Deep Near-Infrared Survey of the southern sky

Observing strategy

This page is aimed at describing the observation strategy for surveying the southern hemisphere with DENIS. It describes the notions of images, strips, and slots needed to understand the contents of the data releases.

Slots, Strips and Images

DENIS is a survey of the southern hemisphere.

The southern sky has been divided into 5112 regions named slots. A slot is 12 arcminutes in Right Ascension, and spans 30° in Declination. Two adjacent slots have two arcminutes overlap in Right Ascension or Declination. These slots are numbered so that each slot corresponds uniquely to a region of the southern sky.

Slots are distriutes in 3 declination zones. These zones overlap to ensure a complete coverage.
DENIS sky coverage

slot description
DENIS images are 12'x12' wide. Images are taken in Gunn-i, J and Ks simultaneously.

DENIS image

A DENIS strip is an observation of a slot. A single slot can be reobserved several times (for example if the photometric quality was not good during one night due to bad weather conditions). Thus, different strip numbers can refer back to the same slot.
A strip is made of 180 images, with 2 arcminutes overlap between two consecutive images, giving the full length of 30° in declination.

DENIS sky coverage in galactic coordinates

DENIS sky coverage in galactic coordinates