Until recently the only way to view deep sky objects in real time with the assistance of a camera was with one of the many analog cameras like those from Stellacam, Mallincam, Altair Astro, Samsung and a few others. These security cameras re-purposed for astronomy have very sensitive CCDs which can collect enough light in a few seconds to a few tens of seconds to provide stunning views of a wealth of deep sky objects. Some of these cameras have been modified to provide improved astronomical performance. These may include extended exposure, reduced amp glow, sensor cooling, remote control and more, while other cameras like the Samsungs have no astronomy modifications at all. In either case, they provide the user with many important advantages over the traditional view through an eye piece such as:
Since these are analog cameras, they provide a video signal which can be viewed directly on any video monitor, LCD or television with a video (RCA) input. All that is needed is the appropriate cable and connector. Images can also viewed on a computer if the video signal is connected to the computer through a video capture device like the Pinnacle Dazzle or EzCap. Using a computer has the added advantage of allowing the user to capture images, as well as, utilize fancy software programs to stack frames on the fly, remove hot/warm pixels with dark frame subtraction and perform other miraculous feats to greatly improve the detail in the image being viewed live.
Somewhere around 2009, people discovered that the Starlight Xpress Lodestar guide camera was actually a very good camera for viewing deep sky objects in real time. This camera uses the PAL version of the same very sensitive CCD sensor as the Mallincam Xterminator, the Sony ICX829. While the Xterminator is another analog camera, the Lodestar is a digital camera with a USB output which can be connected directly to a computer without a video capture device. And, unlike the analog cameras which need separate cables for power, signal and control, this digital camera uses the single USB cable for all three functions. On the other hand, since the output is digital it cannot be connected directly to an LCD or other analog display device and needs a computer to control the camera and view its output. The Lodestar is controlled with Paul Shears software, Lodestar Live (now called Starlight Live) which also provides the ability to view, capture, stack and stretch images live while watching them improve in depth and detail. Despite these capabilities, most real time viewers seemed happy to continue to embrace their analog cameras including several newer and better cameras like the aforementioned Mallincam Xterminator, the LnTech300 ( also sold as the Revolution Imager 1) and the Revolution Imager 2.
Then, in 2015 a company in China called ZWO introduced an astronomy camera with a CMOS sensor, the Sony IMX224. Their ASI224, like the Lodestar, is a digital camera but with much higher resolution than the Lodestar and all of the analog cameras while maintaining very good sensitivity. The ASI224 is controlled with a software program called Sharpcap, which has all the same features as Starlight Live and more. Even though the ASI224 has a small sensor, 1/3", it has 1.27 Mega pixels, more than double the Lodestar and all astronomical analog cameras. And, its square 3.75 micron pixels are less than half the size of the typical analog camera pixels which provides more detail and more realistic looking stars, i.e. round instead of square. In addition, the read out noise of the ASI224 is so low as to make it much more practical to perform live stacking of many very short exposures (2 to 5 sec) with a program like Sharpcap. This minimizes the demands on mount alignment and makes it more practical to use Alt-Az mounts for real time deep sky viewing. The relatively inexpensive ASI224 (originally $350) fast became a favorite of many who had been using the analog camera and soon other manufacturers like Mallincam, QHY, Rising Tech, Orange County Telescopes, Altair Astro came up with their own versions of cameras with the Sony IMX224 CMOS sensor.
Within just a few months, two other digital astronomy cameras for real time viewing became available. One is the well regarded camera from Atik named the Infinity. This camera uses the Sony ICX825 CCD sensor with 1.4 Mega pixels which are slightly larger at 6.45 microns than the IMX224. This is also a 2/3" sensor which provides a much larger FOV at 11mm diagonal compared to the ASI224 at 6mm. It comes with the highly acclaimed Infinity software with all of the same great features for live viewing as the Lodestar software. In fact, the Infinity was the first ATIK camera marketed as a "video camera". Even with a substantial price tag of $1000, the Infinity became very popular particularly as it is noted for its ease of use, especially for beginners.
Around the same time StarLight Xpress came out with their own camera using the ICX825 sensor called the Ultrastar which uses the Starlight Live software just like the Lodestar. And it was not long till Mallincam came out with their version of an ICX825 camera called the StarVision. While the Infinity, Ultrastar and StarVision use CCD sensors as opposed to a CMOS sensor like the ASI224, they all are digital cameras with a single USB output. With these cameras widely available in late 2015 or early 2016, one could say that the floodgates were suddenly opened to digital cameras for real time astronomy.
Not to be outdone, ZWO came out with another digital camera in the spring of 2016, the ASI1600 camera utilizing the Panasonic 4/3" CMOS sensor with 16 Mega pixels. This was a quantum leap in field of view compared to the 1/3" IMX224. The ASI1600 came in color, B&W, cooled and uncooled versions. Atik followed with their own version of this sensor called the Horizon. Both cameras have extremely low read noise, making them ideal for stacking of very short exposures. It was not long before Mallincam also came out with a camera, the DSC16, which uses the Panasonic 16Mega pixel sensor. Camera manufacturers try to differentiate themselves from the pack using identical sensors by providing unique mechanical form factors, added internal memory, different methods of cooling and different software. More recently, ZWO (ASI294) and Mallincam (DS10c) have come out with digital cameras for camera assisted viewing using the latest Sony 4/3" format IMX294 sensor. The IMX294 is a CMOS sensor with 11.7 Mega pixels and very good light sensitivity.
Judging from the posts on the Cloudy Nights "EAA Observation and Equipment" forum, digital cameras are now the new norm for camera assisted viewing. This is not to say that analog cameras are long gone, but do not expect new models to be introduced as all of the manufacturers appear to have shifted to digital cameras. Analog cameras will still have their place so long as they are available new or used, but it is clear that the digital wave has taken the forefront.