# Dragonfly Observatory Control vs AnchorChainCalculator

The clearest difference is price: Dragonfly Observatory Control at Free against AnchorChainCalculator's $12.99. Dragonfly Observatory Control also leads on iOS requirement (8.0 vs 10.0). AnchorChainCalculator's advantage is update cadence (every 3 weeks vs every 11 months). On ads, in-app purchases and device support there is nothing between them.

Dragonfly Observatory Control is free to download; AnchorChainCalculator costs $12.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Dragonfly Observatory Control ships an update every 11 months, AnchorChainCalculator every 3 weeks. The most recent releases landed on November 2, 2026 and November 3, 2026 respectively.

## The numbers

| Metric | Dragonfly Observatory Control | AnchorChainCalculator |
| --- | --- | --- |
| Price | **Free** | $12.99 |
| Rating | — | **[5.0 (5 ratings)](https://appshunter.io/ios/app/anchorchaincalculator/id1533741243/reviews)** |
| Number of ratings | — | **5** |
| Positive reviews | — | 100.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 11 months | **Every 3 weeks** |
| Monetization | — | Paid |
| Size | 33 MB | 12 MB |
| Requires iOS | **8.0** | 10.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Lunatico Astronomia S. L.](https://appshunter.io/developer/571006483) | [Mathias Wagner](https://appshunter.io/developer/1533741245) |

## What reviewers say

### Dragonfly Observatory Control

[App page](https://appshunter.io/ios/app/dragonfly-observatory-control/id1229088380)

**Features:** macOS Compatibility

**In-app purchases:** none


### AnchorChainCalculator

[App page](https://appshunter.io/ios/app/anchorchaincalculator/id1533741243)

Calculate the optimal amount of anchor chain or rope for secure anchoring based on vessel characteristics and sea conditions. Provides detailed load calculations and accounts for dynamic effects like swell and gusts. Supports both metric and imperial units, with options for chain-only or mixed rope/chain setups.

**Highlights:** Physics-based anchoring calculations, Customizable vessel and sea conditions, Chain-only or mixed rope/chain support, Load and swell absorption analysis, Metric and imperial unit support, Multiple vessel configuration storage, Basic and Expert modes

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Dragonfly Observatory Control free?

Dragonfly Observatory Control is free to download, with no in-app purchases.

### Is AnchorChainCalculator free?

AnchorChainCalculator costs $12.99, with no in-app purchases.

### Do Dragonfly Observatory Control or AnchorChainCalculator have ads?

Neither Dragonfly Observatory Control nor AnchorChainCalculator shows ads.

### Which is updated more often, Dragonfly Observatory Control or AnchorChainCalculator?

Dragonfly Observatory Control ships an update every 11 months, and AnchorChainCalculator every 3 weeks. Most recently, Dragonfly Observatory Control was updated on November 2, 2026 and AnchorChainCalculator 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.*