SightReduce Celestial
Offline Celestial Reduction
$4.99 · Designed for iPad. Not verified for macOS.
Reduce sextant sights to Ho, Hc, Zn, and intercept, plot the line of position, keep a passage sight book, and export the log offline.
SightReduce Celestial is a paid, local-first worksheet for offshore sailors, celestial-navigation students, instructors, and traditional navigators.
Enter an observed sextant altitude, index correction, height of eye, assumed latitude and longitude, and GHA and declination copied from your own nautical almanac. The app applies dip and standard refraction corrections, converts Hs to Ho, calculates Hc and Zn with spherical trigonometry, and derives a nautical-mile intercept with a clear Toward or Away instruction.
The reduction screen keeps each correction visible instead of hiding the result behind a single answer. Carry the calculated azimuth and intercept into the local plotting aid, which draws the intercept point and perpendicular line of position on a clean navigation grid.
Save multiple sights in a passage sight book, duplicate a full worksheet as a revision, retain observation time and notes, and export the reduction log as CSV with the original inputs and computed outputs.
SightReduce does not provide almanac ephemerides and does not replace official navigation publications or prudent cross-checking. No login is required. The app has no subscription, in-app purchases, ads, analytics, tracking, cloud sync, AI processing, or developer-server upload.
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The developer, Gobling Company, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Gobling Company
- Size
- 4.8 MB
- Category
- Navigation
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Age Rating
4+
- 4+
- Copyright
- © 2026 Gobling Company
