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 gmosls_tutorial_datapkg-v1.tar
bunzip2 gmosls_tutorial/playdata/*.bz2

The datasets are found in the subdirectory gmosls_tutorial/playdata, and we will work in the subdirectory named gmosls_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: Dithered Point Source Longslit

This is a GMOS longslit observation. The primary target is a DB white dwarf candidate. We will use this observation to show how a basic longslit sequence is reduced with DRAGONS. The sequence dithers along the dispersion axis and along the slit. DRAGONS will adjust for the difference in central wavelength and spatial positions, and then stack the aligned spectra automatically.

The data uses the B600 grating on GMOS South. The central wavelengths are 515 nm and 530 nm. We are using a subset of the original sequence to keep the data volume low. The effective sequence is:

(Science - Flat - Science - Arc) - (Science - Flat - Science - Arc)

with the first group of four at 515 and the second at 530 nm. The spectrophotometry standard was obtained about a month before the science observation.

The calibrations we for this example are:

  • Biases. The science and the standard observations are often taken with different Region-of-Interest (ROI) as the standard uses only the central area. Therefore we need two sets of biases, one for the science’s “Full Frame” ROI, and one for the standard’s “Central Spectrum” ROI.

  • Spectroscopic flats taken with each of the science and standard observations.

  • Arcs, for both the science and the standard observations.

  • A spectrophotometric standard.

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


S20171022S0087,89 (515 nm)
S20171022S0095,97 (530 nm)

Science biases


Science flats

S20171022S0088 (515 nm)
S20171022S0096 (530 nm)

Science arcs

S20171022S0092 (515 nm)
S20171022S0099 (530 nm)

Standard (LTT2415)

S20170826S0160 (515 nm)

Standard biases


Standard flats

S20170826S0161 (515 nm)

Standard arc

S20170826S0162 (515 nm)