2. Setting up and tutorial datasets

2.1. Downloading the tutorial datasets

All the data needed to run this tutorial are found in the tutorial’s data package:

Download it and unpack it somewhere convenient.

cd <somewhere convenient>
tar xvf niriimg_tutorial_datapkg-v1.tar
bunzip2 niriimg_tutorial/playdata/*.bz2

The datasets are found in the subdirectory niriimg_tutorial/playdata, and we will work in the subdirectory named niriimg_tutorial/playground.


All the raw data can also be downloaded from the Gemini Observatory Archive. Using the tutorial data package is probably more convenient.

2.2. Datasets descriptions

2.2.1. Dataset for Example 1: Extended source with offset to sky

This is a NIRI imaging observation of an extended source, a galaxy showing as a dense field of stars. The observation sequence uses an offset to a nearby blank portion of the sky to monitor the sky levels since there are no area in the science observation that is not “contaminated” by the galaxy.

The calibrations we use for this example include:

  • Darks for the science and sky offset frames.
  • Flats, as a sequence of lamps-on and lamps-off exposures.
  • Short darks to use with the flats to create a bad pixel mask.
  • A set of standard star observations.

Here is the files breakdown. They are included in the tutorial data package. They can also be downloaded from the Gemini Observatory Archive (GOA).

N20160102S0270-274 (on-target)
N20160102S0275-279 (on-sky)
Science darks
N20160102S0423-432 (20 sec, like Science)
N20160102S0373-382 (lamps-on)
N20160102S0363-372 (lamps-off)
Short darks
Standard star

A note about finding the short darks in the GOA. Those darks are used solely to create a fresh bad pixel mask (BPM). In the archive, the calibration association will not find those darks, they need to be searched for explicitly. If you need to find short darks for your program, do as follow:

  • Set a date range around the dates of your science observations.
  • Set Instrument to NIRI.
  • Set Obs.Type to DARK.
  • Set the exposure time to 1 second.