Sculptor Galaxy (NGC 253), fully calibrated stack from an equatorial-mode Seestar S30 Pro

Images and files

Record details

Object

Sculptor Galaxy (NGC 253, Caldwell 65)

Object type

Spiral galaxy (barred, starburst), seen nearly edge-on

Right ascension (RA)

11.8942°

Declination (Dec)

-25.4261°

Reference frame (RADESYS)

ICRS (J2000), image centre from the Siril plate solve against Gaia DR3

Observation date (local)

2026-11-07

Start time

2026-11-07 00:15:20 (UTC+11:00)

End time

2026-11-07 00:59:30 (UTC+11:00)

Time scale (TIMESYS)

UTC

Time source

Network time

Telescope and instrument

ZWO Seestar S30 Pro (30 mm f/5.3 apochromat, built-in colour CMOS), equatorial (EQ) mode

Filter

IR-cut (broadband visible)

Exposure time

30 s

Number of combined frames

53

Observing method

ZWO Seestar S30 Pro smart telescope (30 mm aperture, 160 mm focal length, f/5.3; 2160x3840 colour sensor, 2.9 μm pixels), IR-cut (broadband) filter, gain 200, sensor 24–25 °C. The scope was set up in equatorial (EQ) mode and polar-aligned with the Seestar app; capture was then run from Rob's computer through the Seestar's ASCOM Alpaca interface (raw frames, not the app's live stack): goto, plate-solve centring, small random dithers every 5 frames and re-centring every 40 frames. Night of 6–7 Nov 2026: 66 frames of 30 s (00:15–00:59 AEDT). Calibration in Siril 1.4: master bias (40 frames, 0.1 ms, internal dark shutter), master dark (25 x 30 s, 21.9–22.3 °C, internal dark shutter, hot-pixel correction), master flat (30 flats through the IR-cut filter, 7 Nov dawn, cloth diffuser lit by a torch, bias-subtracted). Then debayered, registered (two-pass), the frames outside the best 90% by star sharpness (wFWHM) dropped (53 of 66 used), sigma-clipped (3/3) and stacked with wFWHM weighting. Plate-solved against the Gaia DR3 astrometric catalogue (3.665 arcsec/pixel, effective focal length 163.2 mm), RBF background gradient removal, and colour-corrected with Siril photometric colour calibration (PCC) using Gaia DR3 star colours (665 stars). Then a linked auto-stretch and a mild saturation boost, and green-noise removal (SCNR). No colour or detail painted in, no AI or star removal. North is up (within about 1°), east to the left. The main image is a crop with Rob's semi-transparent 'rme' signature; the full frame is attached without it.

Bias frames

40

Dark frames

25

Flat frames

30

Astrometric solution (plate solve)

Solved by contributor

Calibration level

Calibrated

Processing level

Stacked

Processing software

Siril 1.4.0-rc2 (calibration, stacking, plate solve, PCC with Gaia DR3); capture by Lens over the Seestar's ASCOM Alpaca interface

Description

The Sculptor Galaxy (NGC 253), one of the brightest galaxies in the sky and a nearby 'starburst' galaxy about 11 million light-years away, seen almost edge-on. Its disc is crossed by mottled dark dust lanes, where stars are forming at a high rate. From the Riverina it passed nearly overhead before midnight, which made it a good first target of the night.

Uncertainty remarks

About 26.5 minutes of 30 s frames, so the faint outer disc and halo are thin and noisy; a longer run would show more. The darks (about 22 °C) were 2–3 °C cooler than these lights (24–25 °C), at the edge of the usual ±3 °C match. Flats were taken next morning after the scope had powered off; the focuser was returned to the same position (1270) and the filter and arm geometry were unchanged, but a small dust shift cannot be ruled out. Bright stars show faint blue halos from the optics and filter. Colours are calibrated against Gaia DR3 star colours (PCC). Distance is a literature value (about 11 million light-years), not measured here. Site position deliberately generalised to the nearest whole degree (about 60 km) to protect a private home.

Data quality statement

[withheld: contains a location]

Source

66 raw Alpaca sub-frames Light_NGC 253_30s_IR_20261107-001520 ... -005900 (FITS, read-only, 2026-11-07 00:15–00:59 AEDT); 49 earlier frames out of focus and excluded (kept in raw/subs-defocused); calibration frames darks-library/2026-11-06-night, calib-library/flats/2026-11-07-dawn/IR, calib-library/bias/2026-11-07; Siril log siril-20261107-siril.log; colour reference Gaia DR3 (ESA/Gaia/DPAC) via Siril local catalogue

Original FITS header retained

Yes

Place

Not shown on public record pages

From the Astronomy image profile, version 1.3.0, as signed for this record version. Not shown publicly: place, coordinate and site fields, fields the profile marks sensitive (such as observing times), and the names of observers, collectors and other credited people. In the title, captions and written descriptions, coordinates, street addresses, email addresses and phone numbers are replaced with a marker; other text, including any names or times written in it, is shown as the contributor wrote it.

Cite this record

Rob Evans (2026). Sculptor Galaxy (NGC 253), fully calibrated stack from an equatorial-mode Seestar S30 Pro. Clio Online Museum. https://cliomuseum.org/records/record-a8f500ad-f415-4847-8a9a-fc12861c3f45

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https://cliomuseum.org/records/record-a8f500ad-f415-4847-8a9a-fc12861c3f45

Published recordVersion 1

Creators

• Rob Evans https://orcid.org/0009-0004-6391-4464 (opens in a new tab) (verified with ORCID)

Version and provenance

Version identifier

version-938a4ce8-d5d1-4763-b893-fb4d783e5105

Canonical commitment

sha3-384:414f01a26d9cef49c5bf7c727e9ae2ae3d65b79ee2fae61740de697ce11002c9493297291dcc4715b2fadb9d80fcceee

Accepted

2026-11-06

Evidence profile and standards

• FITS
• World Coordinate System (WCS)
• IVOA Provenance Data Model