Questions
Short answers, each pointing to the page that carries the detail.
Observing
What does 7DT do that a conventional survey telescope does not?
It images through 35 medium-band filters rather than a handful of broad ones, so every exposure yields a low-resolution spectrum — R = 30–70 — for every source in a 1.25 deg² field. Classification that would otherwise need follow-up spectroscopy can be done from the imaging itself.
How quickly can the array respond to an alert?
Under a minute from alert ingestion to the start of a follow-up exposure. The scheduler interrupts the observing plan, repoints, and returns to the queue afterwards. See how to propose.
Can I request observations?
There is no general call for proposals yet; time is allocated within the collaboration and its partner institutions. Enquiries about observations outside the survey program are handled directly by the project.
What depth should I expect?
A single 100 s exposure reaches 19.06 mag at m400 and 19.61 mag at m475, where throughput peaks; Sloan g reaches 20.59 mag. Cumulative depths for each survey survey and the conditions these assume are on the performance page.
Data
How do I check whether my field has been observed?
Use the search on data access. Entering a position reports whether a tile there has data, how many nights and frames it carries, which medium bands were taken and the date range they span.
Is there a public archive?
Not yet. A public release is being prepared alongside the completion of the Reference Imaging Survey, whose first full cycle is anticipated by the end of 2027. Until then requests are handled by the project — see data access.
How soon after an observation are data available?
Normally the following day. Raw frames transfer from Chile overnight and a typical night clears the pipeline in about five hours after transfer. Target-of-opportunity data skip compression and the wait for sunrise, reducing latency to tens of minutes.
Why are coadd pixel values in microjansky?
Coadds are flux-scaled to a zero point of 23.9 AB, which puts each pixel directly in µJy. It suits the pixel-based analysis medium-band data invite, but it differs from the counts most archives deliver — see using the data.
What is a tile?
A fixed pointing on the survey tiling, 1.34° × 0.90°, numbered T00000 to T28519 by increasing declination. All three surveys and most target-of-opportunity pointings use the same tiling, so data taken at different times coadd without resampling.
Are all 35 filters calibrated to the same standard?
No. The original twenty medium bands are the calibrated set in operational use. The fifteen installed in late 2025 are being used but their spectrophotometric calibration is still in preparation, and their central wavelengths are not on a regular grid.
Software and credit
Is there software for planning observations or handling tiles?
Yes — supy provides target visibility, tile lookup and matching against a localization region, and filter response simulation. See available software.
Can I reprocess raw data myself?
Yes. Py7DT can be run offline with custom configurations and resumed from any stage of the reduction. Images are passed as file paths with metadata in FITS headers and YAML files rather than wrapped in a bespoke data model, so products stay inspectable outside the pipeline.
How should I acknowledge 7DT in a publication?
Contact the principal investigator before publishing so that collaboration authorship and funding acknowledgments can be agreed. Current wording is on the funding page, and how to use the data sets out the terms.
Ask a question
Questions not covered above go to the principal investigator. If the answer would be useful to others it will be added to this page.
If your question is about a data request, data access sets out what to include; for an observation, see how to propose.