# Comet Book vs 星空ナビ

The clearest difference is in-app purchases: Comet Book at none against 星空ナビ's 2. Comet Book also leads on review sentiment (55% vs 29%) and rating (5.0 vs 4.7). 星空ナビ's advantage is update cadence (every 6 weeks vs every 6 months). On price, ratings volume, ads and device support there is nothing between them.

Both are free to download. 星空ナビ sells 2 in-app purchases, starting at $1.49 per month. Comet Book asks for nothing beyond the download.

Comet Book holds the better App Store score, 5.0 against 4.7. Both are backed by a comparable volume of ratings — 3 and 3 respectively. Written reviews point the same way: 55% of Comet Book's written reviews are positive against 29% of 星空ナビ's.

Comet Book ships an update every 6 months, 星空ナビ every 6 weeks. The most recent releases landed on October 23, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | Comet Book | 星空ナビ |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (3 ratings)](https://appshunter.io/ios/app/comet-book/id604782335/reviews)** | [4.7 (3 ratings)](https://appshunter.io/ios/app/id1437609381/reviews) |
| Number of ratings | 3 | 3 |
| Positive reviews | **54.9% of reviews** | 28.6% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 6 months | **Every 6 weeks** |
| Monetization | Free | — |
| Size | 10 MB | 106 MB |
| Requires iOS | **12.0** | 15.1 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 9+ | 4+ |
| Developer | [Vixen Co.,Ltd.](https://appshunter.io/developer/536188843) | [AstroArts Inc.](https://appshunter.io/developer/293118838) |

## What reviewers say

### Comet Book

[App page](https://appshunter.io/ios/app/comet-book/id604782335)

Discover and track comets with this educational app. It provides real-time direction and elevation data to help you locate celestial objects in the night sky. Explore the solar system in 3D and visualize the movement of comets and planets.

**Highlights:** Comet viewing direction and elevation, Real-time celestial object tracking, 3D Solar System mode, Visualize comet and planet motion, Observing site guidance

**In-app purchases:** none


### 星空ナビ

[App page](https://appshunter.io/ios/app/id1437609381)

**Features:** Vision Pro support

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 有料会員（１ヶ月） | $1.49 | per month |
| 有料会員（１年） | $13.99 | per year |


## Frequently asked questions

### Is Comet Book free?

Comet Book is free to download, with no in-app purchases.

### Is 星空ナビ free?

星空ナビ is free to download, with in-app purchases available.

### Which has better reviews, Comet Book or 星空ナビ?

Comet Book is rated higher. Comet Book averages 5.0 out of 5 from 3 ratings, while 星空ナビ averages 4.7 from 3 ratings.

### Do Comet Book or 星空ナビ have ads?

Neither Comet Book nor 星空ナビ shows ads.

### Which is updated more often, Comet Book or 星空ナビ?

Comet Book ships an update every 6 months, and 星空ナビ every 6 weeks. Most recently, Comet Book was updated on October 23, 2026 and 星空ナビ on October 24, 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.*