Astrograph telescopes are designed explicitly for astrophotography rather than just visual observation. My main imaging scope is a 12-inch Ritchey-Chretien, Carbon Fiber Truss optical tube assembly (OTA) mounted on a Sky-Watcher EQ8-R Pro mount. The truss construction follows the same design initially pioneered in the 1920s for the large 200-inch Hale Telescope on Mount Palomar in Southern California.

Traditional telescopes often use parabolic or spherical mirrors. Ritchey-Chretiens, or RCs for short, use hyperbolic primary and secondary mirrors. This improved design provides a wider, sharper, and better-illuminated image field with fewer imaging irregularities. The open truss design allows the two quartz mirrors (that already suffer almost no thermal expansion) to acclimatize rapidly to ambient temperatures, an important attribute needed to get sharp images. A lightproof cover, called a light shroud, is placed around the truss “tube” to protect against stray light during regular use.

Telescope at dusk.

The Sky-Watcher EQ8-R Pro mount provides a payload capacity of 50 kg (110 lb) and provides a stable platform for the telescope. A solid mount with powerful drive motors provides accurate and consistent tracking of deep-sky objects when imaging. The optical tube assembly (OTA) weighs 24 kg (53 lb) without additional accessories like a power distribution appliance, astrophotography camera, and various camera accessories like filters.

Imaging camera and off-axis guider configuration.
Imaging camera, guide camera in off-axis guider configuration, and focuser motor.

I use the ZWO ASI2600MC Pro CMOS camera as my primary imaging camera. This high-resolution colour camera has a Peltier cooling system that can cool the sensor to sub-zero temperatures to minimize “noise” in the images. I typically image with the sensor cooled to -12 °C. The ZWO ASI120MM Mini serves as my guide camera attached to the “optical image train” in an off-axis guider (OAG) configuration. The OAG configuration means that I do not use a separate guide scope usually attached to the main telescope. The guide camera gets light from the main telescope’s light path through a prism, so an extra guide scope is unnecessary. Guiding is a very specialized process, but I get good results with the guiding software tool called PHD 2.

The motorized observatory buildings at the Pixelskies facility in Spain (my equipment is in Observatory 2, in the middle).

I host my equipment at the Pixelskies remote telescope hosting facility near Castilléjar, Spain. Dave, the owner of the facility, is exceptionally knowledgeable and friendly. He has been an invaluable support to help get everything set up and tuned in. The observatory building protects the equipment from the elements. It has a motorized roof that opens at night when weather conditions are safe. Sensors control the motorized roofs and monitor ambient light levels, humidity, cloudiness, and wind speeds. The imaging computer’s automation software also uses this sensor telemetry to manage running tasks during imaging sequences.

When I started with this hobby in Southern California, I did not have the luxury of fully automating the whole system. Software automated the repetitive guiding and imaging tasks, but the rest was manual back then. However, things have changed over recent years! Dave from Pixelskies introduced me to the Voyager system integration and automation software solution developed by Leonardo Orazi, and I have not looked back! It is simply brilliant! The robust automation software solution autonomously controls and manages all the connected hardware and preprogrammed photography tasks during imaging sequences at night. For example, a basic workflow generally follows these steps:

  • Power up the primary mirror’s cooling fans one hour before astronomical night.
  • Slew the telescope from its parked “sleeping” position to the Northern pole star position.
  • Start cooling the camera sensor before imaging starts.
  • Refine telescope alignment through a process called plate-solving.
  • Slew the telescope to the chosen deep-sky target(s) for the night.
  • Statistically calculate and set the best camera focus position for the target in the frame.
  • Lock onto multiple guide stars and start guiding to guarantee that the telescope moves precisely in sync with the deep-sky target.
  • Run the imaging sequence(s).
  • Respond to changing weather conditions by suspending and resuming operations based on the sensor telemetry.
  • Safely park the telescope.
  • Safely warm up the camera sensor to the ambient temperature.
  • Power down all the hardware.

Ultimately, the imaging software uploads the night’s images to Cloud storage, where I can download them later for processing. This automation technology frees up my time to research, plan for, and write the automation scripts and imaging sequence instructions for the deep-sky objects I want to photograph ahead of time. For example, I created the photo of Messier 42 (M42) (the Orion Nebula) on the front page of this website from 892 images that used 45 Gigabytes of storage on my hard drive. The telescope took the photos over four cloudless nights during New Moon, over New Year. The final image comprises 19.5 hours of camera exposure time. Processing the typical amount of signal data collected like this is complicated and time-consuming, and I have plenty more to learn about this “artful science”. Automating the “signal acquisition” operation allows me to conveniently plan image processing into my busy family and work schedule.

The start of a clear night at the observatory.

Clouds still roll in, and bright moonlight still interferes with imaging, even in Southern Spain; this is true. However, imaging conditions are excellent for much of the year, and I will soon be testing a high-quality filter that might prove helpful in reducing the majority of the Moon’s interference. I’ll post my findings when the time comes.

Clear skies!