Celestron NexImage Burst colour camera
A high-performance CMOS chip sets this Solar System imager apart. See an interactive 360° model of this camera here.
The NexImage Burst is the latest addition to a series of Solar System imaging cameras jointly developed between The Imaging Source (TIS) and Celestron. It is available as either a colour or monochrome camera and uses a 1,280x960-pixel CMOS imaging chip rather than the more traditional CCD chip. We’re reviewing the colour version here, using both Windows 7 and Windows XP laptops for our tests.
When it comes to Solar System imaging, digital cameras are typically used to capture a series of videos, the best frames of which are then processed to create a single still image. This hugely reduces the blurring effects of our atmosphere and produces final images that show significantly more detail than any other method.
To capture the videos in the first place you need a software program that can control the camera. The one supplied with the NexImage Burst is iCap2.3, a generic TIS program capable of running a range of cameras. We found iCap to be rather idiosyncratic, with lots of unused buttons and sliders, greyed-out features and other quirks that could trip up consumers and affect the usability of their recorded videos. It is a pity that with 11 astronomy cameras now jointly produced by TIS and Celestron that they haven’t come up with specifically tailored software. As an alternative to iCap, the camera can also be controlled using the latest beta version of the more user-friendly freeware program FireCapture.
Increasing the frame rate
One significant advantage of this camera over recent offerings from Celestron and TIS is that if you reduce the active area of the chip using the ‘region of interest’ setting you can now also benefit from an increased frame rate as well as the usual reduction in video file size. This is because the region of interest is now set in the camera rather than in the software.
Adjusting the region of interest is useful for smaller targets such as the planets, as gathering more frames generally means more detail in the final image. Through this feature, the frame rate can rise from 25fps at the maximum imaging size of 1,280x960 pixels to a very rapid 197fps at the minimum size of 104x96 pixels.
When focusing using a colour camera it is often helpful to preview the image in colour and you can do this with the dedicated iCap debayer toolbar button – do remember to turn it off before recording though, otherwise your best quality uncompressed (Y800) format video will not be usable. We did pick up an initial issue with the colour sliders having no effect on the colour balance of the Y800 recorded video, but this was fixed by downloading the latest driver from the Celestron website.
We tested the camera, attached to an 8.75-inch Newtonian, on Jupiter as it rose in the east. Correct exposure at medium gain only needed a 10-millisecond exposure, a testament to the high sensitivity of the CMOS chip. Using a region of interest of 464x396 pixels, we achieved a frame rate of 48fps. Noise levels were very low and even allowed a decent image with the gain set to maximum. No odd artefacts were seen on the processed planetary images at this frame rate, which was good news as this has been a problem in other planetary imaging cameras running at similarly high frame rates.
Aiming at the Moon and Sun
Targeting the Moon allowed us to use the whole area of the chip to good effect and produce nice smooth images at 1,280x960 pixels and 25fps. One downside for lunar imaging was the absence of a functional gamma setting in the iCap software, which would have allowed us to accommodate the wide brightness range in some of the higher contrast regions of the lunar surface.
The winter Sun was more of a challenge due to its low altitude, but with a white light solar filter attached to our telescope we again found the camera straightforward to use. We used to the whole chip again to cover a large area of the Sun, picking up details of a large sunspot near the limb as well as faculae and solar granulation. With its 1,280x960 CMOS chip, the NexImage Burst is a simple, well-performing camera that competes with the best digital video cameras on the market. It should enable you to take great images of planets, Sun and Moon.
Low noise, high sensitivity
Unlike the Skyris range of Celestron/TIS cameras, which use CCD chips, the NexImage Burst series possess Aptina ARO132 CMOS chips. CMOS chips used to be the noisier and less-sensitive cousins of CCDs, but recent advances in technology have moved CMOS chips on to the point where noise and sensitivity levels can be comparable or even better. In addition CMOS chips are faster and cheaper than CCDs and run at lower power.
The NexImage Burst’s noise levels, even at maximum gain, were significantly less than those of a Sony 618 chip camera (currently the favoured CCD chip for Solar System imaging) and the sensitivity was slightly better, allowing us to capture more frames in a given time with less noise.
USB connection - The camera possesses a USB 2.0 mini port and is supplied with a 1.2m USB lead, making it compatible with most laptops and computers.
Manual - The eight-page manual is worthy of comment as it is well laid out and clear. It covers system requirements, driver and software installation, together with how to use the camera to capture videos and process them using RegiStax, which is also included on the CD. There are also some useful more general tips on digital video imaging.
Aptina CMOS colour chip - As well as the benefits compared to many CCDs, the 1.2 megapixel CMOS chip in the NexImage Burst allows you to record in colour. Not having to record three separate videos through red, green and blue filters to later produce a colour image – as is the case with monochrome cameras – speeds up the imaging process considerably.
Body - The camera has an attractive and tough-looking circular plastic body with an anodised C-mount metal coupling ring (in trademark Celestron orange) for a 1.25-inch adaptor. And at a very lightweight 29g, this camera is unlikely to upset the balance of your telescope.
1.25-inch adaptor - The 1.25-inch to C-mount adaptor screws onto the front of the camera, allowing you to insert it into an eyepiece holder. The barrel is threaded for filters. Though you won’t need colour filters there are others you might use – such as an infrared-blocking filter, which can improve imaging quality.
This review originally appeared in the March 2015 issue of BBC Sky at Night Magazine.