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APM Professional Telescopes

APM Professional Telescopes

1m F/8 Ritchey Chrétien with dual Nasmyth Foci, Cape Town (South Africa)

Another large telescope for the South African Astronomical Observatory (SAAO). An 1m F/8 Alt-Az mounted Ritchey Chrétien for robotic use. It has dual Nasmyth Foci. The main telescopes used for research are located at the SAAO observing station (32°22.795’S 20°48,657’E) near Sutherland in the Northern Cape, a 4-hour drive from Cape Town.

ASA Telescopes

ASA600 with DDM200

ASA600 OTA is the perfect fit for the ASA direct drive mounts with absolute encoders. As all ASA telescopes the ASA600 is equipped with quartz glass optics from ASA.


Astroshell Dome 4.25 m

Astroshell Dome 4.25m

CLAMSHELL DOMES provide an unparalleled 360/180 degree field of view for an absolutely breathtaking nighttime experience. When this observatory dome opens, you are truly among the stars!


Product enquiries

Inquiry now

Please make your enquiries about the products you require here. We will contact you as soon as possible with a customised quote.

Sirius Domes

Sirius Observatories Australia has learned that success and innovation comes from overcoming difficulties as a team and with Joe at the helm, we believe that nothing can stand in our way of eventually becoming the number one manufacturer of fiberglass observatories in the world.


SBIG Cloud Sensor

Boltwood Cloud Sensor III


Boltwood Cloud Sensor III

Boltwood II PLus 1Make the most of clear skies.

The newly-designed Boltwood Cloud Sensor III is the must-have observing conditions monitoring device for astronomical observatories. The Boltwood Cloud Sensor III can you alert you to clear conditions, so you can start your observing session.  It also helps protect against observatory equipment damage with warning of clouds, rain, winds, and other unsafe conditions – and can even trigger automatic observatory shutdown.  Coupled with your favorite observatory control application software, the Boltwood Cloud Sensor III enables automated observation scheduling.

Boltwood Cloud Sensor III utilizes Wi-Fi technology for wireless conditions monitoring from up to five computers.  It supports both ASCOM Wi Fi B W 200x164Alpaca interfaces and browser-based monitoring, providing compatibility with any operating system.  Both network operation and Wi-Fi hotspot modes are available.  For Windows users our Clarity III software is also available, providing extra setup and data logging features.

Optional Wired Version

The Boltwood Cloud Sensor III is also available with an optional wired interface version (BOLTWOOD-III-S), which has an RS-232 serial interface and also supports Wi-Fi operation.  A 100′ (30 m) serial cable is included.

For situations where radio-quiet operation is required, a serial-only version is available (BOLTWOOD-III-SO).  This version uses the same hardware but has the Wi-Fi transmitter permanently disabled. A 100′ (30 m) serial cable is included.

For serial interface operation, an ASCOM driver is available for operating the sensor under Microsoft Windows. The serial protocol is also documented in the user manual to facilitate custom software solutions.  Note that this ASCOM driver is not compatible with Wi-Fi operation, which does not require a driver as it uses a direct Alpaca network connection to the sensor.

Download product Data Sheet

 Power Cable
  1. US
  2. European
  3. Australia


  1. WiFi Interface
  2. WiFi and Serial
  3. Serial Only


Boltwood Cloud Sensor III from Diffraction Limited on Vimeo.

Powerful Sensor Technology
The primary sensors used for determining safe/unsafe observing conditions are cloud detection, rain detection, wind speed limits, and daylight. The user can also set limits on other parameters, including humidity, temperature, etc.

The Boltwood Cloud Sensor III will trigger a contact closure (relay) output when it detects adverse conditions. When connected to an observatory roof controller such as the MaxDome II system, this will cause the observatory to close. Note that this will not park your telescope or other equipment.

The Perfect Software
Many users use software to operate the observatory in response to the weather conditions. Diffraction Limited makes Cyanogen Imaging® MaxIm DLTM software, that includes a flexible observatory shutdown capability.

Connect Anywhere

The Boltwood III can operate as a WiFi hotspot or connect directly to your wireless network. There are three different connectivity options available:

  • The Boltwood III connects via standard WiFi connectivity for multiple clients.
  • The Boltwood III-S includes WiFi connectivity and RS-232 serial ports, providing a dedicated hard-wired connection.
  • The Boltwood III-SO connects only the RS-232 serial port, which is more appropriate for more secure environments or where 2.4GHz WiFi radio signals are not desirable. All RS-232 Serial versions include a 50-foot (~15m) serial cable.

Powered. Always.
The sensor operates from a 10.5V to 24V DC power source, making it compatible with 12V solar-charged battery systems. A universal AC adapter and extension cable comes standard to connect with available central power locations.

The sensor detects:

  • Clouds
  • Rain Drops
  • Wet snow
  • Wind Speed
  • Temperature
  • Humidity
  • Dew Point
  • Barometric Pressure
  • Daylight
  • Input Voltage


Approximate Dimensions:
Body 7.5” tall x 4” diameter (190 mm x 100 mm)
Optional Anti-Bird Wires add 1” (25 mm) Mounting Bracket 2.5” from center axis (65 mm)
DC Input Power: 10.5VDC to 24VDC, 1A Maximum
AC Adapter: 100VAC to 250VAC, 50/60 Hz
Power Connector: Barrel style, 2.5 mm ID, 5.5 mm OD, unpolarized Example: DigiKey CP3-1001-ND
Roof Close Connector: Barrel style, 1.3 mm ID, 3.5 mm OD, unpolarized Example: DigiKey EP505B-ND
Roof Close Circuit Rating: 12V, 1A
WiFi Communications: IEEE802.11b/g/n
Center Frequency Range: 2412 ~ 2484 MHz
Country Policy: Automatic configuration based on network station



User Manual

User’s manual for installing and operating the Boltwood Cloud Sensor III



Clarity III for Windows (x86/x64)

Utility for managing your Boltwood Cloud Sensor III and logging data – Production Release 1.0

Download (64-bit) Download (32-bit)

Firmware Update

Firmware version 12 for Boltwood Cloud Sensor III

Click here for release notes.


ASCOM Drivers for Boltwood CSIII Serial Models

Note: This installer is for BCSIII units with a serial port only. WiFi only units make use of the onboard Alpaca REST server to interact via ASCOM.

Download (Win)

Comparative Charts

All the reasons to upgrade to the new and improved Boltwood III Cloud Sensor

Feature / FunctionBoltwood II (Legacy)Boltwood III (New & Improved)
Inclement Weather Protection for Observatory Equipment
Clear Sky & Safe Weather Monitoring
Compatible with Common Astronomy Automation Software
Infrared Sky Temperature Sensor
Ambient Temperature Sensor
Humidity Sensor
Rain Drop Detection
Wind Detection
Daylight Detection
Hardware Signal for Roof & Dome Closure
Clarity Desktop Software for Windows
Boltwood One-Line Weather File Compatibility
WiFi Access X
Wireless Connection X
Multi-User Functionality X
Barometric Pressure Sensor X
ASCOM Alpaca Observing Conditions X
ASCOM Alpaca Safety Monitor X
Built-in Mini Web Server X
Smartphone & Browser Weather Status X
12-Volt Operation for Optional Battery & Solar Power X
Voltage Monitoring: Power Supply Voltage & Battery Report X

APM Professional Telescopes

1m F/8 Ritchey Chrétien with dual Nasmyth Foci, Cape Town (South Africa)

Another large telescope for the South African Astronomical Observatory (SAAO). An 1m F/8 Alt-Az mounted Ritchey Chrétien for robotic use. It has dual Nasmyth Foci. The main telescopes used for research are located at the SAAO observing station (32°22.795’S 20°48,657’E) near Sutherland in the Northern Cape, a 4-hour drive from Cape Town.

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APM Telescopes
Quierschieder Weg 38
66280 Sulzbach

Telefon: +49 (0)6897 - 924929-0
Fax:       +49 (0)6897 - 924929-9
E-Mail: info@apm-telescopes.de
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