Place. Every altitude, rise and set, twilight, moon-interference, and eyepiece pick uses one site: the Census Bureau 2024 ZCTA internal point for 98374, 47.129077°N, 122.263923°W. Times and calendar dates are Pacific (America/Los_Angeles), including meteor peaks at 1:00 AM local and eclipse dates through the end of that local day. The clock shows that zone even if the browser is set somewhere else.

Method. Sun, Moon & planet positions use standard low-precision orbital elements (Meeus/Schlyter), accurate to a few arcminutes (a tenth of the Moon's width) — plenty for "is it up and roughly where," not precision Goto pointing. Planet magnitudes are computed per-apparition from real photometric fits (Mallama & Hilton 2018), not fixed values — Saturn's is globe-only (no ring-tilt boost, which can add several tenths of a magnitude when the rings are wide open; the ring cue is a separate opening-angle estimate). Uranus and Neptune omit a small pole-orientation term worth a few hundredths. Galilean moons are a low-precision which-side sketch, not a transit timetable. Deep-sky catalog is the full 110-object Messier list (via OpenNGC) plus a short list of bright NGC, Caldwell, and double-star showpieces, J2000 coordinates — 8 far-southern Messier objects (M6, M7, M54, M55, M62, M69, M70, M83) and anything that never clears 15° from this latitude are left out. Doubles use stored separations and position angles, and an eyepiece from that separation plus the seeing ceiling. Sky darkness for 98374 is an estimate (suburban Seattle–Tacoma metro, roughly Bortle 6–7) — check the live map for your exact yard. The observing score adds darkness length, moonlight through the dark window, and how many bright planets and good-contrast deep-sky targets are up, then scales that by Open-Meteo cloud cover only when the forecast actually loads. Seeing and transparency can shave a few more points, and only when those fields are actually in the forecast. The week strip repeats that score for the next seven nights. The dusk-to-dawn curve samples the same sky factors and multiplies each point by that hour's cloud cover. The faint line is that sample with clouds left out. A separate usable block also folds hourly precip, wind, dew spread, and visibility into start and stop times. Twilight bands on that curve are the Sun at −6°, −12°, and −18°. If the Sun never reaches −18°, sunset to sunrise is labeled twilight, not astronomical dark. The session tour is still the 60–90 minutes around the score peak — shorter only when the night itself is — ordered west first, with each eyepiece taken at the middle of the block. A comet is shown only from a dated catalog position and magnitude. An empty visitors card means nothing on that list is active.

Visibility. The "should be visible" call on deep-sky targets (galaxies, nebulae, and clusters) models real local sky brightness right now — your Bortle estimate plus the moon's actual position and phase, via the Krisciunas & Schaefer (1991) scattering model — then checks it against each object's surface brightness (galaxies/nebulae) or a sky-brightness-adjusted telescopic limit (star clusters and doubles, which shrug off light pollution far better than diffuse light). Most galaxies/nebulae use whole-object average surface brightness, which understates anything with a bright compact core or rim — M31 and M27 use their real, brighter core/rim values instead, so a plain galaxy tagged "washed out" may still show a faint nucleus. It also assumes a typical clear-night extinction coefficient, not a measurement of your actual air that night — treat close calls as "worth a look," not gospel.

Sources. Site point: Census 2024 Gazetteer, ZCTA 98374. Eclipse dates: timeanddate.com. Planet magnitudes: Mallama & Hilton (2018). Sky brightness: Krisciunas & Schaefer (1991). Cloud, visibility, wind, and CAPE: Open-Meteo, cross-checked against Clear Outside. Sky darkness: lightpollutionmap.info. Satellite elements: CelesTrak GP data, propagated with near-Earth SGP4. Pass brightness is an estimate. If that fetch fails, the page says so and links to Heavens-Above instead of inventing a time.