Sidereal: Deep Sky Atlas

Update guide

Version 3.0 (build 3)

This guide covers version 3.0. The current website catalog lists version 3.0. Check the App Store for availability on your device; the features below require version 3.0 or later.

Sidereal is an offline sky atlas and observing notebook for iPhone and iPad. Explore the sky, plan a night with your equipment, and keep your observing records together.

NEW IN 3.0 • Export and import your observing library: lists, night plans, equipment profiles and log entries. • Recover recently removed personal records. • Search lists, plans and observations, with summaries based on your saved log. • Improved saved-data protection, proper observing-site time zones, corrected Pluto calculations and restored Caldwell identifiers.

EXPLORE OFFLINE Browse 328,662 stars to magnitude 10.5 and 13,371 deep-sky catalog entries. The bundled collections include 109 distinct Messier entries and all 109 Caldwell entries. M102’s historical identity is disputed; NGC 5866 remains searchable by designation.

Pan and zoom the sky chart, inspect object details, and view constellation lines and boundaries, an altitude/azimuth grid, the ecliptic and solar-system objects. Change the observing time to explore the sky at your chosen site.

PLAN AND RECORD Night Run Studio ranks candidates using your location, selected time and equipment assumptions. Save a field plan and mark completed stops. Keep observing lists and log notes for equipment, seeing and transparency.

FIELD TOOLS Calculate imaging and visual fields of view, magnification and exit pupil. View sidereal time, Julian date and polar-alignment guidance. Switch to red night mode for observing.

UNDERSTAND THE LIMITS Calculations are planning estimates. Rise/set times assume a standard horizon and atmosphere. Lunar positions are geocentric and omit observer parallax; Pluto’s fitted model is intended for 1800–2050. Scores do not measure weather or guarantee visibility. Models & Accuracy explains the methods.

YOUR RECORDS No account, ads, subscription or in-app unlocks. Personal records stay on device unless you choose to export or share. Backups include lists, plans, equipment and log entries, but not site/display settings or recently removed records. Import validates files up to 25 MB and preserves conflicting records as separate copies.

Guide updated 2026-11-01.