Comparison

Emerald Chronometer vs SynScan Pro

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

Head to head
About

Emerald Chronometer

Experience highly detailed mechanical watch faces with advanced astronomical and clock complications. Track celestial events, manage time with precision, and explore historical and future dates with interactive displays. Optimized for iPhone and iPod touch.

Highlights
  • Accurate astronomical data (4000 BCE - 2800 CE)
  • Sun, Moon, and planet rise/set times
  • Mechanical display of Moon phases
  • Precise local and UTC time
  • Chronograph with split timer
  • World-time and calendar watches
  • Interactive time-travel simulation
Read full description

These models of high-end mechanical watch faces contain many of the most complex "complications" found in real watches, plus refinements found nowhere else. All displays maintain the look and feel of real mechanical objects, but with the time and location accuracy of the iPhone. NOTE: This app (Emerald Chronometer) is optimized for the iPhone and iPod touch. Please also see Emerald Chronometer HD, a separate product optimized for the iPad. Astronomy features: - Highly accurate data from 4000 BCE to 2800 CE - Times of rise and set for the Sun, the Moon, and the 5 classical planets - The correct shape and orientation of the Moon in all phases but still using a mechanical display - Relative positions of the Sun, Moon, 6 planets and the constellations of the zodiac - "Compass functions" show the elevation and azimuth of the Sun, the Moon, and the 5 planets - The Equation of Time, solar time and sidereal time - Eclipse predictor (lunar node indicators and separation indicator) - User settable geographic location and timezone using an 80,000 city database - A unique face showing the rise and set times of all 5 classical planets plus the Sun and the Moon at once Clock features: - Day/date/month/year indicators, using mechanical wheels - Local and UTC time - Chronograph (stopwatch) with split timer, 1/10 sec accuracy - Alarm clock and interval timer; notifications are delivered in iOS 4 if the app is not running** - World-time watch with 24-city ring on one side and 4 subdials on the other - Calendar watch with rotating wheels showing a full month at a time - Most watches with 1/5 sec or 1/10 sec precision - Synchronized with standard atomic clocks via NTP There are 16 watches in all, with 27 total watch faces (including front and back sides). A setting is available to allow the display to stay on only when plugged in. Play with the watches by tapping on the crown and moving the hands, or press and hold on a date window to zoom through time to see the effect on the heavens. Then just use them to show you when it's time for a break. A complete description of each application feature can be found in the built-in Help screens and on the Emerald Sequoia LLC Web Site, which also includes a demo movie. A developer's blog may also be found at http://emeraldsequoia.com/esblog/ . If you are having any trouble with the application whatsoever, please see our FAQ on the support page listed below and then contact us through that page if your problem is not resolved. We take pride in responding promptly to all support email requests. **NTP accuracy is not guaranteed for alarm delivery if the app is not running. (NTP requires Internet access. Like all apps Emerald Chronometer can not change the device's internal clock.)

About

SynScan Pro

Control motorized telescope mounts for celestial observation and astrophotography. Features include precise slewing, alignment, GOTO, and tracking of stars, planets, and deep-sky objects. Supports advanced functions like polar alignment and camera triggering.

Highlights
  • Control telescope mount (slew, align, GOTO, track)
  • Point and Track celestial objects
  • Gamepad navigation support
  • Catalog of celestial objects
  • Third-party app integration (ASCOM, SkySafari)
  • Polar alignment (with or without polar scope)
  • Camera shutter release control
Features
Read full description

Use the SynScan app to control Sky-Watcher telescope mounts via Wi-Fi or Bluetooth LE. Mounts without built-in Wi-Fi can be supported via a SynScan Wi-Fi adapter. This is the Pro version of the SynScan app and contains features suited for expert users using equatorial mounts. Features - Control telescope mount to slew, align, GOTO and track. - Point And Track: track celestial objects (including the Sun and planets) without aligning. - Support gamepad navigation. - Browse a catalog of stars, comets, and deep sky objects. Or, save your own objects. - Provide access to mount for use by third-party apps, including ASCOM clients, SkySafari, Luminos, Stellarium Mobile Plus, Stellarium Desktop or customer-developed apps. Also set up mount alignment for Luminos, Skysafari. - Support access to the mount and the SynScan app from any platform that supports TCP/UDP connections. - Provide emulator mount for testing and practicing. - Track fast-moving earth satellites by working with the PreviSat app on Windows PC or the Lumios app on iOS devices. - Perform polar alignment with or without a polar scope. - Control shutter release (SNAP) port to trigger an attached camera. (Requires mount with SNAP port and adapter cable that matches camera.) - Use ASCOM to perform autoguiding on mounts that do not have autoguider (ST-4) port. - Other mount controls: auto home, PPEC, park.

Screenshots

Emerald Chronometer4 screens
SynScan Pro4 screens

Verdict

The call

The clearest difference is review sentiment: Emerald Chronometer at 97% against SynScan Pro's 22%. Emerald Chronometer also leads on rating (4.9 vs 2.6). SynScan Pro's advantage is update cadence (every 2 months vs every 22 months). On price, ratings volume, in-app purchases and monetization model 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. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

Emerald Chronometer holds the better App Store score, 4.9 against 2.6. Both are backed by a comparable volume of ratings — 105 and 51 respectively. Written reviews point the same way: 97% of Emerald Chronometer's written reviews are positive against 22% of SynScan Pro's.

UpkeepUpdate frequency

Emerald Chronometer ships an update every 22 months, SynScan Pro every 2 months. The most recent releases landed on October 6, 2026 and October 9, 2026 respectively.

Scorecard3 real differences · 7 level
Emerald Chronometer versus SynScan Pro: the parameters behind the verdict, then further details
ParameterEmerald ChronometerSynScan Pro
PriceFreeFree
Rating4.9 (105 ratings) — better2.6 (51 ratings)
Positive reviews96.8% of reviews — better21.5% of reviews
Number of ratings105 — better51
Update frequencyEvery 22 monthsEvery 2 months — better
Ads—No
In-app purchasesNoNo
MonetizationPaidPaid
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.014.0 — better
Further details — not scored
Size311 MB46 MB
Age rating4+4+
DeveloperScapa Flow, LLCAstropower Technology Co. Ltd.

Customer experience

Emerald Chronometer

All ratings96 ratings
Positive97.9%
Neutral1.0%
Negative1.0%
Written reviews63 reviews
Positive96.8%
Neutral3.2%
Negative0.0%

SynScan Pro

All ratings51 ratings
Positive33.3%
Neutral13.7%
Negative52.9%
Written reviews93 reviews
Positive21.5%
Neutral20.4%
Negative58.1%

In-app purchases

None

Emerald Chronometer

No in-app purchases

None

SynScan Pro

No in-app purchases

Questions

Is Emerald Chronometer free?
Emerald Chronometer is free to download, with no in-app purchases.
Is SynScan Pro free?
SynScan Pro is free to download, with no in-app purchases.
Which has better reviews, Emerald Chronometer or SynScan Pro?
Emerald Chronometer is rated higher. Emerald Chronometer averages 4.9 out of 5 from 105 ratings, while SynScan Pro averages 2.6 from 51 ratings.
Which is updated more often, Emerald Chronometer or SynScan Pro?
Emerald Chronometer ships an update every 22 months, and SynScan Pro every 2 months. Most recently, Emerald Chronometer was updated on October 6, 2026 and SynScan Pro on October 9, 2026.

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