Comparison

Comet Book vs GeoMemorizer

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

Head to head
About

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.

Highlights
  • Comet viewing direction and elevation
  • Real-time celestial object tracking
  • 3D Solar System mode
  • Visualize comet and planet motion
  • Observing site guidance
Read full description

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.

About

GeoMemorizer

Features
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GeoMemorizer は、日本の地理を「地図の上で」覚えるための学習アプリです。 白地図に並んだ地名・川・山・鉄道・道路の名前を、3つのモードでくり返し練習できます。 ■ 覚えられる項目 ・地名記憶 … 都道府県名(47)、市区町村名(全国1,747。都道府県を選ぶと、その地図に拡大します) ・河川名記憶 … 一級河川名(全国109水系の本川) ・山名記憶 … 100名山、標高3000m以上、2500m以上3000m未満、2000m以上2500m未満 ・鉄道・駅名記憶 … 新幹線・JR・私鉄の路線名と駅名(路線を選ぶと、その路線の駅に拡大します) ・道路名記憶 … 高速道路名、高速道路のIC・JCT名、国道番号 ■ 3つのモード ・表示モード … すべての名前とふりがなを表示。地図を眺めて覚えます ・記憶モード … 名前は隠れています。タップすると名前が表示され、もう一度タップで隠れます ・記入モード … タップして名前を入力。正解は緑、不正解は赤。全部正解すると「おめでとう!!」 記入の結果は、「リセット」を押すまで保存されます ■ 特長 ・名前の下にふりがなを表示。読み方の分からない地名や駅も覚えられます ・鉄道は路線の色、国道・高速道路も色分けして表示 ・ピンチで拡大・縮小、なぞって移動。地図アプリと同じ感覚で操作できます ・ダークモードに対応 ・通信を行わず、端末の中だけで動作。さくさく動きます ・個人情報や利用状況を集めることはありません ■ データの出典 ・国土数値情報(行政区域データ・鉄道データ・高速道路時系列データ)(国土交通省)を加工して作成 ・「地球地図日本」「日本の主な山岳標高」、地理院地図ベクトル(国土地理院)を加工して作成 ・読み: 総務省「全国地方公共団体コード」、国土交通省「河川整備基本方針」、Wikidata、Wikipedia

Screenshots

Comet Book2 screens
GeoMemorizer4 screens

Verdict

The call

The clearest difference is update cadence: GeoMemorizer at every 2 weeks against Comet Book's every 6 months. Comet Book's advantage is iOS requirement (12.0 vs 17.0). On price, ads, in-app purchases 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

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

Comet Book ships an update every 6 months, GeoMemorizer every 2 weeks. The most recent releases landed on November 1, 2026 and October 29, 2026 respectively.

Scorecard2 real differences · 8 level
Comet Book versus GeoMemorizer: the parameters behind the verdict, then further details
ParameterComet BookGeoMemorizer
PriceFreeFree
Rating5.0 (3 ratings) — better—
Positive reviews54.9% of reviews—
Number of ratings3 — better—
Update frequencyEvery 6 monthsEvery 2 weeks — better
AdsNoNo
In-app purchasesNoNo
MonetizationFree—
DevicesiPhone, iPad, iPod — betteriPhone, iPad
Requires iOS12.0 — better17.0
Further details — not scored
Size10 MB20 MB
Age rating9+4+
DeveloperVixen Co.,Ltd.Takafumi Nakasu

In-app purchases

None

Comet Book

No in-app purchases

None

GeoMemorizer

No in-app purchases

Questions

Is Comet Book free?
Comet Book is free to download, with no in-app purchases.
Is GeoMemorizer free?
GeoMemorizer is free to download, with no in-app purchases.
Do Comet Book or GeoMemorizer have ads?
Neither Comet Book nor GeoMemorizer shows ads.
Which is updated more often, Comet Book or GeoMemorizer?
Comet Book ships an update every 6 months, and GeoMemorizer every 2 weeks. Most recently, Comet Book was updated on November 1, 2026 and GeoMemorizer on October 29, 2026.

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