CMOS/WebCams

Typical cheap webcam – CMOS camera

See more with CMOS

There are many different types of cameras for many astrophotography applications. Whether you are doing planetary imaging, deep sky imaging – as with galaxies or nebulae, or just night sky views – such as trying to capture our Milky Way galaxy or star trails, selecting the appropriate camera can be challenging.  Below lists a few examples of some types CMOS cameras and Webcams used in the wild today.

Depending on your webcam, optics, and conditions of your location and the sky, it is possible to obtain pictures of nebulae.

CMOS (Complementary Metal Oxide Semiconductor) sensors differ in terms of their construction.  CCDs (Charge Coupled Devices) collect the charge at each photo-site, and transfer it from the sensor through a light-shielded vertical array of pixels, before it is converted to a signal and amplified.  CMOS sensors convert charge to voltage and amplify the signal at each pixel location, and so output voltage rather than charge.  CMOS sensors may also typically incorporate extra transistors for other functionality, such as noise reduction.

 

The CMOS sensor also has some advantages over CCD:

  • Lower power consumption, on the order of 100 times less than a CCD.
  • CMOS sensors can integrate camera functions like auto exposure, color encoding, and image compression directly in the chip.
  • When an image is overexposed, it can lead to ‘blooming’ around the pixels affected with CCD sensors.  CMOS technology mitigates this effect.
  • Known to be faster at processing images because of an ADC (analog-to-digital converter) and the active pixels and are on the same chip.
  • Technology has advanced with CMOS sensors, from their introduction, as their quality has improved greatly and they have since become the new standard.
Comparison between CCD and CMOS photon to voltage conversion

 While there are many cameras on the market to choose from, there is also an assortment of software to run those cameras.  Fortunately, the more popular the camera, the better software and drivers are written and updated for your particular camera and computer operating system.  On the flip side of the coin, there are also other cameras that are not so popular, which are coming on the scene with less than stellar software and support.

1/2 inch Sony CCD sensor (ICX205AK) 1,280×960 (1.2 MP), up to 15 fps Global shutter Manufactured by The Imaging Source

It’s all in the driver

Some cameras are more of a challenge to get through the initial setup and obtain a first light image.  It all comes down to the drivers for the particular camera and the accompanying image capturing software, should there be software from the maker of the particular brand of camera.  The challenge is finding a driver to match your flavor of operating system, and the model of the camera.  Fortunately, most manufacturers are pretty good about updating drivers and their software.  Those cameras mentioned in this post are the rule and not the exception.

5x Barlow – LX850ACF 10″ f/8 – DFK 41AU02.AS – 50 Images stack – Post processed by Registax

Some drivers are also available via the ASCOM Platform.  This is a standards driven body, made up of a group of developers and astronomical product makers, for delivering vendor and language independent software to the astronomical community.

Once you’ve found your driver and can access the camera from your desktop of choice, then comes the selection of what image capturing software to use.  The Imaging Source, makers of the DFK*, and DMK* product line of cameras, provide excellent support for their imagers.  Their software, known as IC Capture, is a great tool for capturing images of celestial objects.  The Jupiter image above was captured with this software.  As mentioned previously, deep-sky images are also possible, given suitable seeing conditions.

IC Capture allows you to adjust your frame rate for those sky conditions where you need a faster capture to mitigate shuddering of your image resultant from turbulent air.  You can also adjust your gain, exposure, change your hue and saturation, and also record many frames in succession, sent to an .AVI file, which you can split up and stack later in post with stacking software.

Image result for ic capture
IC Capture Software, from The Imaging Source

So many choices, so little money

QHY QHY5III178 USB 3.0 Monochrome CMOS Imaging Camera – QHY5III178M

QHYCCD also manufacturers excellent cameras, such as the QHY5III178M shown below.  These small form factor cameras provide highly quantum efficient sensors while providing low readout noise.  With USB 3.0 capability, these high speed, high frame rate cameras can serve as your planetary imager, or as a guiding camera, or both.  The camera has a guide port to send corrections to your tracking mount.  With the use of SharpCap, or other imaging software tools, taking quality images has never been easier.  With an intuitive interface, along with many options, capturing detailed images is a snap.

This camera, also, can be a deep-sky imager, given even less than ideal seeing conditions.  As for use as a guiding camera, as mentioned this model has a guide port which can send corrections to a tracking mount.  With the use of software, like PHD2, et al, crisp detail and minimal tracking drift is possible to give you excellent images.  These imaging and guiding software tools play nice with each other, for the most part, so running Sharpcap and PHD2 at the same time is quite handy when you want to image with one camera and guide with another.

Image taken with QHYCCD camera

Lastly, at least for this post anyway, I mention the ZWO line of cameras.  These cameras are affordable, and surprisingly excellent imagers for the money.  They are great, as the others mentioned, at planetary and also deep-sky imaging.   These cameras also have excellent support for software and drivers.  They also utilize tools such as Sharpcap and PHD2, as the ZWO product line can be used as an imager and guider.

ZWO-ASI120MC – Digital CMOS Monochrome Camera

The goal of planetary imaging is by making use of the popularity of high-speed CMOS and Webcam video cameras as a utility for astrophotography.  Typically, amateurs make use of a monochrome camera with individual color filters to record several frames that can be saved as a video file, .AVI for example.  They are then post processed by stacking, sharpening, and combining those frames into the final color image.  You can eliminate the monochrome camera if you prefer, which require additional filter wheels and typically expensive filters, and instead use a color video camera to record some of the highest-quality planetary images around.  This is typically done with a debayering post process, after capturing the frames with a raw codec, such as Y800.  Or you can capture in raw debayered mode which will debayer the video frames directly in your camera.  This increases the data size of the frame, typically about threefold.  Perhaps a future post to discuss this in further detail may be prudent.

However you accomplish planetary and deep-sky imaging, using high speed video cameras is definitely one of the more popular ways to achieve your goal.