Comet Book vs CassiniMIMI
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.
CassiniMIMI
Explore stunning images and data from NASA's Cassini mission to Saturn. This app provides access to energetic particle data, ENA images, and spectrograms from Saturn's magnetosphere. Discover new scientific releases and browse daily updated plots and movies.
- Energetic charged particle environment study
- Energetic Neutral Atom (ENA) imaging of Saturn
- Spectrograms and plots from particle detectors
- Access to NASA's Planetary Data System (PDS)
- Daily updated plots and movies
- Selectable data by source, type, date, and style
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NASA’s Cassini mission to Saturn has provided a unique opportunity for the Magnetospheric IMaging Instruments (MIMI) to study the energetic charged particle environment, and obtain images of Saturn using Energetic Neutral Atom (ENA) imaging. There is a rich dataset of spectrograms, plots, movies, and images that are now accessible via a dedicated iOS app. Among the data products within the MIMI suite that are viewable through the app, include the ENA images of Saturn taken with the Ion and Neutral CAmera (INCA), and spectrograms and line plots from the Low Energy Magnetospheric Measurement System (LEMMS) and CHarge Energy Mass Spectrometer (CHEMS) particle detectors. The instrument health and safety data are restricted to Cassini team members, while the calibrated science data are available to all. The CassiniMIMI app provides easy access to some of Cassini browse products that are currently in NASA’s publically accessible Planetary Data System (PDS). For some products, the public is now able to see the most up-to-date plots produced on a daily basis. Also, the public now has access to new MIMI data products that are only in the process of being released to PDS. The publically available browse products are selectable by source, type, date, style, plots, and movies. Click on the link below to checkout a description of the public menu selections, highlights of the display, samples of public plots and movies, what’s shown in the icon, and links to supporting links, including the Cassini MIMI website, instrument user’s guide, and archive at PDS.
Screenshots
Verdict
Comet Book and CassiniMIMI both sit at 5.0 stars, but that hides the real split: 100% of CassiniMIMI's written reviews are positive against 55% of Comet Book's. CassiniMIMI also leads on update cadence (weekly vs every 6 months) and iOS requirement (8.0 vs 12.0). On price, rating, ratings volume and ads 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. Neither carries in-app purchases, so what you see is what you pay.
On the App Store both sit at effectively the same score — 5.0 for Comet Book against 5.0 for CassiniMIMI. Both are backed by a comparable volume of ratings — 2 and 2 respectively. Written reviews are what separate them: 55% of Comet Book's written reviews are positive against 100% of CassiniMIMI's.
Comet Book ships an update every 6 months, CassiniMIMI weekly. The most recent releases landed on October 6, 2026 and October 8, 2026 respectively.
| Parameter | Comet Book | CassiniMIMI |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (2 ratings) | 5.0 (2 ratings) |
| Positive reviews | 54.9% of reviews | 100.0% of reviews — better |
| Number of ratings | 2 | 2 |
| Update frequency | Every 6 months | Weekly — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 12.0 | 8.0 — better |
| Further details — not scored | ||
| Size | 10 MB | 19 MB |
| Age rating | 9+ | 4+ |
| Developer | Vixen Co.,Ltd. | Johns Hopkins University Applied Physics Laboratory |
Customer experience
Comet Book
CassiniMIMI
In-app purchases
Comet Book
No in-app purchases
CassiniMIMI
No in-app purchases









