# Astro Locator vs Decay calc

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.

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.

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.

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

## The numbers

| Metric | Astro Locator | Decay calc |
| --- | --- | --- |
| Price | $3.99 | **Free** |
| Rating | **[4.8 (68 ratings)](https://appshunter.io/ios/app/astro-locator/id927483920/reviews)** | [1.0 (1 ratings)](https://appshunter.io/ios/app/decay-calc/id1479526735/reviews) |
| Number of ratings | **68** | 1 |
| Positive reviews | **77.3% of reviews** | 50.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 3 months | Every 3 months |
| Monetization | **Free** | Free with in-app purchases |
| Size | 6 MB | 27 MB |
| Requires iOS | 18.0 | **15.2** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 12+ | 17+ |
| Developer | [Progress Concepts Limited](https://appshunter.io/developer/788761727) | [Alexey Baranov](https://appshunter.io/developer/1479526734) |

## What reviewers say

### Astro Locator

[App page](https://appshunter.io/ios/app/astro-locator/id927483920)

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

**In-app purchases:** none


### Decay calc

[App page](https://appshunter.io/ios/app/decay-calc/id1479526735)

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:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Radio calc | $0.99 | one-time |


## Frequently asked 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.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*