroid’s virtual observatory designed for fast ephemeris production for ALeRCE (the LSST’s chilean data broker). Implemented in Python using the astronomical libraries “astropy” and “REBOUND” wich allows fast orbital integration. It can calculate ephemeris of particular asteroids or return all asteroids' positions in a given part of the sky at a given time for some observer (such as a known observatory or any position specified by the user, even space based telescopes). It has already been used to detect known asteroids in ZTF’s observations, with accuracies of 0.5 arcseconds better than other public services (like MPC’s web service or IMCCE's) and equivalent to ZTF’s astrometric accuracy. This is an easy-to-use Python package that enables astronomers to find known asteroids in astronomical images or to plan follow-up observations.We are currently building a tool to accurately predict occultations.