Applying for Observing Time

Telescope time for ESO telescopes at the La Silla Paranal Observatory is allocated twice a year in periods of 6 months. Allocation periods run from 1 October through 31 March, and from 1 April through 30 September. Applications for observing time must be submitted using the Web-based p1 interface accessible at  

The Call for Proposals describes the conditions under which observing time is offered on the ESO telescopes on the La Silla, Paranal, and Chajnantor (APEX) sites of the Observatory. The document is available in electronic form via this Web page.

The deadline for Period 105 (1 April – 30 September 2020) is:

26 September, 2019

(12:00 noon, Central European Summer Time)

Applications for observing time for the ESO Telescopes have to be prepared using the p1 web system.
It is the PI's responsibility to resolve any submission problems well before the deadline. Please note that ESO cannot provide support beyond 11:00 CEST on the day of the deadline.


Call for Proposals for Period 105

Applications may be submitted for the usage of the telescopes, instruments and instrument modes specified in the Call for Proposals for Period 105.

  • Period 105 Call for Proposals

  • Useful links for Period 105
    Links to technical information about ESO facilities; foreseen changes in the performance of the offered instruments and useful information for the preparation of ESO proposals for the current call for proposals

  • Late Breaking News
    Please this page check regularly. It will contain information about the Call for Proposals that becomes available after the release.

Applications for observing time on ESO telescopes must be submitted by the respective deadline (end of March and end of September) using the Web-based p1 interface accessible at

This is accessible via your User Portal credentials. The Principal Investigator and all Co-Investigators must have an ESO User Portal Account. You can register at Please refer also to the instructions given in the Call for Proposals.

Please note that since Period 96 the seeing is defined as the seeing in the V band at zenith. See the Phase 2 Observing conditions page for more information.

In case you need practical assistance from ESO to prepare your proposal, please send an email to

The above address can be used for all questions and comments related to the proposal submission (how to prepare your proposal, what error messages really mean, etc.), as well as more general questions concerning instrument performance, Observatory policy, etc.