Orion Nebula (M42, M43) and the Running Man, HDR stack with a short-exposure core, colour-calibrated, Seestar S30 Pro

Images and files

Record details

Object

Orion Nebula (M42) with M43 and the Running Man Nebula (NGC 1977)

Object type

Emission and reflection nebula (star-forming region)

Right ascension (RA)

83.7237°

Declination (Dec)

-5.41°

Reference frame (RADESYS)

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

Observation date (local)

2026-11-05

Start time

2026-11-05 13:16:19 (UTC)

End time

2026-11-05 15:32:11 (UTC)

Time scale (TIMESYS)

UTC

Time source

Camera clock

Telescope and instrument

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

Filter

Light-pollution dual-band (H-alpha and OIII)

Exposure time

60 s

Number of combined frames

119

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), built-in light-pollution (dual-band) filter, gain 200, sensor about 21–23 °C, alt-az mount. Night of 5–6 Nov 2026: 35 frames of 60 s (00:16–01:41 AEDT) and 98 frames of 10 s (02:09–02:32 AEDT). Each sub was dark-subtracted on board by the Seestar with its own master dark. Each set was stacked separately in Siril 1.4: debayered, registered (two-pass), the frames outside the best 90% by star sharpness (wFWHM) dropped (31 of 35 and 88 of 98 kept), sigma-clipped (3/3) and stacked with wFWHM weighting. Each stack was plate-solved against the Gaia DR3 astrometric catalogue (3.665 arcsec/pixel, effective focal length 163.2 mm) and colour-corrected with Siril photometric colour calibration (PCC) using Gaia DR3 star colours (600 and 576 stars), with RBF background gradient removal. HDR blend: the 10 s stack was registered onto the 60 s stack, background-subtracted, scaled by the measured brightness ratio (6.0–6.3, expected 6) and blended in where the 60 s stack reaches 55–90% of its peak (about 3,500 pixels in the core). Then an asinh stretch, a linked auto-stretch and a mild saturation boost. No colour or detail painted in, no AI or star removal. The main image is a crop with Rob's semi-transparent 'rme' signature; the full frame is attached without it.

Bias frames

0

Dark frames

5

Flat frames

0

Astrometric solution (plate solve)

Solved by contributor

Calibration level

Partially calibrated

Processing level

Composite

Processing software

Siril 1.4.0-rc2 (stacking, plate solve, PCC with Gaia DR3); HDR blend in Python/NumPy (Lens)

Description

The Orion Nebula (M42) in the sword of Orion, with De Mairan's Nebula (M43) beside it and the bluish Running Man Nebula (NGC 1977) further along the sword: a cloud of glowing hydrogen about 1,350 light-years away where new stars are forming. From the southern hemisphere Orion appears 'upside down', and this image keeps that view: north is down. The core around the Trapezium stars is far brighter than the outer nebula, so two sets were combined: 60-second frames for the faint outer clouds and 10-second frames for the bright heart, which would otherwise burn out to white.

Uncertainty remarks

About 31 min of 60 s data and 15 min of 10 s data. Field rotation from the alt-az mount caused the Seestar to reject over half of the 60 s frames, so the faint outer nebula is thinner than a longer run would give. The core blend is a measured, linear combination, but where the two sets meet the transition is a smooth weight, not a measurement. Colours are calibrated against Gaia DR3 star colours (PCC) through a dual-band light-pollution filter, which passes mainly hydrogen-alpha and oxygen-III light, so colours are not true broadband colour. No flat frames, so faint gradients may remain. Distance is the literature value (Gaia-based, about 1,350 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

119 of 133 frames used after star-sharpness filtering (31 x 60 s + 88 x 10 s). Plate-solved and colour-calibrated against Gaia DR3 via local Siril catalogues. GPS and camera metadata removed from the published images; the raw FITS (which hold the site position) are kept privately.

Source

[withheld: contains a location]

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). Orion Nebula (M42, M43) and the Running Man, HDR stack with a short-exposure core, colour-calibrated, Seestar S30 Pro. Clio Online Museum. https://cliomuseum.org/records/record-dd892e18-4735-4362-ab59-4641232da963

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https://cliomuseum.org/records/record-dd892e18-4735-4362-ab59-4641232da963

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-5bf30dd1-2d50-468d-ba40-990e71812880

Canonical commitment

sha3-384:506b7fa337110193cd666b5396f7cda2cacc0c6d9d3bb392e8d5d406a714a1891b9b078b260084c1c6c975ccc5374e59

Accepted

2026-11-05

Evidence profile and standards

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