Acquisition
Field 468 · RA150 Dec2
ONE PHOTOGRAPH IS NEVER ENOUGH.
Everything downstream in this pipeline exists to compare one image against others of the same patch of sky — that premise comes first because nothing else works without it. This tutorial covers why the array surveys at all, and the real instrument and cadence behind it. Nine tutorials, read in order — this is the first.
Unlike the Overview page, nothing on this page is invented. This describes the real pipeline — the same one the viewer, survey and cell browsers actually run.
A single exposure only shows the sky as it is, never as it changes.
Everything downstream in this pipeline exists to compare one image against others of the same patch of sky — that premise comes first because nothing else works without it.
One frozen frame is a photograph, not a measurement. Something new, brightening, fading, or moving only shows itself when you hold one exposure of the same patch of sky against others taken at other times.
The instrument and the repetition
The imaging comes from the Zwicky Transient Facility, run on the 48-inch Samuel Oschin Schmidt Telescope at Palomar Observatory. The archive is public, served through IRSA/NASA-IPAC — no proprietary access required. ZTF revisits a given field roughly twice a night, and that raw repetition is what the whole pipeline is built on.
The primary field studied is field 468, centered near RA 150°, Dec 2° — a patch that happens to sit inside the COSMOS survey footprint, one of the most thoroughly catalogued regions of sky, which makes it a useful place to check results against known objects later.
One field, not a ceiling. Field 468 is the worked example, not a limit of the method. The same code has since been generalized into a survey harvester that sweeps many fields and many nights, storing results in a SQLite results store and exporting them to the static-JSON survey browser covered in tutorial 07.
Go watch it run.
Everything above is the real pipeline, explained in the order it runs. The browsers below are that same pipeline's actual output — a working ZTF difference-imaging system, not a mockup of one.
Or read what this project actually is