Comparison

Polar Scope Align Pro vs Buoyancy Calc

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

Head to head
About

Polar Scope Align Pro

This app assists astronomers with precise polar alignment for telescopes, offering tools for various reticles and low-latitude accuracy. It also includes a comprehensive suite of astro tools, from object databases to calculators and weather reports.

Highlights
  • Accurate polar alignment calculation
  • Support for numerous polar scope reticles
  • Daytime/no polarscope alignment tool
  • Deep Space Object database
  • Astrophotography calculators
  • World astro-weather report
Features
Currently charting
Read full description

Polar Scope Align Pro is a complete toolkit for amateur astronomers: accurate polar alignment, deep-sky observing, astro weather, push-to/manual GoTo, iOptron mount WiFi control, widgets and more. All features and updates are free forever. Optional in-app purchases are just tips to support development. POLAR ALIGNMENT • Calculates Polaris or σ Octantis position for 30+ reticle types: iOptron, Astro-Physics, Takahashi, Skywatcher, Vixen, Celestron, Orion, Astrotrac and others* • Atmospheric refraction correction for accuracy at any latitude • Works with or without a polar scope ALIGNMENT WITHOUT A POLAR SCOPE • Daytime / No Polar Scope Alignment: works day and night with just your phone's gyro • Camera Azimuth Calibration: use sun/moon/stars to calibrate gyro and align accurately without a compass, immune to magnetic interference • Laser / Hop Align: nighttime alignment for maximum accuracy with a laser or a scope with no view of Polaris • Live sky map guides you to the celestial pole in real time • Sun Finder helps you point your filtered telescope/telephoto to the Sun PUSH TO (MANUAL GOTO) • Attach your phone to any scope and convert it to manual/push GoTo • Select from a large database and use direct push or more accurate hop-to mode DEEP SKY OBJECT DATABASE • 22,000+ objects with altitude graphs, rise/set times and more info • Save and manage curated observing lists • Filter, search, sort and push to any target XASTERIA ASTRO WEATHER • Hourly astronomy forecasts from 7Timer, OpenWeather, MET Norway and Apple Weather, plus a configurable Multi-source forecast • Animated satellite Cloud Map with recent EUMETSAT and NASA infrared imagery • Aurora forecasts • ISS and bright satellite passes with an All Sky night chart, individual sky charts, live map tracking, and Tiangong and Hubble views • Solar eclipse tool with past and future eclipses, live mode with audio cues • Experimental eclipse camera for automated photoshoots of partial phase, diamond ring, Baily's beads, totality bracketing • Interactive light pollution map using World Atlas and recent VIIRS data CALCULATORS & TOOLS • 30+ calculators for observing and astrophotography • Moon phase calendar with altitude graphs • Solar eclipse calculator and simulator • Bubble level & Compass IOPTRON WIFI MOUNT CONTROL • Connect to WiFi-enabled iOptron mounts (HAE, HAZ, HEM, CEM, GEM and more) • Automatic date/time/location setup • Switch between Equatorial and Alt-Az on mounts that support both • Move & Sync: directional control with a live sky map • Point GoTo: aim your phone at a patch of sky and send the mount there • Current Point Query: find out what the mount is pointing at • GoTo any object from the DSO Database NIGHT-FRIENDLY • Red, green or white night mode with dimmer WIDGETS • Configurable Tonight and Multi astronomy weather forecasts • Upcoming bright satellite passes • Aurora probability, activity forecast and NOAA aurora map * Full list of supported reticles: Astro-Physics RAPAS & PASILL, iOptron, the latest Orion / Skywatcher, the Classic Skywatcher / Orion / Celestron / Meade / EXOS2 / Bresser / MSM, various versions of Takahashi EM-10/11/200/400/500, NJP, PM-1, P2-Z, the Telrad, Rigel QuikFinder, a couple for Astrotrac / Losmandy / Kenko / Avalon, the Vixen PF-L/Atlux/SX/SXD/SXP/AXD/GP/GP-DX/Polarie Polar Axis Scopes, a Konus and several Polar Finders: Tuthill, Explore Scientific 8x50, Meade 9x60, Vixen Polaris, Celestron 7x50, Carton Optical. PoleMaster help view for South Hemisphere users.

About

Buoyancy Calc

Calculate the optimal weight for scuba diving based on environmental factors. Input your weight, water type, tank, and exposure suit to get a suggested weight for neutral buoyancy.

Highlights
  • Calculate suggested diving weight
  • Adjust for water type
  • Adjust for tank type
  • Adjust for exposure suit
  • Supports pounds and kilograms
Features
Read full description

Quickly find out the suggested weight you should add when scuba diving in different environments. Based on PADI's Peak Performance Buoyancy basic weighting guideline*. Enter your weight in pounds or kilograms, and additionally set the type of water, tank, and exposure suit to dial in a suggested amount of weight to help keep you neutrally buoyant. *Note that this app and the developer are not officially a representative of PADI. This app will give the user a good estimate of the weight needed for the environment selected, but there are always adjustments needed to achieve peak performance, based on gender, physique, exposure suit age, accessories, etc.

Screenshots

Polar Scope Align Pro4 screens
Buoyancy Calc1 screens

Verdict

The call

The clearest difference is review sentiment: Polar Scope Align Pro at 97% against Buoyancy Calc's 40%. Polar Scope Align Pro also leads on rating (4.9 vs 3.1) and ratings volume (305 vs 25). Buoyancy Calc's advantage is price (Free vs $3.99) and in-app purchases (none vs 3). On update cadence, ads and device support 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

Buoyancy Calc is free to download; Polar Scope Align Pro costs $3.99 up front. Polar Scope Align Pro sells 3 one-off in-app purchases. Buoyancy Calc asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Polar Scope Align Pro holds the better App Store score, 4.9 against 3.1. That said, the two scores are not equally well evidenced: Polar Scope Align Pro has 305 ratings behind it against 25, so its average is the more settled of the two. Written reviews point the same way: 97% of Polar Scope Align Pro's written reviews are positive against 40% of Buoyancy Calc's.

UpkeepUpdate frequency

Polar Scope Align Pro ships an update every 2 months, Buoyancy Calc every 3 months. The most recent releases landed on September 22, 2026 and June 8, 2026 respectively.

Scorecard8 real differences · 3 level
Polar Scope Align Pro versus Buoyancy Calc: the parameters behind the verdict, then further details
ParameterPolar Scope Align ProBuoyancy Calc
Price$3.99Free — better
Rating4.9 (305 ratings) — better3.1 (25 ratings)
Positive reviews97.0% of reviews — better40.0% of reviews
Number of ratings305 — better25
Update frequencyEvery 2 months — betterEvery 3 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree — better
Best chart rank#58 — better
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS13.0 — better15.6
Further details — not scored
Size32 MB1 MB
Age rating4+4+
DeveloperDimitrios KechagiasEric Hamiter

Customer experience

Polar Scope Align Pro

All ratings305 ratings
Positive99.0%
Neutral0.0%
Negative1.0%
Written reviews269 reviews
Positive97.0%
Neutral0.7%
Negative2.2%

Buoyancy Calc

All ratings25 ratings
Positive44.0%
Neutral12.0%
Negative44.0%
Written reviews25 reviews
Positive40.0%
Neutral12.0%
Negative48.0%

Bugs and requests

Polar Scope Align Pro

Reported bugs

2 issues
  • Weather Updates Not Working
  • Compass Deflected by Mount

Requested features

2 requests
  • Add Observation Recording Feature
  • Add Push To Option for DSO Objects

Buoyancy Calc

Not enough reviews yet to summarise bugs or requests.

In-app purchases

3 purchases

Polar Scope Align Pro

One-time3
  • Tip 1x$0.99
  • Tip 4x$3.99
  • Tip 10x$9.99
None

Buoyancy Calc

No in-app purchases

Questions

Is Polar Scope Align Pro free?
Polar Scope Align Pro costs $3.99, and also offers in-app purchases.
Is Buoyancy Calc free?
Buoyancy Calc is free to download, with no in-app purchases.
Which has better reviews, Polar Scope Align Pro or Buoyancy Calc?
Polar Scope Align Pro is rated higher. Polar Scope Align Pro averages 4.9 out of 5 from 305 ratings, while Buoyancy Calc averages 3.1 from 25 ratings.
Do Polar Scope Align Pro or Buoyancy Calc have ads?
Neither Polar Scope Align Pro nor Buoyancy Calc shows ads.
Which is updated more often, Polar Scope Align Pro or Buoyancy Calc?
Polar Scope Align Pro ships an update every 2 months, and Buoyancy Calc every 3 months. Most recently, Polar Scope Align Pro was updated on September 22, 2026 and Buoyancy Calc on June 8, 2026.

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