Beginners treat the two weeks around full moon as lost. Experienced imagers shoot straight through them — they just shoot different things. Moonlight is sunlight with a bounce: broadband, brightest near the moon, scattered across the whole sky in a gradient that worsens with humidity and haze. Its damage is target- and filter-dependent, which is exactly what makes it plannable.
Broadband work (galaxies, reflection nebulae, clusters) degrades early and badly: past ~40% illumination, even 90° of separation leaves gradients that eat faint structure. Narrowband emission-nebula work barely notices: a 3–7 nm Ha filter rejects the moonlit continuum so effectively that many imagers reserve Ha for bright-moon weeks on purpose.
The working rules
Rules of thumb that hold up: broadband wants the moon below ~30% or below the horizon, and 60°+ away in any case. Ha runs happily to 80–90% illumination at 40–60° separation; OIII (bluer, closer to where moonlight peaks) is the fussier line — keep it for darker windows or accept softer contrast. And remember the moon sets and rises like everything else: a 70% moon that sets at 1 a.m. leaves you a genuinely dark second half — plan the broadband block for after moonset, not for another night.
The monthly rhythm that falls out: new-moon week is precious — spend it on broadband, the faint stuff, OIII. The gibbous weeks are Ha weeks. Full-moon nights are for Ha on bright targets, gear maintenance, and processing backlog. Structured this way, a month has almost no wasted clear nights.
- Keep one broadband and one narrowband project active at all times; the moon becomes a scheduler, not an obstacle.
- Moon separation matters more than illumination for narrowband — 30° from a half moon is worse than 100° from a nearly-full one.