APT Darkness Clock
APT DC calculates the suitable time for deep sky astrophotography.
App info
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App description
Android App Analysis and Review: APT Darkness Clock, Developed by Distinct Solutions Ltd.. Listed in Tools Category. Current Version Is 2.8, Updated On 28/10/2025 . According to users reviews on Google Play: APT Darkness Clock. Achieved Over 13 thousand Installs. APT Darkness Clock Currently Has 127 Reviews, Average Rating 5.0 Stars
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.astrophotography.app.
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. If the imaging is through narrow band filters, the Moon is less significant factor and important is the time between the astro twilights. This time is named NB Time - Narrow Band Time.
The purpose of APT DC is to calculate what is the DSD / NB Time duration and when these times 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
We are currently offering version 2.8. This is our latest, most optimized version. It is suitable for many different devices. Free download directly apk from the Google Play Store or other versions we're hosting. Moreover, you can download without registration and no login required.
We have more than 2000+ available devices for Samsung, Xiaomi, Huawei, Oppo, Vivo, Motorola, LG, Google, OnePlus, Sony, Tablet ... with so many options, it’s easy for you to choose games or software that fit your device.
It can come in handy if there are any country restrictions or any restrictions from the side of your device on the Google App Store.
What's New
Google Play compatibility update

Recent Comments
Jan Černý
Simple but useful.
Pete F.
Just changed my rating to 5 stars! Developer quickly fixed an issue I was having using the app. It will remain my go-to app for keeping tabs on Deep Sky Darkness time, and planning my future scope outings! This has become one of my most used astronomy apps! I just donated 5 Euros to you guys via. Paypal for being so awesome!
A Google user
Great for a quick appraisal the effect the phase of the moon has on an imaging session. Add a dash of common sense to decide whether to lug the equipment out of the shed.
Niall Thoresen
Great product. Helps establish correct time for my imaging sessions. Works well. Easily detects my location and time zone.
Jeff Hall
Really condenses the stuff I was looking for before in other programs...twilight end, to moon rise for broadband, NB option...everything in one quick glance. Great! Thanks for this app!
Wayne Williams
A good app for me when checking on sunset and sunrise times when doing Astrophotography.
A Google user
Very nice, simple and intuitive .. and no ads!
Luke Yeldham
Love APT well made app thanks