The DMK 31AU03.AS monochrome CCD camera has a blue body and when doing solar imaging it absorbs heat from the solar radiation and becomes very hot.
To protect the camera from excessive heat it was wrapped in aluminium foil to act as a reflector.
The camera attached to the scope and reflecting sunlight
This had the desired effect, and the camera ran much cooler than on previous occasions.
The DMK 31 AU03 camera was placed at the focus of the CaK PST which was mounted on a Celestron AVX mount.
AstroDMx Capture for Linux was used to capture two 1000-frame SER files of overlapping regions of the Sun. The SER files were stacked in Registax 5.1 (Registax is able to stack monochrome SER files but not colour SER files) Registax calls SER files 'LuCam recorder SER' files (because the SER format was originally developed by Heiko Wilkens for Lumenera cameras). The resulting images were stitched into a 2-pane mosaic with Microsoft ICE. The resulting image was post-processed in the Gimp 2.10.
Screenshot of AstroDMx Capture capturing a SER file
Final image of the Sun in Ca K-line light 393.4 nm
There are 6 numbered active regions visible in this image and they are divided into two bands, one in the north and the other in the South. From left to right at the top half of the image are active regions AR2846, AR2848, AR2842. In the bottom half of the image are active regions AR2849, AR2847 and AR2845.
These regions are associated with pale areas of high magnetic flux.
The DMK 31AU03.AS CCD camera has an unfortunate limitation not shared by many other Imaging Source cameras: It will only work with a computer that has a true EHCI USB controller and will not work at all with computers that only have xHCI USB controllers. It is not immediately clear why this should be so, and it is unlikely that the Imaging Source will have any interest in rectifying this. EHCI USB controllers only support USB 2.0 speeds (480 Mbit/s); whereas xHCI USB controllers support all USB speeds, USB 3.0 (4.8 Gbit/s) including Super Speed (5 GB/s). xHCI is supposed to be perfectly backwards compatible, but in cases like the DMK 31AU03.AS, this is clearly not so. It is likely that the firmware does not adhere perfectly to the USB 2.0 standard, which renders it inoperative in a computer with only an xHCI controller. For this reason we use this camera with a Thinkpad X230, which has both types of USB controllers.
The procedure described here of covering a camera with aluminium foil in order to reduce the absorption of heat from solar radiation whilst solar imaging, is a simple. yet effective solution for a simple camera body design such as that of the DMK. If a more complex design, incorporating fins or vents is incorporated into the camera, there is no reason why the aluminium foil solution should not work, as long as vents and features to aid air flow over the camera body are not obstructed.
