Buying Guide for Astronomical Timer Switches

Tired of manually adjusting your outdoor lights every season? An astronomical timer switch can be your set-it-and-forget-it solution. This device uses your location to automatically align your lighting schedule with the changing sunrise and sunset times throughout the year. 

In this buying guide, we’ll cover the key factors to consider when choosing an astronomical timer switch and review some of the top models on the market.

Factors to Consider When Buying an Astronomical Timer

Let’s explore the key features to consider when choosing an astronomical timer switch to ensure it meets your specific needs:

Price and Budget 

Astronomical timer switches vary in price. While you don’t necessarily need to buy the most expensive model, it’s worth investing in a quality switch from a reputable brand. Look for a timer with durable housing, a well-designed interface, and a warranty of at least 1 to 2 years.

Keep in mind that a higher-priced astronomical time switch may offer additional features and benefits that can make it a worthwhile investment in the long run. For example, a model with a higher amperage rating can control more lighting fixtures, while a unit with multiple channels allows you to set different schedules for various zones.

Features and Specifications 

  • Make sure the switch is rated for the electrical load of your lighting circuit. Common options are 120-277V and 15-20A.
  • Some timers can control multiple lighting circuits independently. Single channel is sufficient for most residential uses, but dual channel offers more flexibility.
  • This maintains the time and program settings during power outages. Otherwise, the timer will need to be reset after each outage.
  • The ability to turn lights on or off manually is very useful. Look for a switch that retains the program during override and resumes automatic operation afterward.
  • Higher-end timers can be set by zip code or GPS coordinates for more precise timing. Basic models may just have a few latitude range settings.
  • Makes it much easier to see and adjust settings in low-light conditions.
  • For outdoor installation, look for a switch with a weatherproof case, ideally rated NEMA 3R or better.

Other factors to consider include the ease of installation, programming options (7-day vs 365-day), and the availability of technical support from the manufacturer. Reading customer reviews can also provide valuable insights into the real-world performance and reliability of different models.

Top Astronomical Timer Switches on the Market

There are dozens of astronomical timer switches available, but some of the most popular and highly rated models include:

Intermatic ST01

The Intermatic ST01 is a solid basic timer at a low price point. It lacks some advanced features but is easy to program with up to 7 on/off settings per day. The ST01 is a good choice for controlling a single circuit of landscape lights or other dusk-to-dawn lighting. However, it may not be suitable for more complex applications or harsh outdoor environments.

Intermatic ET90215CR

The Intermatic ET90215CR is a flexible, high-end timer supporting 365-day programming, 2 channels, and automatic Daylight Savings adjustments. It also features a durable NEMA 3R-rated case for reliable outdoor operation. However, it comes at a premium price point that may be overkill for simple applications.

Alion AHC15T

AHC15T Astro Timer
AHC15T Astro Timer

The AHC15T Astro Timer from Alion is a feature-packed astronomical timer switch designed for precision and convenience. With automatic sunrise/sunset control, a perpetual calendar covering 40 years, and power failure memory, this timer ensures reliable, hassle-free operation. Flexible programming options, multiple voltage and frequency selections, and robust switching capacity make it adaptable to various lighting control applications.

Pros and Cons 

The main advantages of astronomical timers are convenience, precision, and energy savings. You don’t have to keep adjusting the on/off times as sunset changes, and your lights will only be on when needed. This can result in significant electricity savings over time, especially for large lighting circuits.

Astronomical timer switches also offer a “set it and forget it” convenience factor. Once programmed, they will operate your lights automatically throughout the year without any need for adjustment. This is especially useful for hard-to-reach locations or for facilities managers responsible for multiple properties.

The main downside is higher costs compared to simple mechanical or digital timers. Astronomical timers can also be more complicated to program, although an intuitive interface makes a big difference. Finally, some lower-quality units may not be durable enough for extreme outdoor conditions or heavy electrical loads.

Choosing the Right Timer for Your Needs

Astronomical Timer Switches for Factory Lighting

For industrial and commercial applications, the most important factors to consider are the electrical ratings, number of channels, and enclosure type. Make sure the timer can handle the total wattage of your lighting loads and is rated for the environment (indoor, outdoor, damp location, etc.).

For complex multi-zone lighting control, you may need a timer with 2, 4, or even 8 channels. However, for the basic dusk-to-dawn operation of area lights, signs, or landscaping, a single-channel astronomical timer is usually sufficient. Look for a model with a high enough amperage rating to control all your fixtures.

Another key consideration for commercial settings is the ease of installation and programming. An astronomical timer switch with clearly labeled wiring terminals and an intuitive interface will save time and frustration for your maintenance staff. A model with remote programming capability may be worth the extra cost in some situations.

For residential use, an affordable single-channel model with battery backup and manual override is a good choice. This will ensure that your lights stay on schedule even during power outages, and allow you to easily turn them on or off as needed without losing your programmed settings.

More advanced features like GPS location or 365-day programming are nice to have but not essential for most homes. However, a timer with dusk/dawn offsets or an adjustable sunset range can be useful for fine-tuning your lighting schedule to your local conditions.

Alion’s Astronomical Timer Switch

AHC15T Astro Timer

Among the various astronomical timer switches available, Alion’s AHC15T stands out for its impressive features, reliability, and user-friendly design. This versatile timer is an excellent choice for both industrial and commercial applications, offering precise sunrise/sunset-based control and a host of convenient functions.

The AHC15T automatically turns lights ON/OFF at the preset sunrise/sunset times based on your location, eliminating the need for manual adjustments throughout the year. With a latitude range of 1-66° for both the northern and southern hemispheres, this timer is suitable for use in most regions worldwide.

One of the key advantages of the AHC15T is its perpetual calendar, which covers a span of 40 years. This feature ensures accurate operation without the need for reprogramming due to date changes. The timer also offers switching preselection and the ability to fully operate without a mains connection, thanks to its built-in lithium battery that maintains settings during power failures.

The AHC15T allows for flexible programming, with options to follow or not follow the sunrise/sunset times. It also features screw terminals for easy installation, an auto-correct time function (within -30 to +30 seconds), and a preset date and time for immediate use. The 12/24 hour format conversion and manual Daylight Saving Time adjustment (1 hour) add to its versatility.

With a compact, self-extinguishing thermoplastic housing and IP20 protection rating, the AHC15T is well-suited for indoor installations. The timer is available in multiple voltage options (AC/DC 12V, AC/DC 24V, AC 110V, or AC 220V) and frequencies (50Hz or 60Hz), accommodating various electrical requirements. The 16A or 20A switching capacity options and 3 or 5 terminal configurations provide additional flexibility for different applications.

The AHC15T is designed to handle a wide range of lighting loads, including filament/halogen lamps, energy-saving lamps, LED lamps, and fluorescent lamps with electronic or conventional ballasts. Its impressive maximum recommended load ratings ensure reliable performance in demanding lighting control applications.

It’s a top-tier choice for those seeking a feature-rich, dependable, and user-friendly astronomical timer switch. With its precise sunrise/sunset control, perpetual calendar, power failure memory, and flexible programming options, the AHC15T is well-equipped to handle a variety of lighting control tasks in both residential and commercial settings. 

With multiple voltage, frequency, and terminal options, along with its robust switching capacity, AHC15T makes it adaptable to diverse electrical requirements. For those looking to upgrade their lighting control system with a high-quality, versatile astronomical timer, the Alion AHC15T is an excellent investment.

Choose Alion’s AHC15T Astro Timer from Alion

With its impressive array of features and rugged construction, Alion’s AHC15T Astro Timer offers an unbeatable combination of performance, reliability, and value for a wide range of lighting control applications. By choosing the AHC15T from Alion, you can enjoy the convenience of automated sunrise/sunset control, energy savings, and reduced maintenance for your lighting system.

By choosing an Alion, you can buy with confidence knowing that you’re getting a top-quality product backed by industry-leading support. Contact us today to know more.



7-Day Heavy-Duty Programmable Timer, 120-277 VAC, 15A, White (1)

Astronomic 365-Day 2-Circuit Electronic Control, 120-277 VAC, 50/60 Hz, 2-SPDT, Outdoor Metal Enclosure, Ethernet Optional (2)


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