The Genesis of Diffraction Limited
Doug George is an electrical engineer and amateur astronomer. In the late 1980’s he became weary of the constantly changing characteristics of popular film emulsions, and decided to take a break from astrophotography. This led directly to the visual discovery in 1989 of Comet Skorichenko-George.
Doug’s interest in astrophotography never waned, and he was excited when the first affordable CCD cameras appeared on the market in 1989. The early cameras could certainly eliminate the tedious manual guiding task, but he was much more interested in their imaging potential. Although early sensors were crude, they already had key advantages over film emulsions. Doug selected a PC-Lynx camera as his first instrument, and was pleased by the excellent sensitivity if not the small array and very primitive software. The vendor was not willing to share details of the software interface, which was a disappointment, but he was able to cobble together a way to take sequences of images automatically. When SBIG brought out the far more powerful ST-6 camera he acquired one and started imaging in earnest.
While the SBIG software was a quantum leap forward, it was DOS-based and relatively difficult to use in the field. Fortunately SBIG had fully documented the software interface for the camera. Thus began a period of experimentation with custom imaging software. In particular Doug adapted a graphical user interface he had developed for his Easy Fringe interferogram analysis software to use as a CCD control program.
Around the same time Ajai Sehgal created a PC implementation of Maximum Entropy Deconvolution. The two teamed up, with Ajai providing the MaxEnt code and Doug adapting his experimental imaging software to provide a user interface and the other required processing and file operations. This was released as Hidden Image, a popular CCD imaging processing package in the early 90’s.
By 1993 the original Easy Fringe software had matured into Quick Fringe, which was selling steadily. The decision was made to incorporate Diffraction Limited to continue to develop it and other future products.
The growing popularity of Windows 3.1 was making life difficult for Hidden Image users, as it required a different memory management configuration. More significantly, in 1995 Ajai Sehgal joined Microsoft, making it impossible for him to continue selling Hidden Image. A deal was struck, and Diffraction Limited licensed the MaxEnt code.
Doug George and Garland Sharratt worked together for a year to write MaxIm DL Version 1, which was released in September 1997. It was the first CCD imaging program designed specifically for Windows 95, and it rapidly grew in popularity.
Today Diffraction Limited continues to develop and improve MaxIm DL as their flagship software product. Diffraction also designs and builds other hardware and software systems both for direct sale and for OEM customers.
The Genesis of SBIG
Back in the 60’s and 70’s the US Vela satellites, designed to detect illicit nuclear tests, instead detected gamma ray bursts from space. Further investigation showed that very distant sources were producing brief bursts of extremely powerful gamma ray radiation. At the time these events were a complete mystery; modern theories attribute them to neutron star collisions and the formation of black holes.
Circa 1984-1985 Katz and others observed a series of optical flashes near the Aries/Perseus border, often referred to as the “Perseus Flasher”. One event was photographed. Claims were made that these were an optical counterpart of the gamma ray bursts, dubbed Optical Gamma Ray Emitter, or Ogre.
A small group called the Santa Barbara Astronomy Group (SBAG), working with Brad Schaefer, were skeptical. To validate or invalidate the proposition about the Ogre, observers worked in pairs, monitoring error boxes containing known gamma ray bursts from satellite data waiting for repetition of an event. The conclusion was that most observed events were satellite glints – sunlight reflecting from flat surfaces on Earth-orbiting satellites. Results published in Astrophysical Journal Sept. 1987 “The Perseus Flasher and Satellite Glints.”
To execute this project, the team had to monitor error boxes – areas of the sky about 10 arc-minutes across – all night for as many nights as possible. The big problem was the motion of the sky; inexpensive telescope mounts could not keep on target for more than an hour or two. All of the observers involved were amateur astronomers with day jobs. A device was needed to automatically correct an inexpensive telescope to keep the field in view all night.
One of the SBAG members, Alan Holmes, had experience with the “new” CCD sensor technology in his work at SBRC. He designed the ST-1 (Star Tracker 1) prototype, which was first tested at Michael Barber’s observatory in January 1988. Improved prototypes (ST-2, ST-3) followed. By 1989 the design was refined and became the well-known ST-4 star tracker.
The guider proved to be far better than needed, and in fact was more than sufficient for astrophotography. A partnership was set up (later incorporated), and SBAG became Santa Barbara Instrument Group, or SBIG. The founders were Richard Schwartz, Alan Holmes, Matt Longmire, and Michael Barber.
Naturally CCD technology lends itself to imaging, and SBIG embarked on a long series of new products. Notable innovations include high performance imaging cameras, spectrographs, adaptive optics, and self-guiding filter wheels.
Acquisition of SBIG
In February of 2011, SBIG was purchased by Aplegen, a biotechnology startup. Their product line was a series of gel document readers, which were built using SBIG cameras. Aplegen’s owners decided three years later to sell the business, and ultimately the assets of SBIG were split away and sold to Diffraction Limited in October 2014.
SBIG and Diffraction Limited Today
Diffraction Limited and SBIG operations have been combined at Diffraction’s facility in Ottawa, Canada. The company’s goal is to provide the best scientific imaging hardware and software available today.