Comet Book vs DISCS
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
Read full descriptionHide 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.
DISCS
Contribute observations about local crop conditions and drought impacts to a scientific community. View your reports alongside data from NASA satellites, NOAA rainfall, and ground sensors.
- Report crop conditions
- Upload photos
- View drought data
- See rainfall information
- Monitor vegetation health
- Observe satellite data
Read full descriptionHide full description
The smartphone app “Drought Information Supported by Citizen Scientists” (DISCS) was created by researchers at NASA’s Marshall Space Flight Center to facilitate the sharing and delivery of hydrologic and agricultural information from citizen scientists to the scientific community and partners involved in the monitoring of drought conditions. Users, as Citizen Scientists, are encouraged to contribute photos of local crop conditions along with information about crop type, crop health, soil moisture conditions, and other notes about drought impacts. In exchange, users of the app can observe their reports alongside reports of other Citizen Scientists, and view their information in the context of drought information from the U.S. Drought Monitor, recent rainfall data from NOAA, soil moisture information from ground sensors or through NASA modeling approaches, and view information about vegetation health and stress as observed from NASA’s constellation of satellites.
Screenshots
Verdict
The clearest difference is rating: Comet Book at 5.0 against DISCS's 2.0. DISCS's advantage is update cadence (every 2 months vs every 6 months) and iOS requirement (8.0 vs 12.0). On price, review sentiment, 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.
Comet Book holds the better App Store score, 5.0 against 2.0. 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 50% of DISCS's.
Comet Book ships an update every 6 months, DISCS every 2 months. The most recent releases landed on October 23, 2026 and October 1, 2026 respectively.
| Parameter | Comet Book | DISCS |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (3 ratings) — better | 2.0 (3 ratings) |
| Positive reviews | 54.9% of reviews — better | 50.0% of reviews |
| Number of ratings | 3 | 3 |
| Update frequency | Every 6 months | Every 2 months — 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 | 54 MB |
| Age rating | 9+ | 4+ |
| Developer | Vixen Co.,Ltd. | NASA |
Customer experience
Comet Book
DISCS
In-app purchases
Comet Book
No in-app purchases
DISCS
No in-app purchases









