iPhone Screenshots


The Sidereal Time App gives the user a simple and quick way to determine:

- Local Apparent Sidereal Time (LAST) based on longitude
- Rough estimate of LAST based on Time Zone
- Greenwich Apparent Sidereal Time (GAST)
- Select one of 30 Stratum-1 NTP servers or add your own to synchronize the clock against the primary network time standard

The App uses core location (GPS, cellular triangulation and/or Skyhook Wireless's Wi-Fi system) to determine the users present position and hence his LAST. The user may also manually select the longitude coordinate to determine LAST or make a rough estimate by selecting a Time Zone.

A running clock with the Coordinated Universal Time is presented in parallel with the Sidereal Time clock.

Local Apparent Sidereal Time at any location differs from the Greenwich Sidereal Time value of the same moment, by an amount that depends on the longitude of the location. When one moves eastward 15° in longitude, sidereal time is larger by one hour and hence wraps around at 24 hours. Unlike computing local solar time, differences in longitude and time are counted here to the accuracy of measurement, not just in whole hours.

What's New

Version 1.7

Updated for iOS 11.0.
Minor bug corrections.

Ratings and Reviews

3.2 out of 5

6 Ratings

6 Ratings

Nice App

The Soul Rider

This seems to be a nice app. Simple, pleasing design, nice colors. But needs an alarm clock for sidereal time and a countdown clock without an alarm.

Unable to set.


I just got this app and I cannot find any settings. I am only getting two clocks one for Greenwich Mean Time and one for Universal with no ability to get my local sidereal time. Am I missing something?

Nice app


Needs an alarm to alert when is your own sidereal time.


Milan Battelino
1.1 MB
Requires iOS 8.0 or later. Compatible with iPhone, iPad, and iPod touch.
Age Rating
Rated 4+
© 2011 CosmoWerx


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