Comet Book vs 星空ナビ
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Comet Book
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.
- Comet viewing direction and elevation
- Real-time celestial object tracking
- 3D Solar System mode
- Visualize comet and planet motion
- Observing site guidance
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The Comet Book app clearly shows when Comets can be viewed and in which direction. The direction and elevation of a Comet can change noticeably in a day due to its fast apparent motion. The moon and a bright planet may be convenient as a guide to find the comet though they have large apparent motion, too. This app determines where Comet is in the sky when it becomes visible at your observing site. You can easily start your observation of a Comet by using Comet Book as a guide to the direction and elevation of the comet. In addition, the new “3D Solar System seen from Space” mode allows you to view the motion of Comets and planets turning around the sun. Please take a look the comet’s movement around our solar system.
星空ナビ
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「星空ナビ」は、星空の「今」がわかる新しい星空アプリです。ぜひ見ておきたい星空の景色から、近く見られる天文現象、神秘的な宇宙の話題まで、不思議がいっぱいの星空を思いきり楽しめます。 夕方の空にうかぶ三日月、明るく輝く宵の明星、光跡を残しながら流れる流星群、宇宙の神秘を感じさせる日食や月食といった天文現象はもちろん、最近発見された新しい星や目には見えないブラックホール、惑星探査機が活躍するニュースなどもご覧いただけます。 「星空ナビ」で、夜空の星を感じる毎日を送ってみませんか。 利用規約：https://www.astroarts.co.jp/products/navi/terms-j.shtml
Screenshots
Verdict
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.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
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.
| Parameter | Comet Book | 星空ナビ |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (3 ratings) — better | 4.7 (3 ratings) |
| Positive reviews | 54.9% of reviews — better | 28.6% of reviews |
| Number of ratings | 3 | 3 |
| Update frequency | Every 6 months | Every 6 weeks — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Free | — |
| Devices | iPhone, iPad, iPod — better | iPhone, iPod |
| Requires iOS | 12.0 — better | 15.1 |
| Further details — not scored | ||
| Size | 10 MB | 106 MB |
| Age rating | 9+ | 4+ |
| Developer | Vixen Co.,Ltd. | AstroArts Inc. |
Customer experience
Comet Book
星空ナビ
In-app purchases
Comet Book
No in-app purchases
星空ナビ
- 有料会員（１ヶ月）1 Month trial$1.491 Month
- 有料会員（１年）$13.991 Year
