Citizen Sky View vs Mars Book
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Citizen Sky View
Participate in a NASA-sponsored citizen science project to study cloud formation. Coordinate with the project team for events, then use your phone to capture images of the sky at assigned locations and times. Your contributions help researchers learn more about atmospheric science.
- Citizen science participation
- Cloud formation research
- Event coordination
- Location-based image capture
- Data contribution for research
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This application is for a citizen science project being developed at the University of Colorado at Boulder. It is sponsored by NASA and NCAR. The project requires you to coordinate with the project team to attend our upcoming events where you will be assigned a location to be at a specific time. During the event, you will have oriented your phone and placed it upside down so that it can take pictures every 30 seconds until the event is over. The team will then take these images to learn more about cloud formation.
Mars Book
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The Mars Book is an app that is dedicated for observing Mars which will make close approach in summer 2020. Mars will come close to Earth from September 2020 through October 2020. Closest approach will take place on October 6, 2020. Mars Book is a highly useful Mars observing app which will indicate the location of Mars visible in the sky. It shows you why Mars Close Approach will take place, and it is explained readily using animated illustrations and star charts at a viewpoint from outer Space. Mars Close Approaches taking place 23 times from the year 2003 through 2050 will be displayed and apparent retrograde motion of Mars will be displayed. Enjoy Mars Close Approach this summer with the Mars Book app!
Screenshots
Verdict
The clearest difference is update cadence: Citizen Sky View at every 2 weeks against Mars Book's every 13 months. 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
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
Citizen Sky View ships an update every 2 weeks, Mars Book every 13 months. The most recent releases landed on October 9, 2026 and October 26, 2026 respectively.
| Parameter | Citizen Sky View | Mars Book |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (1 ratings) — better | — |
| Number of ratings | 1 — better | — |
| Update frequency | Every 2 weeks — better | Every 13 months |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | — |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 10.3 | 9.0 — better |
| Further details — not scored | ||
| Size | 26 MB | 14 MB |
| Age rating | 4+ | 4+ |
| Developer | University of Colorado Boulder | Vixen Co.,Ltd. |
In-app purchases
Citizen Sky View
No in-app purchases
Mars Book
No in-app purchases
Questions
Is Citizen Sky View free?
Is Mars Book free?
Do Citizen Sky View or Mars Book have ads?
Which is updated more often, Citizen Sky View or Mars Book?
Other comparisons
