Saturday 11 August 2018

Testing the new DMK 37AUX273 USB3.1 Machine-vision camera in AstroDMx Capture for Linux


Following an invitation to make proposals to The Imaging Source to test their new cameras, we have received a DMK 37AUX273 that we selected because it has a number of possible desirable characteristics for astronomical imaging:

Dynamic range 8/12 bit
Video output format 8-Bit Monochrome, 16-Bit Monochrome

Sensor type: CMOS Pregius
Sensor: Sony IMX273LLR
Shutter global
Format 1 / 2.9
Resolution 1,440×1,080 (1.6 MP)
or 640 x 48 ROI
Frame rate 270 fps
Pixel size H: 3.45 μm, V: 3.45 μm
Lens mount C/CS

The DMK 37AUX273 USB3.1 is a very diminutive camera compared with the familiar DMK 21AU04 AS camera. Its dimensions are 36×36×25 mm not including the nosepiece. It currently retails at 286.8 Euro including VAT.




The initial tests were with AstroDMx Capture for Linux before 16 bit output and ROI are implemented for this camera.

Solar and Lunar imaging

DMK 37AUX273 attached to a SolarMax ll 60 BF15 H-alpha scope




The first test was on the Sun using a Coronado Solarmax ll, 60, BF15 H-alpha scope. Two overlapping, 2000 frame SER files were captured at prime focus with AstroDMx Capture for Linux, exposed for the disk and two more exposed for the prominences. The best 80% of the frames were stacked in Autostakkert! 3 and stitched in Microsoft ICE, and wavelet processed in Registax 5.1 all running in Wine. The overexposed prominence images were stitched in Jon Grove’s iMerge running in Wine. The images were post processed and combined in the Gimp 2.10.



Full Size



Another test involved using a 2x Barlow lens screwed on the front of the nosepiece and imaging a region with a prominence. With this arrangement no Newton’s rings could be seen, but they were present if the Barlow lens was mounted normally in the Barlow housing. A 2500 frame SER file was captured exposed for the disk and a second SER file was captured exposed for the prominence. The SER files were stacked and wavelet processed in Registax 5.1 running in Wine. The two images were combined and post processed in the Gimp 2.10.


The camera showed good dynamic range in these experiments.

The best 80% of frames captured of the Palus Somni region of the waxing, crescent Moon were stacked in Autostakkert!3 and wavelet processed in Registax 5.1, both running in Wine. The image was post processed in the Gimp 2.10.


There is no doubt that for lunar and solar imaging, this camera performs well.

Deep sky imaging.

The DMK 37AUX273 was placed at the Newtonian focus of a Skywatcher Explorer 130 PDS 130mm, f/5 Newtonian mounted on a Celestron AVX EQ, GOTO mount.
The DMK 37AUX273 camera had not yet been implemented in AstroDMx Capture for Linux, so the deep-sky imaging had to be done in 8 bits. The software was set up to integrate 10 x 2s, 8 bit exposures into a 16 bit Tiff file. 50 such files were captured of the Swan nebula. 10 matching, 16 bit dark frames were captured. The images were stacked in Deep Sky Stacker running in Wine and the final image processed in the Gimp 2.10

Screenshot of AstroDMx Capture for Linux


The Swan nebula



The eagle nebula was imaged using integrations of 10 x 6s exposures. 15 such exposures were captured along with 5 matching dark frames. The images were stacked in Deep Sky Stacker running in Wine. The resulting image was post processed and cropped in the Gimp 2.10 to show the Pillars of Creation.

The Pillars of Creation in the Eagle nebula



So, first impressions of the camera using AstroDMx Capture for Linux that had not yet had the camera implemented for 16 bits and ROI, are favourable. However, until the camera is fully implemented, no more information is available.

After 16 bit capture was implemented, A stack of 45, 30s exposures yielded the following image which is cropped from the middle of the frame to avoid currently intractable amp glow regions.

ROI has now been implemented.