Celestron NexImage Solar System Imager
The Celestron NexImage uses the same image sensor as the Philips Toucam range of PC webcams – probably the most popular PC webcam to adapt for astro imaging. The camera has a black plastic case with a threaded 1.25-inch eyepiece adaptor and a USB cable.
We noticed that the 1.25-inch adaptor was a little on the small side, with an actual diameter of just 1.22 inches. It’s not the end of the world but it’s worth making sure that the camera is properly secured in the eyepiece holder. Its long (2.13m) USB cable is slightly unusual in that it’s permanently attached to the camera. While this means you don’t have to hunt around for it in the dark, it also means that if you damage the cable you won’t be able to use the camera.
Installing the NexImage was fairly straightforward: just a case of inserting the supplied CD-ROM into your PC drive and navigating through the self-explanatory selection menu that pops up (accompanied by background music). The software supplied with the camera includes AMCap for control and Registax for post-capture image processing.
The AMCap software is based on a video capture application supplied with the Microsoft DirectX software development kit, modified for final distribution. It works, but some of it isn’t particularly well suited to astro imaging. For example, you nominate a specific file to store your video capture file in, but must nominate a new file for each new capture or your previous one will be overwritten – without warning!
On the plus side, AMCap provides all of the setting adjustments you need for Solar System imaging, like frame rate, exposure and gain. You can also select preset white balance settings or simply go with auto. We found auto worked well, especially if the signal strength was good. Despite offering frame rates of up to 30 frames per second (fps), Celestron recommends sticking at 5fps to avoid the image compression the camera applies at higher frame rates. This is to accommodate the slow USB 1.1 connection.
There’s reasonable colour sensitivity but quite a lot of noise. The NexImage captured the subtle colour of the Moon but didn’t reveal it as well as some of the other cameras, being a little overzealous towards the red end of the spectrum. It also failed to pick out the delicate bluish tint of the Mare Tranquillitatis. The rusty orange hue of Mars was revealed and the belts of Jupiter had their distinctive reddish brown colour. Using an h-alpha filter to image the Sun, the picture appeared red but the camera struggled to pull out subtle surface detail.
We felt the NexImage would be a good camera for beginners. Although the AMCap software is frustrating as a means of control, there are free alternatives available online, which can make using the camera a much happier experience.
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