LSTclock: sidereal time clock

Name: LSTclock: sidereal time clock
Rating: 3.8 (10 reviews)
Author: Tsuyoshi Sawada

By: Tsuyoshi Sawada

Local sidereal time clock

Features & Capabilities

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).

User Growth & Download Statistics

App

By:

Tsuyoshi Sawada

Rating:

3.80

(10)

Version:

9.3 Last updated: 2026-03-20

Version code:

882686761

Creation date:

2020-04-26

Compatible devices:

Size:

8.94MB

URLs:

Full description:

Source:

Apple Apps Store

Data ingested on:

2026-07-04

Compare stats and ranking:

Ranking

# 427,581 ▼ 4,443

For Developers

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Contact the developer

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Developed by:

Tsuyoshi Sawada

Apple Apps Store

https://apps.apple.com/us/app/lstclock-sidereal-time-clock/id1510148631

User Reviews

There is much to discover about sidereal time with this app. Take the time to read the user guide to access multiple functions. One suggestion for the developer: a user setting to allow the app to override the lock screen timeout optionally for a constant on display setting. Thank you for bringing this very useful app to the iOS environment.

by RD*****, 2025-12-25

Astronomers often need to use standard and local sidereal time which is done in the app; but more importantly for record keeping, they also need Julian and Modified Julian Dates. The app does not show JD or MJD and really needs to do this to be useful and bumped from three to five stars. Having to go to settings for time (which is not self explanatory) in order to get the JD and MJD is a pain. Just display both under the LST. Hope the developer takes this under advisement. 14 December 2024 UPDATE: Tsuyoshi Sawada quickly responded with a note through the Apple App store that he added an optional setting to switch on or off the JD/MJD in his LSTClock and I tested it this evening when making my observations. It is a perfect solution to a long term issue that I have struggled with in my work having to look things up and compute JD and MJD with online calculators. Tsuyoshi, your solution is perfect! Thank you for responding so quickly and as promised, your app is not rated ⭐️⭐️⭐️⭐️⭐️ and more. Thank you so very much!