Comparison

Emerald Observatory for iPad vs LSTclock

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

Head to head
About

Emerald Observatory for iPad

This app provides a comprehensive astronomical display on a single screen, offering detailed information about celestial bodies and timekeeping. It features a heliocentric orrery, rise and set times, twilight information, and moon phase details. Users can navigate through time and set alarms for astronomical events.

Highlights
  • Astronomical information display
  • Heliocentric orrery
  • Rise and set times for Sun, Moon, planets
  • Twilight times
  • Moon phase and orientation
  • World map of day/night regions
  • Eclipse simulator
Features
Read full description

Emerald Observatory displays a wealth of astronomical information all on one screen, in a unique but understandable format. Information includes: - 12- and 24-hour ordinary clock time - Times of rise and set for the Sun, the Moon, and the 5 classical planets - Times of the beginning and ending of twilight - Heliocentric orrery (display of the planets in orbit around the Sun) - Altitude and azimuth for the same bodies (one body at a time) - Current phase and apparent orientation and relative size of the moon - Current regions of day and night on a world map - The Equation of Time, solar time, UTC time, and sidereal time - Month, day, year, and leap-year indicator - Daily alarm (delivered as local notification on iOS 4+ if app is not running) - Eclipse simulator - Displayed times are synchronized via NTP to "atomic clock" standard - Uses iPad location, or the latitude and longitude may be set manually A setting is available to allow the display to stay on continuously. Tap on the display to move forward by a month, day, year, hour, or minute. A detailed manual for the operation of Emerald Observatory can be found at the "Emerald Sequoia LLC Web Site" listed below, at http://emeraldsequoia.com/eo/ 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 but we can't fix it if you don't report it (and we have no way to respond to Customer Reviews on iTunes). (NTP requires Internet access. Like all apps Emerald Observatory can not change the device's internal clock.)

About

LSTclock

This utility app displays local sidereal time for registered locations on iOS, iPadOS, and watchOS. It can also calculate sidereal time and Julian Date for any date and time, and sync locations between devices.

Highlights
  • Local sidereal time display
  • Julian Date calculation
  • Supports multiple registered locations
  • Location sync between iPhone and Apple Watch
  • Date and time specific calculations
Features
Read full description

LSTclock is an iOS/iPadOS/watchOS app that displays the local sidereal time (LST) at registered location(s). On iOS/iPadOS, it can also calculate LST and Julian Date for any date and time. The list of locations can be synced between iPhone and paired Apple Watch(es).

Screenshots

LSTclock4 screens

Verdict

The call

The clearest difference is review sentiment: Emerald Observatory for iPad at 99% against LSTclock's 55%. Emerald Observatory for iPad also leads on rating (4.9 vs 3.8) and ratings volume (84 vs 10). LSTclock's advantage is monetization model (free vs paid) and update cadence (every 2 months vs every 5 months). On price, ads, in-app purchases and iOS requirement 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 Observatory for iPad holds the better App Store score, 4.9 against 3.8. That said, the two scores are not equally well evidenced: Emerald Observatory for iPad has 84 ratings behind it against 10, so its average is the more settled of the two. Written reviews point the same way: 99% of Emerald Observatory for iPad's written reviews are positive against 55% of LSTclock's.

UpkeepUpdate frequency

Emerald Observatory for iPad ships an update every 5 months, LSTclock every 2 months. The most recent releases landed on September 25, 2026 and September 9, 2026 respectively.

Scorecard6 real differences · 4 level
Emerald Observatory for iPad versus LSTclock: the parameters behind the verdict, then further details
ParameterEmerald Observatory for iPadLSTclock
PriceFreeFree
Rating4.9 (84 ratings) — better3.8 (10 ratings)
Positive reviews98.6% of reviews — better54.5% of reviews
Number of ratings84 — better10
Update frequencyEvery 5 monthsEvery 2 months — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaidFree — better
DevicesiPadiPhone, iPad, Apple Watch — better
Requires iOS17.017.0
Further details — not scored
Size16 MB15 MB
Age rating4+4+
DeveloperBjorn Freeman-BensonTsuyoshi Sawada

Customer experience

Emerald Observatory for iPad

All ratings84 ratings
Positive97.6%
Neutral1.2%
Negative1.2%
Written reviews145 reviews
Positive98.6%
Neutral0.0%
Negative1.4%

LSTclock

All ratings10 ratings
Positive60.0%
Neutral10.0%
Negative30.0%
Written reviews11 reviews
Positive54.5%
Neutral18.2%
Negative27.3%

Bugs and requests

Emerald Observatory for iPad

Requested features

14 requests
  • Port to screen wallpaper
  • Large wall clock version
  • Apple TV version
  • Support for Uranus, Neptune, and Pluto
  • iPhone and Apple Watch versions
Show 9 more
  • Alarm functionality
  • Screen dimming for night use
  • Numeric display of values
  • Switch altitude/azimuth by touching planet
  • Push notifications for specific events
  • Custom chime sounds for events
  • Round earth display to match moon display
  • iPad version of Chronometer iPhone app
  • Tutorial mode or on-screen help

LSTclock

Not enough reviews yet to summarise bugs or requests.

In-app purchases

None

Emerald Observatory for iPad

No in-app purchases

None

LSTclock

No in-app purchases

Questions

Is Emerald Observatory for iPad free?
Emerald Observatory for iPad is free to download, with no in-app purchases.
Is LSTclock free?
LSTclock is free to download, with no in-app purchases.
Which has better reviews, Emerald Observatory for iPad or LSTclock?
Emerald Observatory for iPad is rated higher. Emerald Observatory for iPad averages 4.9 out of 5 from 84 ratings, while LSTclock averages 3.8 from 10 ratings.
Do Emerald Observatory for iPad or LSTclock have ads?
Neither Emerald Observatory for iPad nor LSTclock shows ads.
Which is updated more often, Emerald Observatory for iPad or LSTclock?
Emerald Observatory for iPad ships an update every 5 months, and LSTclock every 2 months. Most recently, Emerald Observatory for iPad was updated on September 25, 2026 and LSTclock on September 9, 2026.

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