SGO-004 — NGC 7293 (Helix Nebula)

Tom Shankapotomous
Nov 1
2 min read

Category: Planetary Nebula

Constellation: Aquarius

Capture Date: 2025-10-09

Instrument: Seestar S50 (Smart Telescope)

Filter: LP (Light-Pollution)

Exposure: 174 × 10 s (≈ 29 min total)

Stack Method: External Stack (Siril)

Processing: GIMP 3.0 (Noise Reduction + Clarity Emphasis)

File: Stacked_174_NGC 7293_10.0s_LP_20251009.jpeg

Location: Shank Gym Observatory – Backyard Setup (Bortle 5)

Target Description

The Helix Nebula (NGC 7293), also known as the Eye of God, lies about 655 light-years away in the constellation Aquarius. It is a planetary nebula — the luminous remains of a Sun-like star that has shed its outer layers, leaving behind a hot white dwarf core surrounded by ionized gas.

The blue-green inner core is dominated by doubly ionized oxygen (O III), while the outer reddish ring reflects hydrogen (Hα) emission. With an apparent diameter of roughly 25 arcminutes, it’s one of the largest and closest planetary nebulae visible from Earth.

Capture & Processing Notes

174 × 10 s light frames captured using Seestar S50 with LP filter under suburban Bortle 5 skies.

FIT sequence exported from Seestar internal storage and processed externally.

Stacking: Performed in Siril (normalized sum). Calibration frames omitted.

Post-Processing: Conducted in GIMP 3.0 (32-bit) focusing on

Noise reduction and background uniformity

Gentle contrast lift in the O III core

Clarity adjustment to bring forward outer Hα halo without over-saturation

No AI-based denoising used; results achieved through manual layer balancing and subtle Gaussian blending.

The workflow achieved a balanced, realistic aesthetic — controlled star sharpness with visible inner texture, particularly within the nebula’s “iris.”

Scientific Context

Planetary nebulae like the Helix are stellar fossils — transitional artifacts marking the death of medium-mass stars. Over roughly ten thousand years, the expelled gases expand outward while the stellar core cools into a white dwarf.

Spectral mapping of NGC 7293 reveals multi-shell dynamics, with an older, faint hydrogen envelope extending far beyond the visible ring — evidence of earlier mass-loss episodes.

This observation complements SGO’s ongoing series on “Stellar Endings and Cosmic Renewal,” exploring how dying stars recycle material back into the interstellar medium, ultimately seeding future star systems.

Catalog & References

NGC 7293 / Caldwell 63

RA 22h 29m 38s Dec −20° 50′ 14″

Distance ≈ 655 ly

Apparent Magnitude 7.6

Apparent Size 25′ × 20′

Composition: H II, O III, He II

SGO Cross-Reference

SGO-165 — M27 (Dumbbell Nebula): Planetary nebula comparison (color calibration reference)

SGO-172 — M57 (Ring Nebula): Smaller-scale analog in Lyra; similar core brightness profile

SGO-171 — IC 5070 (Pelican Nebula): Nebular region used for emission-line color correction under LP conditions