SQM Mobile vs GuideWatch
Price, ratings, monetisation and update history for both apps, side by side โ with what reviewers say about each.
SQM Mobile
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Bring all your sky quality measurements together in one place. SQM Mobile is the ideal companion for handheld Sky Quality Meters, automatically synchronizing field measurements with SQM Toolbox on your Mac. It also imports measurements exported from Dark Sky Meter Pro, making it easy to build a single long-term archive of all your observations. KEY FEATURES Field-Ready Data Collection * Quick and easy measurement entry for handheld SQM devices * Manual entry of measurements from Dark Sky Meter * Automatic GPS location recording for each measurement * Timestamp for accurate astronomical correlation * Offline measurement storage โ sync whenever a connection becomes available * Bubble level for accurate zenith pointing * Import measurements exported from Dark Sky Meter Pro Smart Location Features * Automatic GPS coordinate capture * Manual location override (to define local sky-background conditions during site surveys) * Perfect for camping trips, dark-sky site surveys and travel observations Automatic Cloud Sync * Seamlessly sync measurements to SQM Toolbox on your Mac via iCloud * Private, secure storage โ only you can access your measurements * Works anywhere with an internet connection โ no complex setup required * Real-time synchronization across all your Apple devices Quick Analysis * Instant Bortle classification for every measurement * On-device light pollution assessment * Comparison with natural sky-background brightness * Simple graphical display including twilight conditions * Measurement validation and quality indicators * Clean, intuitive interface designed for field use Astronomical Context * Automatic twilight condition detection * Moon phase information for every measurement * Sun elevation calculations Simple and Reliable * Designed for easy use in the dark * Large, clear controls for nighttime operation * No account setup required โ simply use your existing iCloud account Perfect for * Amateur astronomers and citizen scientists carrying out site surveys * Researchers monitoring light pollution * Dark-sky organizations documenting observing conditions * Anyone using handheld SQM instruments or Dark Sky Meter who wants long-term storage, synchronization and analysis of their measurements Requires: iOS 17.0 or later, iCloud account Works with: Unihedron Sky Quality Meter (SQM, SQM-L), Dark Sky Meter Pro imports, and manual entry from Dark Sky Meter. Companion to: SQM Toolbox for macOS (available separately)
GuideWatch
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GuideWatch puts your PHD2 guiding session on your wrist. If you run NINA to control your astrophotography rig, you already know the drag of walking back to the laptop every few minutes just to check whether guiding is still holding steady. GuideWatch connects directly to either PHD2 or NINA over your local Wi-Fi network and shows you what matters, right on your Apple Watch: โข Live guiding graph: see RA/Dec error trends update in real time, just like the graph in PHD2 itself โข RMS error and key guiding stats at a glance, with optional haptic alerts if guiding fails โข Simple connection status, so you know instantly if guiding has dropped out โข A quick settings screen to connect to PHD2 or NINA on your controller's IP address and port No need to keep walking back to a screen, break your dark adaptation, or leave a laptop running somewhere inconvenient (just glance at your wrist). GuideWatch also includes a simulation mode, so you can explore the app and its guiding display before connecting it to a live session. Requirements: GuideWatch needs either PHD2 or a NINA instance with the Advanced API module running on the same local network. GuideWatch does not control PHD2, NINA or your imaging session; it's a read-only guiding monitor designed to keep you informed without needing to touch your imaging laptop.
Screenshots
Verdict
The clearest difference is iOS requirement: SQM Mobile at 17.6 against GuideWatch's 26.5. On price, update cadence, ads and in-app purchases there is nothing between them.
Scored on Price ยท Rating ยท Positive reviews ยท Number of ratings ยท Update frequency ยท Ads ยท In-app purchases ยท Monetization ยท Best chart rank ยท Devices ยท Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
SQM Mobile ships an update every 4 weeks, GuideWatch fortnightly. The most recent releases landed on November 5, 2026 and November 6, 2026 respectively.
| Parameter | SQM Mobile | GuideWatch |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 4 weeks | Fortnightly โ better |
| Ads | No | No |
| In-app purchases | No | No |
| Devices | iPhone | iPhone, Apple Watch โ better |
| Requires iOS | 17.6 โ better | 26.5 |
| Further details โ not scored | ||
| Size | 42 MB | 4 MB |
| Age rating | 4+ | 4+ |
| Developer | GerSpatial | Cambridge AI Works Ltd. |
In-app purchases
SQM Mobile
No in-app purchases
GuideWatch
No in-app purchases







