Helix Nebula (NGC 7293), 60-minute stack, dual-band filter, colour-calibrated, Seestar S30 Pro

Images and files

Record details

Object

NGC 7293 (Helix Nebula)

Object type

planetary nebula

Right ascension (RA)

337.473 (unit not recorded)

Declination (Dec)

-20.7373°

Reference frame (RADESYS)

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

Observation date (local)

2026-10-31

Time scale (TIMESYS)

UTC

Time source

Phone network

Telescope and instrument

ZWO Seestar S30 Pro (30 mm f/5.3 apochromat, 160 mm FL, built-in colour camera 3840x2160, 2.9 μm pixels)

Filter

LP dual-band (H-alpha / OIII), built in

Exposure time

60 s

Number of combined frames

60

Observing method

ZWO Seestar S30 Pro smart telescope (30 mm aperture, 160 mm focal length, f/5.3; 3840x2160 colour sensor, 2.9 μm pixels), equatorial mode, built-in LP dual-band (H-alpha/OIII) filter, gain 200, sensor 27–30 °C. 85 frames of 60 s captured from 22:11 to 00:32 AEDT. Version 2 (reprocessed 2–3 Nov 2026) in Siril 1.4: debayered and registered (two-pass; 67 frames registered), the best 60 kept by star sharpness (wFWHM), sigma-clipped (3/3) and stacked with wFWHM weighting (60 min total). The stack was then plate-solved against the Gaia DR3 astrometric catalogue (990 image stars; 3.660 arcsec/pixel, effective focal length 163.4 mm) and colour-corrected with Siril photometric colour calibration (PCC) using Gaia DR3 star colours (978 stars), with RBF background gradient removal before and after. Then a linked auto-stretch and a mild saturation boost. No colour or detail painted in, no AI or star removal. No darks or flats applied. The main image is a crop around the nebula with Rob's semi-transparent "rme" signature; the full frame is attached without it.

Bias frames

0

Dark frames

0

Flat frames

0

Astrometric solution (plate solve)

Solved by contributor

Calibration level

Partially calibrated

Processing level

Stacked

Processing software

Siril 1.4.0-rc2 (plate solve + PCC with Gaia DR3)

Description

The Helix Nebula (NGC 7293) in Aquarius, a planetary nebula: the glowing gas shell thrown off by a dying Sun-like star, about 650 light-years away. Red shows hydrogen-alpha in the outer ring and the blue-green core shows doubly ionised oxygen. One hour of 60-second frames, restacked from the raw sub-frames and colour-calibrated against Gaia star colours.

Uncertainty remarks

Colours are calibrated against Gaia DR3 star colours (PCC), but the dual-band filter passes mainly H-alpha and OIII light, so nebula colours are still not true visual colour. Spectrophotometric calibration (SPCC) was not used because it crashes in Siril 1.4.0-rc2. No dark or flat frames, so faint gradients and hot pixels may remain. The plate solve shows the north–south axis runs vertically to within about 1 degree; the image keeps the Seestar's display orientation. Distance (about 650 light-years) is the literature value, not measured here. Site position deliberately generalised to the nearest whole degree (about 60 km) to protect a private home.

Data quality statement

60 of 85 frames stacked after registration and star-sharpness filtering. Astrometry and colour from Gaia DR3 via local Siril catalogues (astrometric catalogue for the plate solve; PCC for colour). Version 1 had automatic colour balance only and was not plate-solved; version 2 replaces it with catalogue-based colour calibration and a plate-solved centre. GPS and camera metadata removed from the published images; the raw FITS (which hold the site position) are kept privately.

Source

Seestar S30 Pro sub-frames Light_NGC 7293_60.0s_LP_20261031-221300 to _20261101-003214 (85 FITS); Siril log siril-20261102-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 1.1.0, 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). Helix Nebula (NGC 7293), 60-minute stack, dual-band filter, colour-calibrated, Seestar S30 Pro. Clio Online Museum. https://cliomuseum.org/records/record-c2d81e5f-aad0-4e78-9667-2b064af5bfde

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https://cliomuseum.org/records/record-c2d81e5f-aad0-4e78-9667-2b064af5bfde

Published recordVersion 3

Creators

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

Version and provenance

Version identifier

version-20ab9f32-f50e-416b-b750-5e229cdda0d7

Canonical commitment

sha3-384:f1a2a88bda9d4c6ae4734009e3f1b100012bd09c7883099a2f594720234ceae2f900c1d6a6a3a2e43bf4e8fd69c4a5a4

Accepted

2026-11-03

Previous version

version-5d1cc2b9-e4dc-4daa-a489-45e05164f3b4

Evidence profile and standards

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