AstroDMx Capture in a Chromebook via Crouton

In recent months I have written a number of articles about using AstroDMx Capture in a Crostini Linux virtual machine on a Chromebook. The Crostini Linux environment is now stable on Chromebooks. We have shown that it is easy to set up Linux under Crostini and to install a number of important Linux programs for astronomical imaging. We have also shown how to install the Windows compatibility layer Wine so that we can run Windows programs such as Autostakkert! And Registax on a Chromebook.

Crostini

Installing AstroDMx Capture for Chrome OS on the Crostini virtual Linux container allows us to capture images and movies. There are, however, limitations: 

One limitation is that responsiveness is slow, but the program is still very usable. The slow responsiveness is not surprising considering the fact that Chromebooks are, in general, low powered computers with little RAM and Storage, and with low end processors. On top of this, the Linux environment is running inside a virtual machine running in Chrome OS. All of these facts lead to performance penalties. Of course, there are some Chromebooks now available with much higher all round specifications and coming at commensurately higher prices. No doubt the software will be more responsive on these machines. 

Another limitation is that the only cameras that we have found to work properly in the Crostini virtual Linux environment on Chromebooks have been the SVBONY SV305 family of CMOS astronomy cameras. It is not immediately obvious why these cameras work well and others do not. Possibly it is due to the adherence to standards, but the reason could lie elsewhere. The fact remains that at the time of writing, cameras have not been implemented by Google in Crostini. The cameras to which I am referring to are UVC cameras, and most astronomy cameras are not UVC devices.

Crouton

For several years there has been a different way of running Linux on a Chromebook. This system is called Crouton.

Crouton was originally created by Google employee David Schneider. When you use Crouton, you're actually just running one operating system: Linux. However, you are running two environments with Chrome OS.

Crouton stands for Chromium OS Universal Chroot Environment

Crouton is a set of scripts that form a Chrome OS  chroot generator.

What's a chroot?

Chroot stands for Change root. The chroot call originated in Unix 7 in 1979 so it is not a new concept. Unlike Crostini, a chroot is not a virtualisation system.

However, like virtualisation, a chroot provides the guest OS (In this case Debian Linux) with its own, isolated file system to run in, allowing applications to run natively in a different environment from the host OS. Unlike virtualisation, you are not booting a second OS; instead, Debian Linux is running using the Chromium OS system and kernel and effectively uses the Chrome browser as its X-server as a GUI for the running application. The benefit to this is that there is no speed penalty since everything is run natively, and you don’t use lots of RAM to boot two operating systems at the same time.

To visualise this we must be aware that the Chrome OS has its own file system with its own root. It is, basically, an operating system with a Linux kernel and using the Chrome browser as its desktop environment. 

Crouton sets up another totally isolated file system with its own root on the computer and installs Debian Linux  into it. This Debian does not have its own kernel, it uses the Linux kernel of Chrome OS. The chroot changes the root to the Debian OS and it is within this system that programs are installed and run natively, without the performance penalties associated with virtualisation.

We have set up Crouton on a Lenovo Chromebook with an AMD A6 processor, 4GB RAM and 64BG of eMMC storage; a fairly modest Chromebook.

We installed AstroDMx Capture for Linux into the Debian system and were able to run it natively with no performance penalties.

There are three limitations that are not too important at the moment:

First, it is not possible to take a screenshot that includes the preview screen of AStroDMx Capture due to the way it is rendered by the Crouton system.

Second, it is important NOT to try to close the software in the usual way by clicking on the cross at the top right of the display. In fact, this is NOT a control to close down AStroDMx Capture; it is a control to close down the Chrome browser in which AstroDMx Capture is being displayed. It is necessary to close the software via the file menu.

Third, we have found that the QHY series of cameras will not work with the Crouton system. QHY cameras have to have their firmware uploaded each time they are started, and it is probably this process that is currently inhibiting the use of these cameras. Nonetheless, Crouton allows the use of many cameras that are just not possible to use under Crostini.

This is a work in process and it is not considered that these three  limitations are important at the moment

Unlike with the Crostini virtualisation system, we are not limited to using the SVBONY SV305 series of cameras, and in the current test we used a Touptek Toupcam GPCMOS01200KPF camera. 

Testing AstroDMx Capture for Linux using Crouton

An f/5.5, 80mm, ED Ekinox Eklipse refractor was mounted on a Celestron AVX mount and a Touptek Toupcam GPCMOS01200KPF camera was placed at the focus.

A Lenovo Chromebook with an AMD A6 processor was used running a Crouton chroot with Debian Linux, a way of running Linux on a Chromebook that does not involve the Crostini virtualisation system.

AstroDMx Capture for Linux was run natively in the chroot and was used to capture 60 x 15s exposures of M15 using the RGB48, 16-bit format along with matching dark frames.

The data collected were processed on a separate computer as this was simply a test of AstroDMx Capture with Crouton. However, it would be possible to install all of the software required to do the stacking and post-processing if this was to be a system that would be used for imaging on a regular basis.

Equipment used

Final image of the globular cluster M15

To set up Crouton on a Chromebook, you have to do a Powerwash and set the Chromebook in Developer mode. It is therefore important to back up any files you may have stored locally. Developer mode is less secure than the normal mode and Chrome OS reminds you of this when you turn on the computer by making some beeping sounds. (These can be avoided by pressing ctrl and d during power on). However, remember, that you are working with Linux which is pretty secure in its own right, and you are doing this in order to get more out of your Chromebook and use it to run AstroDMx Capture for Linux natively. Moreover, if you don’t invoke Crouton, you still have the full functionality of your Chromebook albeit in the slightly less secure Developer mode. 

Implementing Touptek cameras in AstroDMx Capture

Nicola is in the process of implementing Touptek cameras in AstroDMx Capture for all platforms. This implementation will be part of the next release of AstroDMx Capture.

We tested a TOUPCAM GPCMOS0200KPF camera fitted with an SVBONY UV/IR cut filter.

A skymax 127, modified for motor-focus, was mounted on a Celestron AVX mount. The TOUPCAM GPCMOS0200KPF was placed at the focus.

AstroDMx Capture for Linux was used to capture 5000-frame SER files in RGB24 of selected regions of the 92.2% waxing Moon. The imaging was done through high, thin clouds, which was far from ideal, but was adequate for these tests.

Click on an image to get a closer view

Equipment used

Screenshot of AstroDMx Capture for Linux capturing data on the Tycho region of the Moon

The best 25% of the images in the SER files were stacked in Autostakkert!, wavelet processed in Registax 6 and post-processed in the Gimp 2.10.

Final image of the Tycho region

Craters Tycho, Schiller and Clavius are all very clear.

Screenshot of AstroDMx Capture capturing a 5000-frame SER file on the Sinus Iridum, Mare Imbrium region of the Moon

Final image of the Sinus Iridum, Mare Imbrium region

Sinus Iridum, Mare Imbrium, The Alpine valley, Craters Plato, Aristillus, Autolycus and Archimedes are all visible in this image.

Final image of the Copernicus, Kepler region of the Moon

Final image of the Gassendi region of the Moon

Final image of the Mare Serenitatis region of the Moon

In conclusion, the Touptek TOUPCAM GPCMOS0200KPF camera worked well with AstroDMx Capture.

RGB48 and a new DMxWB Auto white balance function in AstroDMx Capture

Testing the new DMx WB Auto white balance function in AstroDMx Capture.

This improved version of the DMx Auto WB function with automatic brightness compensation will be in the next release of AstroDMx Capture for all platforms, as will the 16-bit format RGB48 for cameras that offer it, such as Altair and Touptek cameras.

When capturing RAW data with cameras such as Altair and Touptek, The preview and captured images have a green tint as we have mentioned previously. To some extent, this can also happen with Atik colour cameras.

Altair describe this as normal and what would be expected when capturing true RAW data. The green tint can be removed in post processing.

However, as we have pointed out previously, sometimes the preview image is especially important, for example, for outreach work. Moreover, if one is doing live-stacking by combining AstroDMx Capture with DSS Live, it would be desirable to have white balanced data being live-stacked.

Nicola has solved this problem in two ways.

1. Implementation of RGB48 capture. RGB48 is a 16-bit colour format for which there is a white balance control as there is in RGB24, the 8-bit format. The RGB48 format is generally not available in other capture software, and is not available for many camera types.
2. Implementation of DMx Auto WB for RAW16 and RAW8 captures which works with Fully debayered data. The DMx Auto WB can be turned on or off for the preview and it can also be turned on or off for saving.

RGB48 for a camera such as an Altair or a Touptek can be selected when the camera is connected.

The format can also be changed from within the program when it is running.

This mode has a one touch white balance.

Demonstrating the DMx Auto WB function

We used an Altair GP-CAM 225C camera at the focus of a Skymax127 that was mounted on a Star Discovery AZ mount. Using AstroDMx Capture for Linux, a 2000-frame SER file was captured of the Moon, which during the current lunation, is extremely low and was only just visible over the mountain opposite our site. As a consequence, seeing was very poor due to the low altitude of the Moon and the heat rising off the mountain. Nevertheless, conditions were good enough to perform a test.

Animation showing AstroDMx Capture streaming lunar data with the DMx Auto WB turned on and off

It can be seen that when the DMx Auto WB is on, the image loses its green tint and retains its brightness because the Brightness Compensation is turned on. Also, when the DMx Auto WB was on we set it to apply to save data.

AstroDMx Capture for Linux capturing lunar data as a 2000-frame SER file

Final image of the Posidonius, Hercules, Atlas, Mare Serenitatis region of the Moon

A closer look at the DMx Auto WB function

We focused a refractor fitted with an Altair GP-CAM 225C on the top of an electricity transformer pole across the valley, using RAW16 with AstroDMx Capture for Linux

There are three images in this animation.

1. DMx Auto WB OFF (This shows a green tint)
2. DMx Auto WB ON (Just for the display)
3. DMx Auto WB ON (For display and applied to saved data)

When the DMx Auto WB is on, the Brightness compensation is turned on. If this is turned off, the white-balanced image will be dimmer than the un-white-balanced image.

The histogram shows the histogram of the data to be saved and is shown in closeup in the following image.

From Left to Right:

1. DMx Auto WB OFF
2. DMx Auto WB ON but not applied to saved data
3. DMx Auto WB ON and applied to saved data.

The DMx Auto WB function is there for the imager to use or not, and if it is used, it can be applied to the saved data as well as the preview, or it can just be applied to the preview.

AstroDMx Capture maintenance release Version 1.2.6

Nicola has released an AstroDMx Capture maintenance release Version 1.2.6

This release addresses a bug and makes two improvements.

Mutatis mutandis

• Fixed: SVBONY SV305 gain/exposure bug
• AstroDMx's custom white balance function can now be applied in a non-destructive way. That is, applied just to the preview screen and leaving the saved data unchanged; or it can be applied to the saved data.
• Atik Fast Preview is now automatically disabled during capture

Feature release of AstroDMx Capture for all platforms Version 1.2.4

Nicola has released a feature release of AstroDMx Capture for all platforms Version 1.2.4.

Mutatis mutandis

Version 1.2.4

There are a number of significant changes in this version of AstroDMx Capture 1.2.4

• Added: Fan control for ZWO cameras
• Added: Dew heater control for ZWO cameras
• Added: Dew heater control for Altair cameras
• Added: Trigger mode for Altair cameras
• Added: RGB48 16 bit pixel format for Altair cameras
• Added: Black level value to FITS metadata
• Added: Bayer pattern value to FITS
• Added: Altair support on Raspberry PI 32 and 64 bit
• Major refactor to allow arbitrary length exposures when the camera's exposure units operate in microseconds
• Fixed: Bug associated with some ZWO cameras when operating in long exposure mode
• Fixed: Bug associated with AVI's on Windows
• Updated: ZWO SDK
• Updated: QHY SDK
• Updated: SVBONY SDK
• Updated: ZWO Filterwheel SDK
• System Information dialog has been updated
• Improved the debugging output
• The USB speed parameter is now automatically reduced to the minimum when operating in long exposure mode
• Other bug fixes and improvements

RGB48 16 bit format

Most astronomical cameras offer 8 bit RAW, 16 bit RAW (from 12, 14 or 16 bit ADCs), sometimes 8 bit mono (for a colour camera) and RGB24, which is an 8 bit format (8 bits per colour channel).

There are, however, some cameras such as the Altair cameras, that also offer RGB48. This is a 16 bit format (16 bits per colour channel). As with 16 bit RAW, RGB48 data can come from 12, 14 or 16 bit ADCs), the image data are put into a 16 bit image container. In the case of AstroDMx Capture, the 16 bit image containers can be FITS, TIFF, PNG or SER files.

In addition to Gain, Black Level and Exposure, the RGB48 format has access to all of the controls that the RGB24 has, for example, Gamma, Brightness, Contrast, Hue, Saturation, Colour Temp, Colour Tint, and One Touch white balance.

It could be argued that these kinds of adjustments can be made in post-processing, which is true. However, it is quite satisfying to have a preview image that more closely resembles the final image.

Being a 16 bit format the preview images are controlled by the 16 bit display controls and also the non-destructive display controls which are all designed to make the 16 bit images visible in preview.

The Moon with a Chromebook, AstroDMx Capture for Chrome OS and an SV305M Pro camera.

A Skywatcher Star Discovery 150mm, f/5 Newtonian was mounted on a Star Discovery AZ GOTO mount and an SVBONY SV305M Pro was placed at the Newtonian focus.

The Star Discovery scope and mount used

A Lenovo Chromebook S345 with 4GB RAM and a 64GB eMMC drive and an AMD A6 CPU was used for capturing lunar data. The Chromebook was running Crostini with Linux and had installed all of the software needed to capture and process the data.

AstroDMx Capture for Chrome OS was used for capturing. It should be noted that at the time of writing, the only cameras that will work are the SVBONY SV305 series of cameras. At this stage we don’t know whether it will become possible to use other makes of camera in Chrome OS like this, or indeed, whether future updates of Chrome OS might break its present capabilities.

The software installed in the Crostini Linux container includes:

• AstroDMx Capture for Chrome OS (native Linux)
• Wine, Windows compatibility layer (native Linux)
• Autostakkert! 2 for stacking (using Wine)
• IRIS for wavelet processing (using Wine)
• The Gimp 2.10 for post-processing (native Linux)
• Hugin Panorama Creator for stitching image panes together (native Linux)

AstroDMx Capture for Chrome OS was used to capture 1000-frame SER files of three, overlapping regions of the Moon covering the terminator side of the 98.5% waxing Moon, but not the whole lunar disk.

Click on an image to get a closer view

AstroDMx Capture for Chrome OS capturing a SER file of the Plato/Sinus Iridum region of the Moon.

Final image of the Plato/Sinus Iridum region

AstroDMx Capture for Chrome OS capturing a SER file of the Copernicus/Kepler region of the Moon.

Final image of the Copernicus/Kepler region

AstroDMx Capture for Chrome OS capturing a SER file of the Tycho region of the Moon.

Final image of the Tycho region

Hugin Panorama Creator was used to align and stitch the three panes of the terminator side of the Moon into a mosaic.

This is another demonstration that a Chromebook with Crostini Linux is capable of capturing and processing astronomical images using an SVBONY SV305 series camera and AstroDMx Capture for Chrome OS.

Combining H-alpha and Ca K-line solar images

Imaging was done with a CaK PST, a Solarmax II, BF15, H-alpha scope and a DMK  31AU03.AS CCD camera, mounted on a Celestron AVX mount.

The data were captured as SER files with AstroDMx Capture.

Click on an image to get a closer view

Screenshot of AstroDMx Capture saving a SER file of Ca K-line solar data

Screenshot of AstroDMx Capture saving a SER file of H-alpha solar data

The SER files were stacked in Autostakkert!, wavelet processed in Registax and post processed in the Gimp 2.1.

Results

Ca K-line light

H-alpha light

The Ca K-line and H-alpha images were combined in Picture Window Pro 2.5 running in Wine, using translate, rotate and scale to exactly match the features on both images and to blend the images together.

H-alpha plus Ca K-line merged

Combining Calcium and H-alpha images in this way allows one to see the different types of structure revealed by each wavelength.

Jupiter and the Moon with AstroDMx Capture and an Altair GP-Cam 225C CMOS camera

A Skymax 127 Maksutov was mounted on an AVX mount and an Altair GP_CAM 225C CMOS camera was placed at the focus. For imaging Jupiter, the lens from a x2 Barlow was attached to the camera and for imaging the Moon, no Barlow was used.

AstroDMx Capture for Windows was used to capture the data. Stacking was done in Autostakkert!, wavelet processing was done in Registax and post processing was done in the Gimp 2.10.

Click on an image to get a closer view

Jupiter with Io shadow transit

Jupiter with the GRS and Io plus shadow transit

Screenshot of AstroDMx Capture capturing lunar data

Lunar images

The second image of each pair has been chrominance enhanced to reveal variation in the mineralogy of the lunar surface.

Plato, Sinus Iridum region

Herschel, Ptolemaeus region.

Copernicus, Kepler region

Archemedes, Aristillus region

Tycho, Clavius region

The Altair GP-CAM worked very well with AstroDMx Capture and works well on macOS, Linux, and 32bit Raspberry Pi Linux.

New feature release Version 1.0.5 of AstroDMx Capture and implementation of the Altair Hypercam 294C PRO 4GB TEC camera

New feature release of AstroDMx Capture with implementation of the 

Altair Hypercam 294C PRO 4GB TEC OSC CMOS camera.

Feature release of AstroDMx Capture for all platforms

Version 1.0.5

Mutatis Mutandis.

Nicola has released version 1.0.5 of AstroDMx Capture for Windows, macOS and Linux (including the Raspberry Pi) and Chrome OS.

Click on an image to get a closer view.

There are a number of significant changes in the new version

• Altair camera implementation. (The actual camera implemented was the Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera).
• Added: PNG output.
• Automatic white balance control (DMx Auto WB) independent of any camera specific white balance controls.
• Panning mode with scrollbars in hardware acceleration (drag-panning is still available)
• Thermal controls moved into their own control group.
• Improved cooling functions.
• Automatic selection for display performance.
• Sensor temperature in log and FITS metadata.
• Windows: changed colour of the control group titles.
• SVBONY and QHY SDK version increases.
• Automatic implementation of the correct version of AstroDMx Capture for Linux, based on the CPU and the version of the glibc dependency on the user’s computer. This removes the possibility of a user downloading the wrong version.
• Bug fixes.

DMx Auto WB

Some cameras such as the Atik 320E OSC CCD camera  and some others such as the Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera, have a green cast to their images captured in RAW mode.

 Altair describes this as a natural result of using true RAW, and the green cast has to be removed in post processing.

AstroDMx Capture now has an option to apply an auto white balance (DMx Auto WB) in the preview AND the saved data when capturing from RAW data. DMX Auto WB can be turned on or off by the user.

The equipment used for the tests on DMx Auto WB. The camera used was an Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera

The camera was kindly loaned to us by Dr Simon Helan of the Swansea Astronomical Society so that it could be implemented in AstroDMx Capture.

Screenshot of AstroDMx Capture for Windows preview of M27 with DMx Auto WB OFF with an Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera, a Skywatcher 130PDS f/5 Newtonian reflector mounted on a Celestron AVX GOTO EQ mount

It can be seen that there is a green cast to the preview image which is confirmed by the histogram.

Screenshot of AstroDMx Capture for Windows preview of M27 with DMx Auto WB ON with an Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera, a Skywatcher 130PDS f/5 Newtonian reflector mounted on a Celestron AVX GOTO EQ mount

It can be seen that with DMx WB ON there is now no green cast, which is confirmed by the histogram.

Final image of M27 with an Altair Hypercam 294C PRO 4GB TEC

Screenshot of AstroDMx Capture for Windows capturing data on M17 with DMx Auto WB OFF an Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera, a Skywatcher 130PDS f/5 Newtonian reflector mounted on a Celestron AVX GOTO EQ mount.

There is a strong green cast to the image which is confirmed by the histogram.

The brightness of the preview is due to the transform and other controls being applied to the preview. 

Screenshot of AstroDMx Capture for Windows capturing data on M17 with DMx Auto WB ON an Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera, a Skywatcher 130PDS f/5 Newtonian reflector mounted on a Celestron AVX GOTO EQ mount.

With DMx WB ON there is no green cast that is confirmed by the histogram.

The same transform and preview image controls are being used here as in the previous screenshot but DMx WB is ON.

Final image of M17 with an Altair Hypercam 294C PRO 4GB TEC

Screenshot of AstroDMx Capture for Windows capturing data on M16 with DMx Auto WB ON an Altair Hypercam 294C PRO 4GB TEC 14-bit CMOS camera, a Skywatcher 130PDS f/5 Newtonian reflector mounted on a Celestron AVX GOTO EQ mount.

Final image of M16 with an Altair Hypercam 294C PRO 4GB TEC

In a sense, it doesn’t matter whether the white balancing is done before or after capture, but a more pleasing and realistic preview of the image is obtained with the DMx Auto WB ON.

During post processing the removal of the green cast is no longer an issue and other aspects of the image can be concentrated on.

However, if live tracking and stacking was being done by using AstroDMx Capture with DSSL (Deep Sky Stacker Live), pre-capture white balancing would be essential for electronically assisted astronomical viewing, possibly for outreach and general appreciation of the accumulating stacked image. DMx Auto WB ON gives an altogether more satisfying imaging experience than when it is not used.

See my two x-bit blog articles for details on live stacking with AstroDMx Capture and DSSL.

Click on the link to see the full article

Setting up AstroDMx Capture for Windows and Deep Sky Stacker Live (DSSL) to work with each other.

Live deep sky image stacking with AstroDMx Capture for Windows and Deep-Sky Stacker Live.

With AstroDMx Capture now weighing in at more than 66 KLOCs of active code plus 11K lines of internal documentation over 5 operating system platforms, it has been an exhausting time for Nicola, bringing it to release Version 1.0.5.