# iCSC: Clear Sky Chart Viewer — Astronomy forecasts for all

> Astronomy weather forecasts for optimal sky observation. (iPhone/iPad app by Random Widgets LLC.)

- Source: https://appshunter.io/ios/app/icsc-clear-sky-chart-viewer/id877416121 (this page in markdown: same URL + `.md`)
- Developer: [Random Widgets LLC](https://appshunter.io/developer/1689907576)
- Category: Weather, Education
- Price: Free
- Rating: 4.80/5 from 1,548 App Store ratings · 94 written reviews indexed
- Age rating: 4+
- Requires: iOS 11.0 · 19 MB
- Languages: American English
- Released: 2014-06-22
- Data updated: 2026-08-28
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/icsc-clear-sky-chart-viewer/id877416121/reviews.md

## What is iCSC?

Choosing when and where to observe is hard. It's a pain to take out your telescope and then having to put it away when clouds quickly roll in. 

Well, now you don't have to. With iCSC on your iPhone, you can easily search around for the best location, using Clear Sky Charts published by Attilla Danko.

The Clear Sky Chart, invented and maintained by Attilla Danko, shows at a glance when, in the next 48 hours, one might expect clear and dark skies for a specific observing site.

There are over 4600 charts available for North America, with data provided by Allan Rahill of the Canadian Meteorological Center. These charts provide Cloud Cover, Transparency, Seeing, Darkness, Wind, Humidity, and Temperature. Users can also enable a legend to help read the charts.

iCSC allows users to find charts by title, location, or with a map. Users can then save the charts that they use often. 

While Clear Sky Charts are targeted at astronomers, anyone who wishes to look into the heavens, or needs a highly accurate sky forecast can benefit from iCSC: Clear Sky Chart Viewer.

## Key features

- 48-hour sky forecasts
- Cloud cover, transparency, seeing data
- Search by location or map
- Save favorite charts
- Legend for chart interpretation
- North American chart coverage

## What do users think of iCSC?

Overall sentiment: positive

**Pros**

- 🚀 Awesome
- 🚀 Great
- 🚀 The Best
- 🚀 Great Tool
- 🚀 Works Great !
- 🚀 Must have for astronomy!
- 🚀 Great for everyday use
- 🚀 It works and it is easy to use
- 🚀 Very Accurate!
- 🚀 Indispensabile
- 🚀 Basic but Useful
- 🚀 Best app for dark sky forecast
- 🚀 Fantastic
- 🚀 Extremely accurate!
- 🚀 Hidden Gem
- 🚀 Just as good as the website but easier
- 🚀 Excellent!!!
- 🚀 Essential astronomy tool!
- 🚀 Accurate and easy to use
- 🚀 Amazing
- 🚀 Nice
- 🚀 Best Weather App for Astronomers!
- 🚀 A must-have tool
- 🚀 Almost perfect
- 🚀 Easy to retrieve multiple astro forecasts
- 🚀 This new version is better
- 🚀 More than just astronomy..
- 🚀 5 star

**Cons**

- 🐛 Not supported
- 🐛 Accuracy
- 🐛 no key to charts
- 🐛 NO TOO IMPRESSED
- 🐛 Terrible.
- 🐛 Never Right!
- 🐛 Limited scope
- 🐛 Pretty Good
- 🐛 Good, but glaring issue!
- 🐛 Horrible interface to useful data

**Commonly reported bugs**

- Crashed on opening a favorite, even after your message says bug is fixed.
- Latest update crashes on Iphone X
- Crashes as soon as I select an observatory/location ever since the update.
- Wish they explained what each category meant in terms of overall ability to see the stars.
- The data isn't bad, but it is all but unusable on my 5th gen iPad Pro 12.9. Tiny text you can't zoom in on.

**Most requested features**

- Please add widgets and iPad support
- Can update the forecast more frequent, at least once in the afrernoon
- Search function
- Good app, would love widget

## Recent user reviews (10 of 94)

All indexed reviews: https://appshunter.io/ios/app/icsc-clear-sky-chart-viewer/id877416121/reviews.md

### 4/5 — Used for long time now crashes

*2026-08-01, version 1.2.5*

iPhone 15 pro max, worked for long time now crashes 1 sec after starting. Reinstalled, no help.

### 5/5 — Awesome

*2026-01-05, version 1.2.5*

Totally awesome

### 4/5 — Great

*2025-11-29, version 1.2.5*

Nice little app to see the weather forecast for observations

### 1/5 — Not supported

*2025-09-26, version 1.2.5*

Does kit seem like they support the app anymore.  No updates.  App did not update the weather this week.

### 5/5 — The Best

*2025-09-25, version 1.2.5*

Hands down the best forecast for astronomy…ever

### 1/5 — The world isn’t just North America

*2025-08-17, version 1.2.5*

Would have been nice to get a chart for Puerto Rico.

### 5/5 — Great Tool

*2025-08-06, version 1.2.5*

Great tool. I’m a novice at astrophotography so this app / website is essential. And it is great.

### 5/5 — Works Great !

*2025-05-22, version 1.2.5*

I’ve been a Clear Sky user for several years - much more reliable than any other tool I’ve used for astronomical forecasting

### 2/5 — Accuracy

*2025-05-17, version 1.2.5*

Cloud cover about 50% yet says clear Wagoner, OK

### 3/5 — Not supported

*2025-01-03, version 1.2.5*

Does kit seem like they support the app anymore.  No updates.  App did not update the weather this week.

## Frequently asked questions about iCSC

### What does iCSC: Clear Sky Chart Viewer do?

This app provides detailed 48-hour forecasts for sky conditions, specifically designed for astronomical observation. It helps users determine the best times and locations for clear, dark skies by displaying various weather and atmospheric data.

### What kind of data does the app provide?

The app displays data from Clear Sky Charts, including Cloud Cover, Transparency, Seeing, Darkness, Wind, Humidity, and Temperature. It also offers a legend to help users interpret the charts.

### Is this app free to use?

Yes, based on the provided information, the app is free to use and does not feature in-app purchases or advertisements.

### Who would benefit from using this app?

The app is primarily targeted at astronomers who need to plan their observing sessions. However, anyone interested in celestial events or requiring precise sky forecasts can also benefit from its features.

### How can I find charts for my location?

You can find charts by searching for them by title or location. The app also includes a map feature to help you discover available charts for different observing sites.

## Version history (last 5 releases)

### 1.2.5 — 2018-02-26

This update from Apple will improve the functionality of this app. No new features are included.

Sorry - we let a bug slip through! The issue with favorites has been fixed.

### 1.2.4 — 2018-02-26

Updated UI and improved support for dynamic type.

Happy viewing!

### 1.2.3 — 2017-12-31

Just a small update to end the year! This update adds support for the iPhone X, improves the map, and fixes some bugs.

Please let me know if you have any issues using the in-app support form. Enjoy!

### 1.2.2 — 2017-07-17

While most are gearing up for the "Great American Eclipse" on August 21st, we are making some minor changes to iCSC. Here's what's new:

- You can now share iCSC charts to help plan observing sessions.

- Bug fixes.

If you have any questions or feedback, please don't hesitate to ask us on the Info page or at hello@randomwidgets.com

### 1.2.1 — 2016-07-05

We hope that you enjoy this new update for iCSC! We had a great WWDC16 and learned a lot about how to make iCSC better. If you like iCSC, please rate it or spread the word - everything helps!

This release has some bug fixes and adds the following features:
- Updated Favorites Adding User Interface
- The "Open To Favorites" feature has returned ;)

If you have any issues, please reach out to us at help@randomwidgets.com.

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## More apps by Random Widgets LLC

- [iBehave](https://appshunter.io/ios/app/ibehave/id495667452)

All apps by Random Widgets LLC: https://appshunter.io/developer/1689907576

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-28.*