Comparison

Astro Locator vs Decay calc

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

Head to head
About

Astro Locator

This app assists astronomers in quickly and easily achieving polar alignment for their telescopes. It helps locate key stars like Polaris or Sigma Octantis, displaying essential astronomical data for setup and viewing. Ideal for mobile astronomers who frequently set up and pack down their equipment.

Highlights
  • Quick polar alignment
  • Locate Polaris/Sigma Octantis
  • Display elevation, latitude, longitude
  • Show moon phase
  • Sunrise/sunset times
  • Astro twilight times
  • Today Extension widget
Read full description

Spend less time setting up and more time observing. Astro Locator helps you quickly and accurately polar align your equatorial mount by showing the precise position of Polaris or Sigma Octantis. Designed for both visual astronomy and astrophotography, it makes polar alignment fast, simple and reliable wherever you observe. Whether you’re setting up in your garden or under dark skies, Astro Locator provides all the information you need on a single, easy-to-read screen. Features include: • Accurate Polaris and Sigma Octantis positioning • Compass direction and correct elevation for your location • Latitude, longitude and altitude • UTC and local time • Sunrise and sunset times • Astronomical twilight start and end times • Current moon phase • Clean, uncluttered interface designed for fast setup Astro Locator is ideal for astronomers who assemble and pack away their equipment for each observing session, helping you spend less time setting up and more time enjoying the night sky. Trusted by amateur astronomers since 2014.

About

Decay calc

This tool calculates the decay of radioactive isotopes over time, considering half-life for accurate activity predictions. It's useful in nuclear medicine, environmental monitoring, and radiation safety for handling and disposal of materials.

Highlights
  • Radioactive isotope decay calculation
  • Half-life integration
  • Activity prediction
  • Decay constant determination
  • Radiation dose calculation
Features
Read full description

Decay calc is a tool used to calculate the decay of radioactive isotopes over time. It takes into account the half-life of the isotope and allows for accurate predictions of the remaining activity of the isotope at any given time. Decay calc can be used in a variety of fields, such as nuclear medicine, environmental monitoring, and radiation safety. It can help determine the appropriate handling and disposal of radioactive materials and ensure the safety of individuals who may come into contact with them. In addition to calculating the remaining activity of the isotope, decay calc can also be used to determine the decay constant, which is a measure of the rate at which the isotope decays. This information can be used to calculate the radiation dose received by individuals who are exposed to the isotope. Overall, decay calc is a useful tool for anyone working with radioactive materials or interested in learning more about radioactivity and its effects. It provides accurate and reliable calculations that can help ensure safety and proper handling of radioactive materials.

Screenshots

Astro Locator2 screens
Decay calc3 screens

Verdict

The call

The clearest difference is price: Decay calc at Free against Astro Locator's $3.99. Decay calc also leads on iOS requirement (15.2 vs 18.0). Astro Locator's advantage is rating (4.8 vs 1.0) and in-app purchases (none vs 1). 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

Decay calc is free to download; Astro Locator costs $3.99 up front. Decay calc sells 1 one-off in-app purchase. Astro Locator asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Astro Locator holds the better App Store score, 4.8 against 1.0. That said, the two scores are not equally well evidenced: Astro Locator has 68 ratings behind it against 1, so its average is the more settled of the two. Written reviews point the same way: 77% of Astro Locator's written reviews are positive against 50% of Decay calc's.

UpkeepUpdate frequency

Both ship on a similar rhythm, roughly every 3 months. The most recent releases landed on November 6, 2026 and November 3, 2026 respectively.

Scorecard7 real differences · 3 level
Astro Locator versus Decay calc: the parameters behind the verdict, then further details
ParameterAstro LocatorDecay calc
Price$3.99Free — better
Rating4.8 (68 ratings) — better1.0 (1 ratings)
Positive reviews77.3% of reviews — better50.0% of reviews
Number of ratings68 — better1
Update frequencyEvery 3 monthsEvery 3 months
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhone, iPadiPhone, iPad, iPod — better
Requires iOS18.015.2 — better
Further details — not scored
Size6 MB27 MB
Age rating12+17+
DeveloperProgress Concepts LimitedAlexey Baranov

Customer experience

Astro Locator

All ratings68 ratings
Positive97.1%
Neutral0.0%
Negative2.9%
Written reviews22 reviews
Positive77.3%
Neutral0.0%
Negative22.7%

Decay calc

All ratings1 ratings
Positive0.0%
Neutral0.0%
Negative100.0%
Written reviews4 reviews
Positive50.0%
Neutral0.0%
Negative50.0%

In-app purchases

None

Astro Locator

No in-app purchases

1 purchases

Decay calc

One-time1
  • Radio calc$0.99

Questions

Is Astro Locator free?
Astro Locator costs $3.99, with no in-app purchases.
Is Decay calc free?
Decay calc is free to download, with in-app purchases available.
Which has better reviews, Astro Locator or Decay calc?
Astro Locator is rated higher. Astro Locator averages 4.8 out of 5 from 68 ratings, while Decay calc averages 1.0 from 1 ratings.
Do Astro Locator or Decay calc have ads?
Neither Astro Locator nor Decay calc shows ads.
Which is updated more often, Astro Locator or Decay calc?
Astro Locator ships an update every 3 months, and Decay calc every 3 months. Most recently, Astro Locator was updated on November 6, 2026 and Decay calc on November 3, 2026.

Other comparisons