The 7DT array
Twenty 50-cm telescopes on direct-drive mounts, each with its own camera and filter wheel, operated as a single instrument.
What the array is made of
7DT is an array of twenty 50-cm commercial off-the-shelf telescopes. Each unit is a PlaneWave DeltaRho 500 optical tube assembly on an L-500 direct-drive mount in equatorial configuration, paired with a Moravian Instruments C3-61000 PRO CMOS camera. Units are identical except for the filters they carry. Sixteen of the twenty are deployed and operational as of June 2026; the remaining four complete the array. All operational units share a common configuration and show consistent optical performance in routine use.
| Optical tube | PlaneWave DeltaRho 500 — 508 mm corrected Cassegrain, f/3.0 |
|---|---|
| Mount | PlaneWave L-500 direct drive, equatorial, 20 deg s⁻¹ slew |
| Camera | Moravian C3-61000 PRO — SONY IMX455 CMOS, 9576 × 6388 px |
| Filter wheel | 9 slots per unit — Sloan broad bands and a share of 35 medium bands |
| Field of view | 1.34° × 0.90° at 0.5″ per pixel, 1.25 deg² per pointing |
Each subsystem is described in full under instrument. Measured on-sky performance is reported on the performance page.
Why an array rather than one telescope
Twenty commercial 50-cm units, each carrying a different share of the forty-filter medium-band set, cost a fraction of a purpose-built instrument, can be brought on line in stages, and can be reconfigured between science goals without hardware changes. Pointed together the units build a spectrum of one field; pointed apart they cover 25 square degrees at once.
Other multi-telescope arrays — GOTO, BlackGEM, LAST — take the same approach to off-the-shelf optics. What distinguishes 7DT is the filter set placed in front of them: 40 medium bands of about 25 nm width spanning 375 to 900 nm, distributed across the array so that the full set is covered in a small number of exposures.
System summary
| Array | |
|---|---|
| Telescopes in the array | 20 |
| Currently operational | 16 (as of June 2026) |
| Field of view per pointing | ≈ 1.25 deg² |
| Spectral resolution | R = 30–70 |
| Unit telescope | |
| OTA | PlaneWave DeltaRho 500 |
| Optical design | Corrected Cassegrain |
| Primary diameter | 50.8 cm |
| Focal length | 1537 mm |
| Focal ratio | f/3.0 |
| Image circle | 70 mm (≈ 2.6°) |
| Mount | PlaneWave L-500, direct drive |
| Mount slew rate | 20 deg s⁻¹ |
| Camera & filters | |
| Camera | Moravian C3-61000 PRO |
| Sensor | SONY IMX455 back-illuminated CMOS |
| Sensor size | 36 × 24 mm |
| Sensor dimension | 9576 × 6388 pixels |
| Pixel size | 3.76 µm |
| Pixel scale | 0.5 arcsec |
| Field of view per unit | 1.34° × 0.90° |
| Filter wheel | 9 slots per unit |
| Broad bands | Sloan u, g, r, i, z |
| Medium-band filters (design) | 40 |
| Medium-band filters installed | 35 (as of June 2026) |
| Wavelength coverage | 375–875 nm |
| Medium-band FWHM | 14–41 nm (typ. 25–30) |
| Site | |
| Observatory | El Sauce, Río Hurtado Valley, Chile |
| Coordinates | 30°28′16″ S, 70°45′47″ W |
| Altitude | 1600 m |
| Median seeing | ≈ 1.5 arcsec |
| Clear nights | > 300 per year |
| Zenith sky brightness | 21.97 mag arcsec⁻² |
| Computing & storage | |
| Processing server | Proton — 2 × AMD EPYC 7513 |
| CPU / memory | 128 cores @ 2.6 GHz / 512 GB |
| GPU | 2 × NVIDIA A100, 82 GB (NVLink) |
| Storage | Lyman 2 × 1.2 PB, Balmer 1.2 PB |
| Total capacity | ≈ 3.6 PB |
| Data link | KREONET, GridFTP ≈ 80 MB s⁻¹ |