A DMK was placed at the Newtonian focus of an f/5, 6" Newtonian, on a Star Discovery AZ, GOTO mount. A 200 frame, 1s exposure SER file was captured using Nicola Mackin's AstroDMx Capture for Linux on a Linux Mint laptop. The SER file was stacked in Autostakkert! 2 running in Wine, and the resulting 16bit TIFF file was post-processed in the Gimp 2.9.
Screenshot of AstroDMx Capture for Linux, showing M42/43
M43/42 trapezium region
16 bit capture to TIFF and SER files will be implemented before release of the software. This will be of greater values when cameras delivering 12 bits and 16 bits are implemented. Capture cards that offer 16 bit RGB, unfortunately only give 16 bits across all three colour channels 5-6-5 bits per R-G-B, whereas 8 bit RGB gives 24 bits across all three colour channels, 8-8-8 bits per R-G-B.
AstroDMx Capture for Linux now has the ability to capture SER movie files as well as AVI files and TIFF images. The advantage of SER over AVI is that it is possible to save 16 bit images in the SER container. In this experiment, 8 bit images of the 79% waning, gibbous Moon were captured in a SER file through an f/5, 80mm ED refractor with a LUCKY ZOOM HD CMOS camera at the prime focus of the telescope. The software was set to map the YUYV video stream to monochrome by using only the luminance information in the video stream, thus using the colour camera as a monochrome camera.
The SER file was stacked in Autostakkert!2 in Wine, wavelet processed in Registax 6, and processed in The Gimp 2.9.
An 80mm, f/5.5 ED refractor was mounted on an iOptron Cube Pro, AZ GOTO mount. A DMK 21AU04 camera was placed at the focus using a right angle diagonal. M17, the Omega or Swan nebula was imaged using Nicola Mackin's AstroDMx Capture for Linux unde Fedora Linux. 10 x 10s exposures and 10 x 10s dark-frames were captured. Also, 18 x 15s exposures and 10 x 15s dark-frames were captured. All of the images and dark-frames were captured as TIFF files.The two sets of images were dark-frame corrected and stacked in Registax 5.1 running under Wine, the Windows compatibility layer in Linux. The two final 16 bit images, which covered slightly different fields of view, were combined in Hugin and the final image post processed in the Gimp 2.9.
Screenshot of AstroDMx Capture for Linux capturing images of M17
The two images that have been combined in Hugin
Work is currently being undertaken on the AVI library and some finalisation of the reworked GUI before the program is released
Telescope House kindly loaned us a Bresser MicrOcular Full HD CMOS Digital camera to for us to test and implement support in The Linux capture software, AstroDMx Capture that Nicola Mackin and I are developing, primarily for the use of Imaging Source DMK, DFK, DBK series of cameras, hitherto unavailable under Linux. The software works with the primary intended cameras and we are now testing it with and implementing other cameras.
Bresser MicrOcular Full HD Digital camera
The Bresser MicrOcular camera only delivers a compressed Motion-JPEG video stream and it only offers three resolutions: 1920 x 1080; 1280 x 1024 and 1280 x 720. It is
likely that a compressed format has been chosen to deliver a reasonable frame rate at these high resolution formats. However, of the possible compressed formats, Motion-JPEG is a reasonable choice because it is an intra-frame compression system rather than inter-frame compression. This means that each frame is compressed individually, with no reference to other frames in the stream, so there is, for example, no frame prediction involved in the compression.
We have implemented Motion-JPEG in AstroDMx Capture in order to support this camera, which
works now, with AstroDMx Capture, under Linux.
Screenshot of the capture software displaying video from the Bresser MicrOcular Full HD Digital camera
Two AVIs were captured, stacked in Autostakkert2 running under the Windows® compatibility
layer, Wine, and the 16 bit Tiff file post processed in The Gimp 2.9 which can handle 16 bit files.
The seeing was not very good as the Moon was very low in the sky on this lunation. Nevertheless, the camera delivered good results with very little evidence of compression artefacts.
Nicola has done all of the coding for this project and is currently re-working the GUI and working on the open DML AVIX standard. It will only be a short time before the software is released.
Nicola Mackin and I have been working on AstroDMx Capture for Linux and it is fully functional with the DMK and DFK cameras. Nicola has done all of the coding and is now working on optimising the GUI. The software can capture AVIs or TIFF files. The object of this project is to make the DMK,DFK, DBK series of cameras available for Linux.
AstroDMx Capture splash screen
A DMK 21AU04.AS fitted with a 0.5 focal reducer was used with a Skymax 127 Maksutov to image M13. 12 x 6s exposures were made and saved as TIFF files.
Photograph of the live computer screen display
The images were stacked in Registax 5.1 running under the Windows® compatibility layer Wine. The resulting 16 bit TIFF file was then post processed in The Gimp 2.9 which can now handle 16 bit files.
M13 captured by AstroDMx Capture
AstroDMx Capture for Linux is working well. Not only can it control the DMK series of astronomy cameras but also a number of other cameras. It is our aim to make the software compatible with as many USB cameras as possible. The GUI will be reworked to incorporate our new ideas.
This work was done with a laptop running Fedora Linux.
A Skymax 127 Maksutov, F=1500, mounted on a Skywatcher, Star Discovery, AZ, GOTO mount. Although wxAstroCapture was available, I decided to try a capture program that is new to me: WXCam is a capture program that can save uncompressed AVIs and is fast. The burden of this software was the same as with wxAstroCapture, in that it only has limited access to the camera's capabilities via the Linux driver. The camera used was a Phillips SPC900 camera, which was placed at the prime focus of the telescope. Better software is required for serious astronomical imaging.
The capture window displaying part of the Moon to be imaged
Three overlapping regions of the Moon were captured with 1 minute AVIs. The AVIs were stacked in Registax 5.1, running under Wine. The three resulting images were stitched into a mosaic which was also cropped, using Hugin Panorama, a very capable program for making image mosaics. The final mosaic was in each case, post processed in the GIMP (Gnu Image Manipulation Program). This process was repeated for a different region of the Moon.
Sinus Iridum, Plato region
Tycho region
Linux has many of the tools for astronomical imaging and its main burden is suitable drivers.
Testing the 16 bit Atik Infinity Deep Sky USB video camera
An Atik Infinity camera was kindly provided by Atik Cameras for these tests
The Atik Infinity
This camera is optimised for video astronomy. What this means in practice, is that when mounted on a telescope, the output from the camera can be displayed in near real time on the monitor of the computer that is running the Infinity capture software and to which the camera is attached. I tested the mono version of the camera, although a colour version is also available.
The camera is very sensitive and employs the SONY ICX825ALA CCD chip which has very low noise of just 6 electrons RMS and has a quantum efficiency of about 75% in the middle of the visible spectrum. It requires an external, 12 volts power supply and connects to the computer via USB 2.0.
The Atik Infinity has a 16 bit ADC, which is why this camera is fundamentally different from any other camera so far featured in this blog. An image with a 16 bit depth has a possible 65,536 levels of brightness whereas an 8 bit image only has 256 levels of brightness. The upshot of this difference is that it is much easier to saturate 8 bit images than it is to saturate 16 bit images. Consider a single pixel with a brightness value of 1 in an 8 bit image : If we were to sum 256 such images, then this pixel would be at maximum brightness; i.e. it would be saturated. However, if we had a pixel with a brightness value of 1 in a 16 bit image, we would be able to sum 65,536 such images before that pixel will saturate. This means that a 16 bit image will take longer to saturate as photons arrive at the sensor, and that there are a huge numbers of possible brightness states compared with an 8 bit image. The consequences of this are that when an image is stretched (i.e. the brightness values of the pixels are manipulated mathematically) it is possible to reveal subtle gradients in brightness in 16 bit images that would produce more crude steps in brightness gradients in an 8 bit image. With a linear stretch, each pixel is changed by the same factor, but with a non-linear stretch, mathematical functions can be used to increase, for example, faint parts of an image, whilst leaving the brighter parts untouched. 16 bit images are much better suited to this type of processing. The Infinity capture software has a selection of stretching functions, but sometimes parts of the live image appear to be saturated on the 8 bit display, whereas they are not saturated when the saved 16 bit image is stretched in a non-linear way.
The Infinity Capture software was used, but the image processing software provided by Atik was not used in these tests.
The Infinity software was launched, and set to Finder Mode. In this mode, the images are binned 4x4 and exposure is set to 1s. The object of interest is then moved into a suitable position on the screen. The image is noisy and low definition, but allows the object to be detected and positioned:
The software is then set to capture mode and an appropriate exposure (In the case of the Orion Nebula, 5s exposures were suitable with the equipment used) The image capture button was pressed and the images were allowed to stack on screen and then after a period of stacking (38 x 5s exposures in this case), the stacked image that has built up, now containing little noise is saved as a 16 bit file, usually a FITs file. This was a most convenient and pleasing way to capture images.
The Atik Infinity camera was placed at the Newtonian focus of an 150mm, f/5, Star Discovery, Newtonian. on an AZ GOTO mount to observe and capture images in these tests.
The Atik Infinity plus the Infinity capture software should be regarded as a Deep Sky astrovideography and image capture system.
Live stacking of the images allows the observer to see the image noise decrease as each image is added to the stack. Moreover, and most importantly, the Infinity capture software de-rotates the images as they are captured and added to the stack. This means that Alt-azimuth systems like the Star discovery system used here can be used for Deep Sky stacked image viewing and capture.
The captured exposures can be saved and at any time, used by the software in playback mode, which behaves exactly like the images coming in live from the camera. This means that functions such as flipping horizontally, and or vertically can be done later as the saved images are stacked. This can also be a useful feature for teaching purposes.
Images were collected of the Horsehead nebula and stacked on screen. The image was saved as a 16bit PNG file and post processed in Photoshop:
Horsehead Nebula
Capturing and processing the 16 bit Fits images Live view of an image that was saved:
The histogram can be changed on the fly for the displayed image, to reveal different parts of the structure
Using ESO,ESA, NASA Fits Liberator Linear stretch of the image
With a linear stretch, the central part of the image is over exposed. However, this is a camera producing 16 bit Fits files, so there is a lot hidden in the bright parts of the image:
A non-linear stretch of the image (ArcSinh(ArcSinh(x))
Now, none of the image is overexposed.
The image can then be saved out as a 16 bit Tiff file: The 16 bit Tiff image
This 16 bit Tiff image can then be further processed in Photoshop
The Processed 16 bit Tiff image
Finally, the image can be flipped and rotated if required, to give the required view, or the flipping could be done at capture time or in replay mode.
The final image:
An Atik Infinity camera was placed at the Newtonian focus of an AZ, 150mm, f/5 Star Discovery , AZ, Newtonian. 15s exposures were set with image stacking. In both cases the stretching for viewing was set to MeanSD. This gave the best live views but is not applied to the saved images, which are saved as raw FITs files.
Live view of the Infinity software, stacking 15s exposures of M101
The resulting processed image of M101 (Stack of 20x 15s exposures)
Live view of the Infinity software, stacking 15s exposures of M51
The resulting image of M51 (Stack of 20x 15s exposures)
An Atik Infinity camera was placed at the Newtonian focus of a 150mm, f/5, Star Discovery AZ, GOTO Newtonian. Stacked images were captured as FITs files, processed in FITs Liberator and then Photoshop. Click on an image to get a larger view:
M81
M82
M97
M108
M1
An Atik Infinity, 16 bit mono camera was placed at the prime focus of an 80mm, ED refractor. 6 x 30s exposures were stacked live and the resulting image was saved as a 16 bit FITs file. A non-linear stretch was applied in the ESO/ESA/NASA software FITs Liberator, and then further processing was done in Photoshop:
The Orion nebulae
An Atik Infinity camera was placed at the Newtonian focus of a 150mm, f/5, Star Discovery, AZ Newtonian. 20x 15s exposures of the Black-Eye Galaxy were stacked live and then saved as a FITs file. The image was non-linearly processed in the ESO, ESA, NASA Fits Liberator Software, and Photoshop:
The Black-Eye galaxy
The Atik Infinity is an easy camera to use. Together, the Infinity camera and the Infinity software provide a powerful imaging system, that even with small scopes on AZ mounts, can produce good deep sky images. However, the high sensitivity of the camera, in conjunction with the live stacking of captured images, makes the Infinity a delightful tool for individual or shared observing and makes it an ideal camera for outreach activities.
There is also a colour version of the Atik Infinity, which was not tested here.
I have published a review of this camera in Popular Astronomy 3, pp 33-35
The Camera, an ELP, 1.3 Mp, CMOS, USB board camera is available at the time of writing, for £29-99p on Amazon.
Camera re-mounted in a project box
It has been tested here using SharpCap 7 capture software and a 150mm, f/5, AZ Star Discovery Newtonian. The camera was placed at the Newtonian focus of the telescope, and 500 frame AVIs were captured at full resolution of 1280 x 960 pixels. Registax was unable to read the AVIs, which were read into VirtualDub and re-saved as uncompressed AVIs (this does not affect any compression that may be imposed by the camera's firmware).
The first thing to note is that the camera does deliver some compression in both YUYV and MPEG formats, with framerates of 9fps and 15fps respectively. This having been said, the compression is not as severe as in some webcams, and delivers pleasing live views suitable for shared observing. So far, the camera has been tested on the Moon, but not on any planets.
Live Views using SharpCap
The terminator was imaged as a Mosaic of 4 overlapping images of the 55%, waxing, gibbous Moon, derived from 500 frame AVIs.
Terminator of the 55%, waxing, gibbous Moon
Another night, 8 overlapping AVIs of the 84%, waxing, gibbous Moon were captured and the resulting images combined into a mosaic.
84%, waxing, gibbous Moon
Although some compression is evident in these images, it is not sufficient to prevent the capturing of pleasing images, and from producing live images of the Moon that are suitable for shared observing and outreach.
A LN300 video camera, fitted with an IR/UV cut filter was placed at the Newtonian focus of a Star Discovery, f/5, 150mm Newtonian and 150 frame AVIs were captured at 4 different exposures. The AVIs were stacked in Registax and the resulting images were derotated and stacked in Deep Sky Stacker. The resulting image was post processed in Photoshop:
An animation was made of the separate exposures and the final image to show the information that can be extracted from the images when combined.
