publicationJul. 2026
7DT Insight: Variability in Young Stellar Objects
Kim, M.-R. et al.
Center for the Gravitational-wave Universe · Seoul National University
7-Dimensional Sky Survey
A multi-telescope array, 7 Dimensional Telescope, built to find the optical counterparts of gravitational-wave events — and, in the process, to map the southern sky in forty colors.
01Right ascension02Declination03Distance04Radial velocity05Brightness06Wavelength07Time
Introduction
An array that observes in seven dimensions
The 7-Dimensional Telescope (7DT) is an array of twenty 50-cm telescopes at El Sauce Observatory in Chile, built and operated by the Center for the Gravitational-wave Universe at Seoul National University. Each unit carries a share of a forty-filter medium-band set, and together they turn imaging into low-resolution spectroscopy across 1.25 square degrees at a time. Sixteen units and thirty-five filters are in routine operation today; the remainder complete the designed array.
Science
One survey, seven fields
Every source in the field arrives with a low-resolution spectrum already attached. That single data product carries across most of the questions optical astronomy is asking: how galaxies assemble and stop forming stars, where the heavy elements are made, how fast the Universe is expanding, how black holes feed, what young stars do from one night to the next, and what the small bodies of our own solar system are made of. 7DS was designed for gravitational-wave counterparts; the same nightly images serve all of it.
20Telescopes in the array16 online
40Medium-band filters35 installed
30–70Spectral resolution R
1.25deg²Per pointing
7-Dimensional Sky Survey
Three tiers over the southern sky
The 7-Dimensional Sky Survey (7DS) runs on three tiers that trade area against depth and cadence: a single-visit reference map of the southern sky, a wide time-domain survey on a 10-14 day cadence, and nightly monitoring of a deep field at the south ecliptic pole. All three observe the same tile grid, so their data coadd without compromise.
RIS
Reference Imaging Survey
- Area
- 23,000 deg²
- Cadence
- Single visit
- Depth
- 19.1 mag
WTS
Wide-area Time-domain Survey
- Area
- 800–1,200 deg²
- Cadence
- 10–14 days
- Depth
- 22.2 mag*
IMS
Intensive Monitoring Survey
- Area
- 8.5 deg²
- Cadence
- 1 day
- Depth
- 23.6 mag*
*WTS and IMS depths are cumulative over the planned five-year operation, not the depth of a single visit. RIS depth is that of one visit.
The facility
Twenty telescopes, one system
Twenty DeltaRho 500 units on direct-drive mounts, sixteen of them observing tonight, one control computer per operational telescope, a robotic scheduler that can interrupt the night and start a follow-up exposure in under a minute, and a pipeline that reduces a 3,000-image night within the daily budget. 7DT is built to be pointed at a transient while it is still bright.
- Hardware
PlaneWave DeltaRho 500 × 20
A 508 mm corrected Cassegrain at f/3.0 on an L-500 direct-drive mount, with a Moravian C3-61000 PRO CMOS camera and a nine-slot filter wheel — 1.34° × 0.90° at 0.5″ per pixel, 1.25 deg² per unit.
- Site
El Sauce Observatory, Chile
1.5″ median seeing, over 300 clear nights a year, next to Rubin and Gemini-South.
- Operation
Robotic, unattended
RTCSpy runs the night end to end and interrupts it for an alert in under a minute.
- Pipeline
Same-night reduction
Py7DT clears a 3,000-image night in about five hours on 128 cores and two A100s.
Latest
News & publications
publicationJun. 2026
The 7-Dimensional Telescope and the 7-Dimensional Sky Survey: Status Report on Final Commissioning and Survey Operation
Kim, J. H. et al.
publicationJun. 2026
Py7DT: Data Reduction Pipeline of the 7-Dimensional Telescope
Hyun, D. et al.