Comparison

CosmoCalc vs Space Telescope App

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

CosmoCalc

This app calculates astronomical distances and scales based on user-selected cosmological parameters. It offers a simple interface for astronomers, students, and enthusiasts to quickly determine various cosmic measurements.

Highlights
  • Select cosmological parameters (H0, Ωm, ΩΛ)
  • Choose from common reference cosmologies
  • Calculate luminosity distance
  • Determine angular diameter distance
  • Calculate lookback time
  • Find age of the Universe
  • Compute comoving volume and critical density
Features
Read full description

CosmoCalc is a simple cosmological distance calculator. With a simple and intuitive interface you can quickly set a reference cosmology and redshift, and CosmoCalc will calculate a full suite of astronomical distances and scales. CosmoCalc is a useful and educational reference tool for astronomers, astronomy students, and anybody interested in calculating the distance to astronomical sources. CosmoCalc allows you to: * Select cosmological parameters H_0, Ω_m, and Ω_Λ with simple touch-screen controls * Easily choose from common reference cosmologies, including Planck 2013, WMAP9, Concordance, and Einstein-deSitter * Quickly determine the luminosity distance, angular diameter distance, lookback time, age of the Universe, comoving volume, and critical density * Easily switch between flat and non-flat cosmologies by clicking on the chain

About

Space Telescope App

Explore the universe with real-time updates and stunning visuals from NASA's James Webb Space Telescope. Engage with expert insights, join community discussions, and test your knowledge with interactive quizzes. Discover distant galaxies and unlock the secrets of the early universe.

Highlights
  • Live mission updates
  • Breathtaking image gallery
  • Expert Q&A with astronomers
  • Community discussions
  • Interactive space quizzes
  • 3D solar system explorer
  • Exclusive wallpapers
Features
Read full description

Space Telescope is an astronomy app for people who actually go outside and look up. See what the James Webb Space Telescope is observing right now. Decide whether tonight is worth staying out for. Catch the next visible ISS pass over your own location, and follow the rocket launches coming up. WHAT WEBB IS LOOKING AT, RIGHT NOW Webb's current target, science category, proposal, instruments and scheduled times, refreshed every five minutes while the view is open. Tap through to the proposal or the full observation schedule. A REAL PLAN FOR METEOR NIGHT Most meteor apps hand you a peak date. This one tells you what you will actually see. Set your location and how dark your sky is, and get an honest meteors-per-hour range, the best viewing window, where to look, how much the Moon will wash out, and what 30, 60 or 90 minutes outside is likely to be worth. Two alerts that matter: a heads-up the evening before, and a nudge when your window opens. Cloud cover is not included, so check the weather before you commit. THE ISS, OVER YOUR HOUSE Live position, altitude, velocity and orbit, plus crew, expeditions, dockings and visiting vehicles. Seven days of passes for your location with quality, direction, peak elevation and duration - set a 10-minute alert or drop the pass straight into your calendar. LAUNCH DAY Upcoming launches with live countdowns, status, provider, rocket, pad, launch window and webcast link. One tap for a reminder 15 minutes before liftoff. GALLERIES WORTH SCROLLING Imagery and mission guides for James Webb, Hubble, Chandra, the Nancy Grace Roman Space Telescope, Artemis, Mars and the ISS. Follow Roman's countdown, instruments and journey to L2. Pinch to zoom, save, share, like and comment. Turn on alerts only for the galleries you care about. PICTURE OF THE DAY NASA's Astronomy Picture of the Day, image or video, with the full expert explanation and an optional daily alert. AND WHEN YOU WANT MORE - Tonight Sky: sunrise, sunset, Moon phase, illumination and twilight - Space Weather: Kp index, solar wind, aurora probability and active alerts - Cosmic Calendar: meteor showers, eclipses and other sky events - Exoplanets: discovery method and year, distance, orbit, mass, radius, temperature, host star and habitable-zone marker - Community astrophotography: post your own shots with gear and conditions - Space wallpapers for your phone - Quizzes, points, levels and global leaderboards - Ask an Astronomer, and live chat rooms in 10 languages - Full interface in English and Spanish PREMIUM Space Telescope is free, with ads. Premium removes every ad, unlocks the premium wallpaper collection and adds a gold avatar ring. Choose a monthly or annual subscription, or pay once for lifetime access, which also grants 1,000,000 points and Diamond level straight away. Subscriptions are charged to your Apple Account and renew automatically unless auto-renew is turned off at least 24 hours before the current period ends. Manage or cancel in your Apple Account settings. Whether you follow Webb every day, plan a Perseids or Geminids watch, photograph the night sky, teach astronomy, or just want to know when the ISS will cross overhead, Space Telescope keeps the useful details in one place. Space Telescope is an independent astronomy app and is not affiliated with or endorsed by NASA, ESA, STScI, SpaceX or any launch provider. Data and imagery are credited to their respective sources. Privacy policy: https://jameswebbtracker.com/privacy-policy Terms of use (Apple standard EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

CosmoCalc3 screens
Space Telescope App4 screens

Verdict

The call

The clearest difference is review sentiment: CosmoCalc at 100% against Space Telescope App's 40%. CosmoCalc also leads on rating (5.0 vs 4.0) and in-app purchases (none vs 4). Space Telescope App's advantage is update cadence (every 10 days vs every 6 months) and ratings volume (30 vs 4). On price 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

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Space Telescope App sells 4 in-app purchases, starting at $4.99 per month. CosmoCalc asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

CosmoCalc holds the better App Store score, 5.0 against 4.0. That said, the two scores are not equally well evidenced: Space Telescope App has 30 ratings behind it against 4, so its average is the more settled of the two. Written reviews point the same way: 100% of CosmoCalc's written reviews are positive against 40% of Space Telescope App's.

UpkeepUpdate frequency

CosmoCalc ships an update every 6 months, Space Telescope App every 10 days. The most recent releases landed on October 6, 2026 and October 7, 2026 respectively.

Scorecard8 real differences · 2 level
CosmoCalc versus Space Telescope App: the parameters behind the verdict, then further details
ParameterCosmoCalcSpace Telescope App
PriceFreeFree
Rating5.0 (4 ratings) — better4.0 (30 ratings)
Positive reviews100.0% of reviews — better40.0% of reviews
Number of ratings430 — better
Update frequencyEvery 6 monthsEvery 10 days — better
AdsNo — betterYes
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS9.0 — better15.0
Further details — not scored
Size1 MB104 MB
Age rating4+4+
DeveloperEli RykoffKAKHA GIORGASHVILI

Customer experience

CosmoCalc

All ratings4 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews5 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Space Telescope App

All ratings30 ratings
Positive73.3%
Neutral6.7%
Negative20.0%
Written reviews30 reviews
Positive40.0%
Neutral10.0%
Negative50.0%

In-app purchases

None

CosmoCalc

No in-app purchases

4 purchases

Space Telescope App

Subscriptions2
  • Monthly Ad-Free Plan$4.991 Month
  • Ad-Free Annual Access$29.991 Year
One-time2
  • Premium$2.99
  • Buy 1M Points$99.99

Questions

Is CosmoCalc free?
CosmoCalc is free to download, with no in-app purchases.
Is Space Telescope App free?
Space Telescope App is free to download, with in-app purchases available.
Which has better reviews, CosmoCalc or Space Telescope App?
CosmoCalc is rated higher. CosmoCalc averages 5.0 out of 5 from 4 ratings, while Space Telescope App averages 4.0 from 30 ratings.
Do CosmoCalc or Space Telescope App have ads?
Space Telescope App shows ads; CosmoCalc does not.
Which is updated more often, CosmoCalc or Space Telescope App?
CosmoCalc ships an update every 6 months, and Space Telescope App every 10 days. Most recently, CosmoCalc was updated on October 6, 2026 and Space Telescope App on October 7, 2026.

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