Astrolabe Clock vs APT Darkness Clock
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Astrolabe Clock
This app offers a modern interpretation of an ancient astronomical instrument, providing a real-time view of the sky. It displays the time of day, day of the year, and the positions of celestial bodies like the Sun, Moon, planets, and stars. Users can also track sunrise/sunset times, moon phases, and celestial transits.
- Real-time sky view
- Time of day and day of year display
- Sun, Moon, planet, and star locations
- Sunrise and sunset times
- Moon phase tracking
- Celestial transit times
- Eclipse occurrence indicator
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Astrolabe Clock is an astronomical clock inspired by the astrolabe, an ancient astronomical instrument used to tell time and to predict the location of the Sun, stars and planets. This modern interpretation gives a view of the sky showing at a glance the time of day, day of year, and the location in the sky of the Sun, Moon, planets and stars. Astrolabe Clock also gives the time of sunrise and sunset, the phase of the Moon, transit times for the Sun, Moon, planets and stars, and can be used to show the occurrence of solar and lunar eclipses.
APT Darkness Clock
This app calculates the optimal times for deep sky astrophotography and observation based on your location and night sky conditions. It determines the duration and start/end times of ideal darkness, excluding twilight and moonlight.
- Calculates Deep Sky Darkness Time (DSD Time)
- Determines start and end times for DSD Time
- Calculates DSD Time duration
- Supports current location
- Allows storing up to three observing sites
- Free and ad-free
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APT Darkness Clock (APT DC) is a free app without ads, that calculates the suitable time for deep sky astrophotography or observing in selected night and location. It is a small sub-set of a full featured desktop application named APT - Astro Photography Tool. APT is like Swiss army knife for your astro imaging sessions. No matter what are imaging with - Canon EOS, Nikon, CCD or CMOS astro camera, APT has the right tool for planning, collimating, aligning, focusing, framing, plate-solving, controlling, imaging, synchronizing, scheduling, analyzing, monitoring and more. You can find additional information about APT at www.astroplace.net. To image or observe a faint deep sky objects is needed to use the darkest time of the night. This is the time between the evening astro twilight end, the morning astro twilight beginning and when the Moon is below the horizon. In APT that time is named DSD Time - Deep Sky Darkness Time. The purpose of APT DC is to calculate what is the DSD Time duration and when this time starts/ends for selected night and location. It is possible to use the current location or one of three other stored observing sites. For suggestions and support related to APT DC, use the dedicated section of the APT Forum at - http://aptforum.com/phpbb/viewforum.php?f=26
Screenshots
Verdict
The clearest difference is rating: APT Darkness Clock at 5.0 against Astrolabe Clock's 4.7. APT Darkness Clock also leads on update cadence (every 11 days vs every 4 weeks) and review sentiment (100% vs 91%). Astrolabe Clock's advantage is ratings volume (48 vs 4). On price, ads, 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
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
APT Darkness Clock holds the better App Store score, 5.0 against 4.7. That said, the two scores are not equally well evidenced: Astrolabe Clock has 48 ratings behind it against 4, so its average is the more settled of the two. Written reviews point the same way: 91% of Astrolabe Clock's written reviews are positive against 100% of APT Darkness Clock's.
Astrolabe Clock ships an update every 4 weeks, APT Darkness Clock every 11 days. The most recent releases landed on September 15, 2026 and September 8, 2026 respectively.
| Parameter | Astrolabe Clock | APT Darkness Clock |
|---|---|---|
| Price | Free | Free |
| Rating | 4.7 (48 ratings) | 5.0 (4 ratings) — better |
| Positive reviews | 90.9% of reviews | 100.0% of reviews — better |
| Number of ratings | 48 — better | 4 |
| Update frequency | Every 4 weeks | Every 11 days — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 15.6 | 10.0 — better |
| Further details — not scored | ||
| Size | 3 MB | 1 MB |
| Age rating | 4+ | 4+ |
| Developer | Michael Smith | Ivaylo Stoynov |
Customer experience
Astrolabe Clock
APT Darkness Clock
In-app purchases
Astrolabe Clock
No in-app purchases
APT Darkness Clock
No in-app purchases
Questions
Is Astrolabe Clock free?
Is APT Darkness Clock free?
Which has better reviews, Astrolabe Clock or APT Darkness Clock?
Do Astrolabe Clock or APT Darkness Clock have ads?
Which is updated more often, Astrolabe Clock or APT Darkness Clock?
Other comparisons
