Explore Scientific Deep Sky
Astro Camera 7.1MP
Explore Scientific has been manufacturing telescopes, mounts and eyepieces for a good while and now it has launched a range of cooled one shot colour (OSC) CMOS cameras aimed at deep-sky astrophotography. Here we take a look at the Deep Sky Astro 7.1MP, which uses an impressive Sony Exmor IMX428 CMOS colour sensor.
The camera is supplied in a tough black plastic case, along with all the accessories that you’ll need to get started, including a software disc to install all the drivers and software. With a nice solid feel, the Deep Sky Astro 7.1MP camera is made from lightweight aluminium anodised in blue. On its back you’ll find the main USB 3.0 socket and a USB 2.0 hub for additional connectivity. There is also a bank of small LED lights and a 12V power socket to attach the included power supply, which is used for the camera’s TEC (thermoelectric) cooling system. Taking off the front cap reveals the Sony Exmor IMX428 CMOS colour sensor, which has a back focus of 17.5mm from the front of the camera.
Setting up the camera is easy once the software is installed, although we did note that the Explore Capture program is contained on a CD and would be better on a flash drive. That said, it’s an extensive piece of software that offers lots of controls and settings. If, like many imagers, you prefer to use your own capture software, there is also an ASCOM driver included for doing so. To begin, we attached the camera to a 115mm Starwave refractor and aimed at the Great Globular Cluster, M13, setting the camera at 60-second exposures with captures to run for an hour. We noticed two issues as the images started to roll in; the first was a glitch in the ASCOM driver causing the colour to be wrong, and the second was a lot of amp glow – an unwanted glow effect in the images that can indicate a possible problem with the camera itself. The next day we contacted Explore Scientific to run through the issues and the company responded quickly with updated drivers that corrected the colour and reduced the amp glow.
At the ready
On the next clear night, we went back to M13 and repeated the capture of 30, 60-second exposures and set about processing the images. There was a marked improvement in the result, with little or no amp glow in the images after processing. To understand why this is important, for the calibration frames to work, any dark frames must be captured at the same exposure and temperature as the light
frames. If there is any difference then amp glow will remain in the images.
With all the clear nights we had we moved on to the spiral galaxies M51 and M81, capturing 60, 60-second exposures using the ASCOM driver to control the camera. As the images came in, we could see the sensor is very capable at capturing targets in a short amount of time. We set the gain to its minimum setting of 100 under ASCOM through the capture run and found that, even in a single exposure of 60 seconds, objects were bright and the stars were sharp. The processed images showed very little noise or unwanted artefacts in the background and, considering the short amount of exposure time, there was plenty of detail. Examining the stars, we noted that we could have reduced the imaging time to around 30 seconds and doubled the amount of exposures; this would have helped to retain star colour and cut down overexposure on brighter targets.
With the Moon shinning bright we switched the camera into Planetary mode and set about capturing some images in Video Capture mode. In Live Capture mode the camera shows quite a lot of green colour, but once the images are processed and colour balanced there is a lot of detail to be seen.
It would be nice to see some extras included with other cameras in this price range, like a heated sensor window, and the amp glow reduced some more.
This would give some more flexibility in the way the camera is used on single-shot astrophotography. However, all in all we were impressed with the images captured and the results obtained with the Deep Sky Astro Camera 7.1MP.