# Unistellar vs Cal

The clearest difference is iOS requirement: Cal at 15.1 against Unistellar's 18.0. On price, update cadence, ads and in-app purchases there is nothing between them.

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

Unistellar ships an update every 6 weeks, Cal every 3 weeks. The most recent releases landed on August 14, 2026 and September 17, 2026 respectively.

## The numbers

| Metric | Unistellar | Cal |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.8 (100 ratings)](https://appshunter.io/ios/app/unistellar/id1435141427/reviews)** | — |
| Number of ratings | **100** | — |
| Positive reviews | 44.8% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 6 weeks | **Every 3 weeks** |
| Monetization | Free | — |
| Size | 584 MB | 63 MB |
| Requires iOS | 18.0 | **15.1** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 17+ |
| Developer | [Unistellar](https://appshunter.io/developer/1384354590) | [University of California, Irvine](https://appshunter.io/developer/643200027) |

## What reviewers say

### Unistellar

[App page](https://appshunter.io/ios/app/unistellar/id1435141427)

Control your smart telescope, explore thousands of celestial objects, and observe them live. Save and share your discoveries, or contribute to real scientific research with citizen science missions.

**Highlights:** Telescope control, Explore 5000+ celestial objects, Live astronomical observation, Instant image sharing, RAW image download, Citizen science missions

**In-app purchases:** none


### Cal

[App page](https://appshunter.io/ios/app/cal-bridge-program/id6475701864)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Unistellar free?

Unistellar is free to download, with no in-app purchases.

### Is Cal free?

Cal is free to download, with no in-app purchases.

### Do Unistellar or Cal have ads?

Neither Unistellar nor Cal shows ads.

### Which is updated more often, Unistellar or Cal?

Unistellar ships an update every 6 weeks, and Cal every 3 weeks. Most recently, Unistellar was updated on August 14, 2026 and Cal on September 17, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*