MUSE p2 Tutorial

IMPORTANT: General guidelines for the preparation of Phase 2 material with p2 can be found here

This tutorial provides guidelines on how to prepare a set of Observation Blocks (OBs) with MUSE, the Multi Unit Spectroscopic Explorer on UT4 (Yepun) of the VLT. The specifics of this tutorial pertain to the preparation of OBs for Period 102 onwards.To follow this tutorial you should have familiarity with p2 : the web-based tool for the preparation of Phase 2 materials.  Please refer to the main p2 webpage (and the items in the menu bar on the left of that page) for a general overview of p2 and generic instructions on the preparation of Observing Blocks (OB).  Screenshots for this tutorial were made using the demo mode of p2, but should not differ in any way from one's experience in preparing your own OBs under your run.

Quick overview of general MUSE observing concept

Observations at the VLT are performed in terms of Observing Block (OB), which represents the basic observational unit. As such, astronomers specify their programmes in terms of OBs, which contain all the necessary information to obtain a single observation. Observations with MUSE are therefore performed through dedicated OBs that contain both general and MUSE specific information. In what follows we concentrate on the main MUSE specific information required to construct an OB, while for a quick summary of the general ESO Phase 2 material (i.e. details of the OB that are not instrument dependent) we refer the reader to this page.


The following table lists, for each observing mode, the available acquisition and observing templates

Acquisition template Observing template













MUSE_wfm-ao_acq_movetopixelLGS MUSE_wfm-ao_obs_genericoffsetLGS
NFM MUSE_nfm-ao_acq_LGS MUSE_nfm-ao_obs_genericoffsetLGS

In your proposal you have already indicated the mode, and the time you need to fulfill your science goal. This was done by consulting the MUSE User Manual and the Exposure Time Calculator. Hence, at this point, when preparing your MUSE OB the most important decision you have to make regards the observing strategy:

  1. Number of on-source exposures 
  2. how monitoring the sky background
Related to the first point, we strongly advise to break the on-source total exposure time in multiple exposures, and to take them, at least at two different position angles separated by 90 degrees, with small offsets (> spaxel size) to improve flat-fielding of the slicer and channel patterns during the data reduction.
Related to the second point, the way you should monitor the sky background depends mostly on the charactristic of your target/science field. In fact, if your target is an extended object that fills almost entirely the MUSE FoV, or if the field you are observing is very dense and crowded then in addition to the on-source exposures you will have to perform one or more exposures off-target in a empty region. On the other hands, if your field is sparse then there is no need for off-target exposure(s) because you will get a good estimate of the sky background directly from your science field.
The following links provide an OB preparation tutorial for a variety of science cases requiring diffent observing strategy and instrument setup:


By logging into the p2 demo, under the programme ID 60.A-9253(R) you can access to the USD-Tutorials folder where we have stored a sample of OBs designed for different modes and observing strategy. The example OBs are not editable but can be exported if needed. Please refrain from creating new OBs in the USD-Tutorials folder.


Instrument selector