Sidereal: Deep Sky Atlas

About Sidereal: Deep Sky Atlas

Sidereal is a serious, offline sky atlas and observation planner built for amateur astronomers and astrophotographers — not another horoscope or AR toy. Every star position, rise time, and planetary coordinate is computed on your device from bundled professional catalogs, so it works perfectly at a dark site with no cell signal.

A REAL CATALOG IN YOUR POCKET
• 328,000 stars down to magnitude 10 (Hipparcos / ATHYG), with proper names, Bayer and Flamsteed designations, spectral types, distances and luminosities
• 13,000+ deep-sky objects — the complete NGC and IC catalogs
• The full Messier catalog and the Caldwell catalog, curated for observers
• Constellation stick figures, IAU boundaries and full constellation reference
• Everything is bundled and offline — no account, no cloud, no tracking

INTERACTIVE SKY CHART
• Pan and pinch a live planetarium view of the sky from your exact location and time
• Stars sized by magnitude and tinted by colour index; deep-sky objects drawn by type
• Constellation lines and labels, the ecliptic, an alt-azimuth grid and a true horizon with cardinal points
• Planets, the Sun and the Moon plotted from real ephemerides
• Tap anything to identify it and open a full data sheet
• Scrub time forward or back to see how the sky moves

PRECISE POSITIONAL ASTRONOMY
• Rise, transit and set times, plus an altitude curve for any object across the night
• Astronomical, nautical and civil twilight, and hours of true darkness
• Precession, nutation, sidereal time and apparent (of-date) coordinates
• Planetary and solar positions from the VSOP87 theory; lunar position, phase and illumination from an ELP-2000 series — all evaluated on device

PLAN YOUR NIGHT
• Tonight view: sunset to sunrise, moon phase and interference, planet visibility
• The best Messier and Caldwell targets tonight, ranked by altitude during darkness and distance from the Moon
• Observing lists you build yourself, and a session log for seeing, transparency, equipment and notes

TOOLS FOR THE FIELD
• Imaging field-of-view and image-scale calculator for any telescope and camera
• Visual field-of-view, magnification and exit-pupil calculator for eyepieces
• Polar-alignment helper with a live Polaris reticle clock position
• Local and Greenwich sidereal time, Julian date and obliquity

BUILT FOR THE DARK
• Red-light night mode preserves your dark adaptation
• Choose your site by GPS or enter coordinates for anywhere on Earth

Sidereal keeps your observing entirely private and entirely on your device. Own it — no login, no subscription round-trips, no light pollution of your data.