AstroFITS vs Zenith Annotation
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
AstroFITS
This app allows users to quickly open and view FITS files on iOS devices using GPU acceleration. It features automatic image stretching and supports various color formats and bit depths, making astronomical image analysis more accessible.
- Open FITS files quickly on iOS
- GPU accelerated image processing
- Automatic image stretching
- Supports RGB and gray color
- Handles multiple BITPIX formats
- Save adjusted images to Photos
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A simple app to open FITS file in iOS quickly using GPU. It has an auto-stretch feature. And works on FITS file with RGB or gray color. It handles BITPIX of 8,16,32,-32 and -64. It is designed and tested for Seetar FITS file. It takes about 2 seconds to open and automatically stretch a 50mb FITS file. Sample links are provided below. Enjoy! Use: 1. Download your FITS file to your phone File directory. 2. Tap Image icon on the first top left. 3. Select your FITS file. 4. It will auto stretch. 5. Adjust the image level. 6. Adjust the image curve. 7. Tap the second top icon to save image to Photo. If you encounter an issue, please email to ustrainsit74@gmail.com with your FITS file as attachment. Sample: Below are some FITS files for download. - https://drive.google.com/file/d/1Li8f1QH1u1R6U8RKZZ0kwW9LZ4cHCaXz/view?usp=share_link - https://drive.google.com/file/d/1MVuW1oa7qAjbfdl_iGUI-q7knE2ij67v/view?usp=share_link - https://drive.google.com/file/d/1TE70gdDK3XmLx9-iB43I-uh6INq8FCaO/view?usp=share_link Privacy policy and term of use (EULA) is at https://deepskycolor.blogspot.com/2018/12/privacy-policy-for-deep-sky-color-app.html
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
Verdict
The clearest difference is update cadence: Zenith Annotation at daily against AstroFITS's monthly. Zenith Annotation also leads on iOS requirement (15.0 vs 17.0). 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. AstroFITS sells 1 in-app purchase, starting at $0.99 per year and Zenith Annotation sells 2 in-app purchases, starting at $24.99 per year. Whichever you choose, the download price is not the number that matters.
AstroFITS ships an update monthly, Zenith Annotation daily. The most recent releases landed on October 8, 2026 and October 6, 2026 respectively.
| Parameter | AstroFITS | Zenith Annotation |
|---|---|---|
| Price | Free | Free |
| Rating | 2.0 (1 ratings) — better | — |
| Number of ratings | 1 — better | — |
| Update frequency | Monthly | Daily — better |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | Free with in-app purchases | — |
| Devices | iPhone, iPad | iPhone, iPad, iPod — better |
| Requires iOS | 17.0 | 15.0 — better |
| Further details — not scored | ||
| Size | 61 MB | 47 MB |
| Age rating | 4+ | 4+ |
| Developer | yong chong loh | Eduardo Martinez Gomez |
In-app purchases
AstroFITS
- Yearly Subscription$0.991 Year
Zenith Annotation
- Annotation Studio with Trial14 Days trial$24.991 Year
- Annotation Studio Annual$24.991 Year









