Comparison

Celestial Nav vs Rule Master

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Celestial Nav

This app provides tools for celestial navigation, offering computations for celestial bodies and sight reductions. It includes an offline perpetual almanac and allows for quick capture of observation data for accurate course adjustments.

Highlights
  • Celestial navigational computations
  • Offline perpetual almanac
  • Quick celestial observation data capture
  • High accuracy sight reductions
  • Sight planning and reduction tools
  • Celestial fix computations
Features
Read full description

We believe celestial navigation is an amazing skill and develop Celestial Nav to offer a simple, yet powerful and all encompassing app for our users. Celestial Nav is an easy to use, all-in-one tool which offers: • Celestial navigational computations for your device • Simple toolbar menu for quick access • Internally stored perpetual Almanac • Offline ready and functional without the need for other external tools • Quick and easy capture celestial observation data • High accuracy sight reductions • Star reference tables SIGHT PLANNING • Local Hour Angle (LHA) for Aries • Star tables sorted by name, magnitude, declination, and SHA • Sunrise, sunset, twilight, and location reference • Moon phase reference SIGHT REDUCTION • High accuracy sight reduction algorithm • Perpetual Almanac offering accurate data for years 1600 - 3000 • Almanac data for Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn • Detailed Almanac data for 58 navigational stars • Assumed Position (AP) for any user defined position • Line of Position (LOP) intercept data for accurate course and speed adjustments • Computational variables displayed for accuracy and validation CELESTIAL FIX • Computations by USNO algorithm in the Nautical Almanac • Save all your LOP in an easy reference table BASIC VERSION Free daytime celestial navigation tools using the sun: • Unlimited sextant sight reduction calculations • Sight reduction to a line of position using the sun • Perpetual almanac for the sun • Advanced sight corrections for index error, eye height, temperature, and pressure • Support for upper and lower limb reference • Star Table with navigational references • Detailed Sun references • Limited Moon references PRO FEATURES (IN-APP PURCHASE) Advanced Day & Night Celestial Navigation includes all BASIC features plus: • Almanac data for 65 navigational bodies for years 1600 through 3000 • Map display for saved LOPs • View intercepts with course and speed corrections • Metric and imperial unit support with automatic conversions • Support for coordinate entries in different formats (H° M’ S” or Decimals) • Save all your LOP calculations for future reference • Save user preferences and settings • Unrestricted moon references • Almanac and algorithmic models for 65 navigational bodies: • Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn • 58 navigational stars Supported stars: Acamar, Achernar, Acrux, Adhara, Aldebaran, Alioth, Alkaid, Alnair, Alnilam, Alphard, Alphecca, Alpheratz, Altair, Ankaa, Antares, Arcturus, Atria, Avior, Bellatrix, Betelgeuse, Canopus, Capella, Deneb, Denebola, Diphda, Dubhe, Elnath, Eltanin, Enif, Fomalhaut, Gacrux, Gienah, Hadar, Hamal, Kaus Australis, Kochab, Markab, Menkar, Menkent, Miaplacidus, Mirfak, Nunki, Peacock, Polaris, Pollux, Procyon, Rasalhague, Regulus, Rigel, Rigil Kent., Sabik, Schedar, Shaula, Sirius, Spica, Suhail, Vega, Zubengenubi REFERENCES Sight reductions and celestial calculations use various internationally accepted references for the most accurate results: • Jean Meeus - Astronomical Algorithms • US Naval Observatory (USNO) Almanac and Algorithms • Hipparcos New Astrometric Catalog, Published 2007 • ELP2000-85 SUBSCRIPTION TERMS Celestial Nav is free to download and the basic features free to use. A paid upgrade to the PRO version provides access to premium features and additional tools. We may offer trial subscriptions that give limited time access to all PRO features and premium content for the duration of the trial period. Trial subscriptions automatically expire and the app will revert back to the Basic version thereafter. No data is lost but access and use of premium features will no longer be available.

About

Rule Master

Master maritime navigation rules with this comprehensive quiz app. It offers extensive question banks, custom filters, and detailed progress tracking for both new and experienced sailors. Generate custom exams and access a digital handbook for efficient learning and exam preparation.

Highlights
  • 10,000+ question-answer combinations
  • Custom question filters
  • Fill-in-the-blank questions
  • Offline capability
  • Exam PDF generation
  • Digital Navigation Rules handbook
  • Progress tracking and statistics
Features
Currently charting
Read full description

The most advanced, modern, and competitive Rules of the Road quiz application on the iOS App Store! This Navigation Rules quiz application is a must-have for new and experienced sailors, alike. This complete Rules of the Road toolbox is the most effective way to build and maintain proficiency, so you can spend less time preparing for your next USCG Navigation Rules examination. Track your progress like never before, and use our advanced question filters and rule proficiency statistics for efficient, targeted studying. Are you an instructor? Generate and print beautiful, custom-filtered COLREG examinations in seconds with our advanced exam PDF generation algorithm. Are you an experienced mariner? There is always more to learn! Rule Master provides 100+ hand-selected, fill-in-the-blank questions optimized to refine your mastery of the Rules of the Road. Mastery of these verbatim COLREG excerpts allows for intelligent verbal communication of the rules — especially useful for students undergoing rigorous training at the USN Mariner Skills Training Command. - 10,000+ question-answer combinations - Advanced, custom question filters for targeted studying - 100+ hand-selected, fill-in-the-blank questions for experienced Mariners - Full offline capability - Unlimited exam PDF generation and printing - Full, digital Navigation Rules handbook for quick reference - In-depth progress tracking and statistics This COLREG application's abbreviated question bank -- tediously hand-scrubbed and optimized by an experienced USN Surface Warfare Officer -- is coupled with a custom algorithm that generates 10,000+ unique question-answer combinations specifically designed to more effectively teach and examine student knowledge while simultaneously exposing students to the confusing vernacular commonly found in the infamous USCG Rules of the Road question bank.

Screenshots

Celestial Nav4 screens
Rule Master4 screens

Verdict

The call

The clearest difference is price: Celestial Nav at Free against Rule Master's $9.99. Celestial Nav also leads on review sentiment (64% vs 43%) and update cadence (every 3 weeks vs every 3 months). Rule Master's advantage is rating (4.8 vs 4.3) and in-app purchases (none vs 6). On ads, monetization model and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Celestial Nav is free to download; Rule Master costs $9.99 up front. Celestial Nav sells 6 in-app purchases, starting at $1.99 per month. Rule Master asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Rule Master holds the better App Store score, 4.8 against 4.3. That said, the two scores are not equally well evidenced: Rule Master has 292 ratings behind it against 10, so its average is the more settled of the two. Written reviews complicate that: 64% of Celestial Nav's written reviews are positive against 43% of Rule Master's, so the app with the better star average is not the one people write more warmly about.

UpkeepUpdate frequency

Celestial Nav ships an update every 3 weeks, Rule Master every 3 months. The most recent releases landed on October 1, 2026 and October 11, 2026 respectively.

Scorecard8 real differences · 3 level
Celestial Nav versus Rule Master: the parameters behind the verdict, then further details
ParameterCelestial NavRule Master
PriceFree — better$9.99
Rating4.3 (10 ratings)4.8 (292 ratings) — better
Positive reviews64.3% of reviews — better42.9% of reviews
Number of ratings10292 — better
Update frequencyEvery 3 weeks — betterEvery 3 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree with in-app purchases
Best chart rank—#199 — better
DevicesiPhone, iPad, iPod — betteriPhone
Requires iOS15.0 — better16.0
Further details — not scored
Size20 MB13 MB
Age rating4+4+
DeveloperSkytip LLCUniversal Queue LLC

Customer experience

Celestial Nav

All ratings10 ratings
Positive80.0%
Neutral10.0%
Negative10.0%
Written reviews14 reviews
Positive64.3%
Neutral7.1%
Negative28.6%

Rule Master

All ratings292 ratings
Positive94.9%
Neutral3.8%
Negative1.4%
Written reviews14 reviews
Positive42.9%
Neutral28.6%
Negative28.6%

Bugs and requests

Celestial Nav

Not enough reviews yet to summarise bugs or requests.

Rule Master

Reported bugs

5 issues
  • Questions disappear off the bottom of the screen
  • Diagrams are too small to identify vessels
  • Some questions have character limits over the margin
  • App doesn't display quiz and verbatim in a usable manner
  • Incomplete questions showing three dots (...)

Requested features

4 requests
  • Link relevant COLREG rule when answering correctly and incorrectly
  • Expand subjects to include chemistry or history
  • Improvements in tracking missed questions for training
  • Display full question text when it's cut off

In-app purchases

6 purchases

Celestial Nav

Subscriptions3
  • PRO Version$1.991 Month
  • PRO Version$7.996 Months
  • PRO Version$9.991 Year
One-time3
  • 7 Day Trial License$0.99
  • 30 Day Trial License$2.99
  • PRO Version Lifetime$24.99
None

Rule Master

No in-app purchases

Questions

Is Celestial Nav free?
Celestial Nav is free to download, with in-app purchases available.
Is Rule Master free?
Rule Master costs $9.99, with no in-app purchases.
Which has better reviews, Celestial Nav or Rule Master?
Rule Master is rated higher. Celestial Nav averages 4.3 out of 5 from 10 ratings, while Rule Master averages 4.8 from 292 ratings.
Do Celestial Nav or Rule Master have ads?
Neither Celestial Nav nor Rule Master shows ads.
Which is updated more often, Celestial Nav or Rule Master?
Celestial Nav ships an update every 3 weeks, and Rule Master every 3 months. Most recently, Celestial Nav was updated on October 1, 2026 and Rule Master on October 11, 2026.

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