Comparison

Star Exposure Calculator vs Zenith Annotation

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

Head to head
About

Star Exposure Calculator

Features
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Star Exposure Calculator is an app that helps you calculate the right exposure settings for pin-sharp stars in astrophotography. Features: • Calculate star exposure via simple or complete NPF rule for pin-sharp stars • Calculate star exposure via 500 rule • Calculate focal ratio of your telescope • Telescope magnification calculator • Maximum telescope magnification calculator • Telescope true field of view calculator We constantly update the app to provide more features that users are looking for, so expect even more with future updates.

About

Zenith Annotation

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Study and present your astronomical images on iPhone and iPad. Zenith Annotation brings image import, astrometry, annotations, and presentation tools together in a guided workflow. Explore the field • Open the images you choose from Photos or Files, including TIFF and TIF images. • Solve a field online when you request it and agree to send a working copy. • Browse catalogs and review object and session details. Prepare your annotations • Organize layers, labels, data, and visual styles. • Keep project progress on your device. • Preserve the original file: online solving uses a reduced grayscale copy, not the original. Present your work • Design carousels with editable text, charts, palettes, and animations. • Arrange images and text in collages. • Export a result to save or share yourself. Online solving requires a connection and your explicit action. For this feature, the app sends Astrometry.net a reduced grayscale copy of up to 2048 pixels without EXIF metadata. Zenith Annotation does not transmit the original file or publish your images to social networks. Annotation Studio Choose how to start: try 14 days free if your Apple account is eligible, or pay for the year up front. The plan automatically renews after the trial at the price shown by your App Store; in Mexico, that price is MXN $549 per year. Direct payment charges the displayed annual price at the start. Manage or cancel renewal in your Apple account settings. Purchase restoration is included. Terms of Use (Apple Standard EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

Star Exposure Calculator4 screens
Zenith Annotation3 screens

Verdict

The call

The clearest difference is in-app purchases: Star Exposure Calculator at none against Zenith Annotation's 2. Star Exposure Calculator also leads on iOS requirement (13.0 vs 15.0). Zenith Annotation's advantage is ads (none vs shown). On price, update cadence and device support there is nothing between them.

Scored on Price Ā· Rating Ā· Positive reviews Ā· Number of ratings Ā· Update frequency Ā· Ads Ā· In-app purchases Ā· Monetization Ā· Best chart rank Ā· Devices Ā· Requires iOS

CostPrice Ā· In-app purchases Ā· Ads Ā· Monetization

Both are free to download. Zenith Annotation sells 2 in-app purchases, starting at $24.99 per year. Star Exposure Calculator asks for nothing beyond the download.

UpkeepUpdate frequency

Star Exposure Calculator ships an update every 2 weeks, Zenith Annotation every 10 days. The most recent releases landed on October 30, 2026 and October 31, 2026 respectively.

Scorecard3 real differences Ā· 3 level
Star Exposure Calculator versus Zenith Annotation: the parameters behind the verdict, then further details
ParameterStar Exposure CalculatorZenith Annotation
PriceFreeFree
Update frequencyEvery 2 weeksEvery 10 days — better
AdsYesNo — better
In-app purchasesNo — betterYes
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS13.0 — better15.0
Further details — not scored
Size25 MB47 MB
Age rating4+4+
DeveloperDejan BorasEduardo Martinez Gomez

In-app purchases

None

Star Exposure Calculator

No in-app purchases

2 purchases

Zenith Annotation

Subscriptions2
  • Annotation Studio with Trial14 Days trial$24.991 Year
  • Annotation Studio Annual$24.991 Year

Questions

Is Star Exposure Calculator free?
Star Exposure Calculator is free to download, with no in-app purchases.
Is Zenith Annotation free?
Zenith Annotation is free to download, with in-app purchases available.
Do Star Exposure Calculator or Zenith Annotation have ads?
Star Exposure Calculator shows ads; Zenith Annotation does not.
Which is updated more often, Star Exposure Calculator or Zenith Annotation?
Star Exposure Calculator ships an update every 2 weeks, and Zenith Annotation every 10 days. Most recently, Star Exposure Calculator was updated on October 30, 2026 and Zenith Annotation on October 31, 2026.

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