End of the line for ChromeOS support with AstroDMx Capture

With Regret:

Due to recent changes made to ChromeOS by Google, Nicola will no longer be able to support ChromeOS with AstroDMx Capture. Changes in the ChromeOS operating system have resulted in incompatibilities in the Crostini virtual System. ChromeOS is increasingly including portions of the Android stack, like the Android Linux kernel and Android frameworks. This is a significant shift in the underlying architecture and it is most likely this that has resulted in the problems that now exist. The pass-through of USB devices to the Linux virtual system has always been problematical, but the problems seem to now be intractable. It may be possible to stream images at very low resolutions such as 800 x 600, and maybe only though USB 2.0 cables, but this would hardly be useful for most purposes. This is regrettable, but it seems that ChromeOS is no longer what it used to be and that the changes to the OS are increasing. The problems are not with AstroDMx Capture!

Some time ago, on the AstroDMx Capture website this deterioration of the capability of ChromeOS was documented and it was stated that the SV505C did not work under ChromeOS and cautioned that there was no guarantee that other cameras would now work.

Due to the fact that ChromeOS updates are mandatory and that it is not possible to install an older version, the ChromeOS versions of AstroDMx Capture will soon be removed from the AstroDMx Capture website.

Solebat excitando dum duravit.

Can you believe what you see?

There are many sayings about seeing and believing or knowing. The three examples below are pertinent to our discussion here:

"Seeing is the key to knowing". This emphasises the importance of direct observation in determining what is real or true.

"Seeing is the touchstone of reality". This implies that seeing something first-hand is the ultimate measure of its reality or truth.

"To see it is to know it". This suggests that observing something personally provides a level of certainty that other forms of evidence may not.

What we are thinking about here concerns what you see on your computer screen when you look at an astronomical image that you or someone else has processed. Questions arise about the image: 

If you have processed the image, will it look the same to someone else who is viewing it on their computer monitor not your own? Similarly, if someone else has processed an image on their computer will it look the same to you on your computer screen as it would if it is viewed on their computer screen; and, if not, why not?

Our three example sayings above are ultimately concerned with what you know when you look at something (in our case on a computer screen), and the question arises as to what you actually know if the object appears different (on a different computer screen).

How could the same image appear different on different computer screens? And if it does, which screen if any, is giving the correct presentation?

The answer of course is that the two monitors are calibrated differently and 'ay, there’s the rub', as Hamlet might say. Which monitor is showing an image that is closer to the truth?

There is no way of knowing unless the monitors are deliberately calibrated.

I refer the reader to a blog article that I published on 20 June 2021 entitled “Monitor calibration - Beauty is in the eye of the beholder”

The complete article can be seen Here

The current article is a sequel to the 2021 article.

The Importance of Using a Calibrated Monitor for Deep Sky Astronomical Imaging

When working with deep sky astronomical images, the precision and quality of your monitor’s display can make a world of difference. Not all monitors are equal and it is often the case that more expensive monitors come with better calibration than cheaper monitors. Laptop monitors have fewer controls that can be used to make adjustments but can still be calibrated.

Calibration produces an ICC profile for the monitor which is stored on the computer. According to the International Colour Consortium (ICC,) an ICC profile is a set of data that characterises a colour input or output device. The profile describes the colour attributes of a particular device. A device that displays colour can be assigned a profile, and this profile defines the colour gamut that will be displayed by this device.

How will an image prepared on a calibrated monitor appear on an uncalibrated monitor?

When viewing an image prepared on a calibrated monitor on an uncalibrated monitor, the differences can be quite noticeable. Here are some potential issues you might encounter:

1. Colour Accuracy: The colours might appear different, less vivid, or even distorted. For instance, subtle shades of nebulae might not be accurately represented.

2. Brightness and Contrast: The image could appear too bright or too dark. Details in both the shadows and highlights might be lost, affecting the overall quality and visibility of fine details.

3. Gamma: Differences in gamma settings can alter the way tones and mid tones are displayed. This can affect the smoothness of gradients and the overall balance of the image.

4. White Balance and colour temperature might shift, making the image appear warmer (more yellow/red) or cooler (more blue).

To ensure your deep sky images look their best across various devices, it is a good idea to make sure any critical viewing or sharing is done on calibrated monitors. 

Calibrated monitors have:

1. More accurate Colour Representation

Deep sky images capture delicate details and variations in colour that are crucial for both scientific analysis and aesthetic appreciation. A calibrated monitor ensures that the colours you see on-screen are as true to the actual data as possible, allowing you to make precise adjustments without misinterpreting hues.

2. More consistent Brightness Levels

Calibration also stabilizes brightness levels across your display. For deep sky imaging, where faint stars and nebulae often blend into the dark background, having consistent brightness levels means you won't lose detail in the shadows or overexpose brighter areas.

3. More reliable Contrast and Tonal Gradients

Deep sky astronomical images feature a wide range of tonal gradients from the darkest regions to the brightest stars. A properly calibrated monitor maintains reliable contrast and tonal range, making it easier to distinguish between subtle differences in luminosity and structure within your images.

4. Professional Consistency

If you share your images with other astronomers, researchers, or even the general public, ensuring that everyone sees as near as possible, the same quality and details is crucial. Calibration provides professional consistency, allowing your work to be viewed more accurately across different devices and platforms.

5. Enhanced Post-Processing

Accurate colour representation, brightness, and contrast are vital for effective post-processing of astronomical images. A calibrated monitor ensures that your adjustments and enhancements are based on true data, leading to better final results without unintentional distortions or inaccuracies.

How to Calibrate a Monitor

Investing in a good hardware calibrator (which need not be overly expensive. The Datacolor Spyder at the time of writing can be obtained from the manufacturer for GBP 129) and using calibration software are the best ways to ensure your monitor displays accurate colours and brightness. Follow these steps for a basic calibration process:

Calibration is best done in a neutral lighting environment with minimal glare.

Use Calibration Hardware and Software: Devices like the Datacolor Spyder that we use, paired with calibration software, can guide you through the calibration process.

Calibration device

Calibrating a monitor with a Datacolor Spyder 5 calibration device

Recalibrate the monitor from time to time, as display characteristics can change over time.

In conclusion, a calibrated monitor is a necessity for anyone doing deep sky astronomical imaging. It ensures that the true intricacies of the deep sky are as accurately represented and analysed as possible.

Many professionals recommend embedding ICC profiles within your images to provide a more consistent viewing experience.

How to embed an ICC profile in an image using Gimp 2.10

Locate the ICC colour profile that the monitor calibration created. Copy it to a convenient location.

Follow the following workflow:

Image

  Color Management

   Assign Color Profile

     Assign (search for and select the ICC profile that you placed in a convenient location)

       Assign

The image now contains the ICC colour profile.

There is a plethora of display devices of wide-ranging quality that there is never a guarantee that what we see on our monitors will be the same as what is seen by others on their monitors, even if the above procedures have all been done; but if they have been done, we will be seeing closer representations of what the image producer intended than if they have not been done!

Using free software to process Astronomical image data

Free as in Free Beer

When amateur astronomers discuss the software that they use to process their image data there is often an 'elephant in the room'; that being the idea expressed by the saying 'you get what you pay for'. The assumption here is that paid-for software is in some way superior to free software and that the free software is somehow a 'poor man's substitute'.

Let's get rid of this elephant before we proceed. 'You get what you pay for' is totally irrelevant to free software. While this saying holds true in many commercial contexts, it is irrelevant when it comes to free software. Let's see why:

Open Source and Collaboration

Free software, particularly open-source software, thrives on collaboration and community contributions. Here are some key aspects:

Community Contributions: Open source projects may benefit from many contributors worldwide who continuously improve the software. This collaborative effort can lead to higher quality software compared to commercial products developed by a limited number of in-house developers.

Peer Review: The open-source model allows peer reviews and audits, ensuring that bugs are quickly identified and resolved. This peer-to-peer scrutiny often results in more secure and reliable software.

Transparency: Open-source code is transparent, allowing users to verify the software's security and functionality themselves, which is often not possible with proprietary software.

Motivation Beyond Profit

The motivation behind creating free software is often driven by goals other than profit. This includes:

Innovation and Experimentation: Developers create free software pushing technological boundaries, experiment with new ideas, and solve specific problems.

Community and Sharing: Many free software projects are built on the principle of sharing knowledge and tools with the community, fostering collective growth and learning.

User Empowerment: Free software often aims to empower users by giving them control over their tools and data, respecting their freedom and privacy.

Quality and Professionalism

Professional Development: Many free software projects are developed by experienced individual professionals and even large organizations. For example, Linux, a widely-used open-source operating system, is maintained by a global community of skilled developers, including contributions from major companies like IBM, Intel, Microsoft and Google.

Reliability and Performance: Free software can be highly reliable and performant. Apache HTTP Server, VLC Media Player, Gimp and Blender are all examples of free software that are trusted and used by millions worldwide.

Advert-ware and mixed-model software

There is a plethora of web-based software that displays adverts. Photopea is one such free to use program that places adverts on the right hand side of the window, essentially out of the way. The software is extremely powerful and can be changed to subscriptionware if the user wishes to remove the adverts and become free from the few restrictions imposed such as background removal can only be done once a day in free mode.

Donationware

Voluntary Contributions: Donationware is a model where users are encouraged to contribute financially to the software's development on a voluntary basis. This allows the software to remain free for all users while providing a way for those who can and want to support the project to do so.

Sustainable Development: Donations can help sustain the development of the software by providing financial support for developers and covering costs such as hosting or additional tools.

Community Support: Users who donate often feel more invested in the project, fostering a stronger sense of community and encouraging ongoing contributions.

Conclusion

The notion that "you get what you pay for" does not apply to free software due to its unique development model, community-driven improvements, and motivations beyond profit. Free software often matches or even surpasses the quality of proprietary counterparts, proving that value and cost are not always directly correlated.

The free software that we are going to use here are:

ASI Studio developed by ZWO the commercial astronomical equipment company. The software suite was produced by ZWO to work with its own imaging systems, but some of the programs in the suite such as ASI DeepStack can be used to register, calibrate and stack RAW images from astronomical cameras and ASI FitsView which can be used to view Fits files.

GraXpert is an open-source astronomical image processing tool developed by Steffen Hirneisen. This software has AI components. It removes gradients and denoises astronomical images. At the time of writing there is an alpha version that can also preform deconvolution. No doubt this will make its way into the stable releases in the future.

Siril is An  open-source advanced tool for astronomical image processing and is developed by a team of contributors from the Free Astro community. The project is led by Cyril Richard, who is actively involved in its development.

Gimp is an open-source free image processing program with a huge developer base and which rivals very expensive and well known subscription software. It also has powerful plugins such as G'MIC and Starnet++.

Cosmic Clarity suite is donationware developed by SetiAstro. Its tools that we shall use are AI based sharpening and denoising components.

Although Siril can be used to calibrate and stack data, we are not going to use it for those functions here, instead we are going to use it for Photometric Colour Calibration of our stacked image. ASI DeepStack will be used for calibrating and stacking data because it provides the simplest and fastest way of doing this for monochrome and RAW colour data from astronomical cameras.

The data and equipment

The data used in this article were captured by AstroDMx Capture using two telescope systems, two cameras and two filters.

System 1

William Optics 81 mm ED APO refractor

ZWO Electronic Focuser

Altair magnetic 2" filter holder

Altair quadband filter.

Altair Hypercam 533C 14 bit OSC CMOS camera

SVBONY SV165 Guide scope

QHY-5II-M guide camera

JJC DHS-1 USB Lens Heater Strip x 3 (For imaging scope, guide scope and ZWO electronic focuser)

Multi USB 4 Port Plug Adaptor

5A 12V Power adapters x 3 (For EAF, Cooled CMOS camera and Lens Heater Strips)

Mains extension lead

AVX GOTO mount which was controlled by AstroDMx Capture via an INDI server running on the imaging computer indoors.

An SVBONY SV165 guide scope with a natively connected QHY-5II-M guide camera was used for PHD2 multistar pulse auto-guiding via the INDI server. The auto-guiding was controlled by a separate Linux laptop indoors.

This system was used to collect RAW colour data on NGC7000

System 2

Stella Mira 66 ED APO refractor

ZWO Electronic Focuser

ZWO Electronic Filter wheel

UV/IR Cut filter

SVBONY SV 605MC 14 bit Cooled, monochrome CMOS camera

SVBONY SV165 Guide scope

QHY-5II-M guide camera

MeLE Quieter 2D fanless mini PC running Fedora Linux

TP-Link LS108G 8 Port Gigabit Network Switch

Tenda P200 x 2 Powerline Ethernet adapters

JJC DHS-1 USB Lens Heater Strip x 3 (For imaging scope, guide scope and ZWO electronic focuser)

Multi USB 4 Port Plug Adaptor

5A 12V Power adapters x 3 (For EAF, Cooled CMOS camera and Lens Heater Strips)

Mains extension lead

The small headless MeLE computer is connected via Ethernet to a powerline adapter which is paired with a matching powerline adapter indoors. This link forms a reliable and encrypted Ethernet connection between the powerline adapters and thus allows the small form factor computer to be accessed by its IP address from any computer on the local network. 

AstroDMx Capture is run on the capture computer connected to the local network and can access all of the devices in a similar fashion to how they would be if they were connected directly via USB. PHD2 auto-guiding software is run on the guide computer. This constitutes a distributed system.

This system was used to collect monochrome data on M33

With both systems, Lights, Darks, Flats and Bias frames were captured.

5 minute RAW subs were captured for the colour data and 3 minute subs for the monochrome data.

To be absolutely clear; the following is not a prescriptive formula that should be followed. Rather, it is simply an example of the way that free software can be used to develop a workflow for the processing of image data from capture to final image.

NGC7000 with System 1

Software 1: ASIDeepStack

The simplicity of calibrating and stacking with ASI Studio's ASI DeepStack

 

Launch ASI Studio

Select ASIDeepStack

Notice that there are four tabs: Bias; Flat, Dark and Light

All that is needed is to select a tab, say Flats. Then drag the folder containing the Flats onto the indicated area.

The Flat tab will be populated with the Flats

Exactly the same thing is done with the Bias, Dark and Light tabs, dragging the appropriate folders to the indicated areas in each of the tabs

Clicking on the Play button in the Stack area will initiate the aligning, calibration and stacking of the Lights (image files).

When the process is finished, the stacked image is presented auto-stretched for inspection

Some limited processing can be done here which does not affect the auto-saved stacked Fits and Tiff files.

Clicking on the disk icon at the bottom will save the image as it appears as a high quality JPG. If the Noise Reduction box is checked, a denoising is applied to the image that is saved. However, it should be stressed that the auto-saved Fits and Tiff files are unaffected and are unstretched.

For some, this may be enough and a presentable image that can be shared has been saved.

The JPG saved before additional processing

The JPG saved after the additional processing

Monochrome M33 data

Similarly the monochrome data on M33 were aligned, calibrated and stacked in ASIDeepStack

The high quality JPG saved with only Noise reduction

Further processing with the other free software

This processing will be done here on the 16 bit colour Fits image of NGC7000 that was auto-saved.

Software 2: GraXpert with AI components

16 bit fits image of NGC7000 loaded into GraXpert

The image was stretched the minimum amount so that the effects of the processing could be seen.

Background extracted

AI Denoised

The stretched, denoised image with linked channels

The stretched, denoised image with unlinked channels

In this workflow GraXpert stretched images with or without linked channels will not be used; however, they do afford other ways of proceeding with the processing.

The Processed (but not the stretched) image was saved as a 16 bit Tiff file.

Software 3: Siril 

The processed image from GraXpert was loaded into Siril and Autostretch was turned on so that the image would be visible. (This does not affect the image itself, only its visualisation)

In Image Processing, Photometric Colour Calibration was selected. The object name (NGC 7000) was entered and told to find in the database. When this is done, the required information on the object populates the appropriate fields in the dialogue. Force plate solving and flip image if required were also selected.

Then OK was selected and the image was Photometrically Colour Corrected.

The image was then saved with a new name as a 16 bit Tiff file

Software 4: The Gimp 2.10 including the Starnet++ star-removing plugin.

The image was duplicated and the Starnet++ used to remove the stars after the image was converted from Perceptual gamma to Linear.

Stars removed from a duplicate of the image, and the image flattened.

Starless image pasted as a new layer onto the original starry image and subtracted, producing an image of the stars, and the image flattened.

The starless image stretched with Curves

The stretched, starless image

While still in the Gimp, the image was converted from Linear to Perceptual gamma.

Software 5: Seti Astro's Cosmic clarity AI programs

The stretched, starless image was copied into the input folder of Cosmic Clarity

The Non-Stellar sharpening selected. 

Non-Stellar Sharpening PSF left at default.

Non-Stellar Sharpening Amount set to a modest 0.65

The sharpening process in progress

The sharpened image is in the output folder of Cosmic Clarity.

The Cosmic Clarity sharpened image

A more dramatic sharpening could have been achieved by using a higher value for Non-Stellar Sharpening Amount

Back in the Gimp, the stars were replaced by pasting the stars image onto the sharpened, starless image with a combining mode of Addition (although it could have been Screen). Before the image was flattened, the saturation of the stars layer was adjusted with Hue and Saturation, and the contribution of the stars to the image was controlled by Curves. Then the image was flattened, scaled and re-oriented to a more familiar view

The final image of NGC 7000, The North America Nebula

We have shown here that Free Software (in the sense of no cost to the user) can be used successfully and flexibly to process deep sky astronomical images from capture to final image.

Further testing of the SVBONY SC715C

Solar imaging and more deep sky imaging

Solar Imaging

Clicking on any image will get a closer view.

H-alpha light

A Solarmax II 60 BF15 H-alpha scope fitted with an IR/UV cut filter and a prototype SVBONY SC715C OSC camera was mounted on a Skywatcher Solar Quest solar finding and tracking mount.

Telescope equipment

Two overlapping areas of the Sun were imaged with AstroDMx Capture by capturing 1500-frame RAW SER files

AstroDMx Capture streaming H-alpha data

The best 75% of the frames in each SER file were debayered and stacked in Autostakkert!4 The two resulting images were stitched in Microsoft ICE, wavelet processed in waveSharp and further processed in Gimp 2.10 and G’MIC-QT. 

The Sun in H-alpha light

The SC715C captured the H-alpha data very well in high detail.

White light

An Ekinox 80mm ED refractor F = 400mm with a Skywatcher auto-focuser and fitted with a Photographic grade Baader solar filter OD = 3.8, and an SVBONY SC715C OSC camera was mounted on a Skywatcher Solar Quest solar finding and tracking mount.

The scope was focused remotely with a 4tronix Focus RF auto-focuser controller.

Telescope equipment

Two overlapping areas of the Sun were imaged with AstroDMx Capture by capturing 1500-frame RAW SER files.

AstroDMx Capture streaming White light data

The best 75% of the frames in each SER file were debayered and stacked in Autostakkert!4. The two resulting images were stitched in Microsoft ICE, wavelet processed in waveSharp and further processed in Gimp 2.10. 

Note that the preview of the Sun in white light has a green hue. This is normal for true RAW data because the Bayer pattern has twice as many green pixels as either red or blue. The Bayer pattern of the SC517C is GBRG. All colour corrections are made in post processing.

The Sun in White light

Deep Sky imaging

An Altair Starwave Ascent 60 ED doublet refractor with Field flattener-reducer and a Pegasus FocusCube V2, and fitted with an Altair 2” Magnetic filter holder with an L-eNhance filter an an SC715C OSC camera, was mounted on a Celestron AVX mount. An SVBONY SV165 guide-scope fitted with a QHY-5II-M guide camera was mounted on the imaging scope. 

The mount and focuser were controlled by AstroDMx Capture via an INDI server running on the imaging computer indoors. PHD2 multi-star pulse auto-guiding was done via the INDI server on a separate Linux computer indoors.

The telescope equipment

Two hours worth of 2 minute exposures were captured of the Satellite cluster at the heart of the Rosette nebula as RAW Fits files, along with calibration frames.

The live-stacking experimental feature in AstroDMx Capture was used during image capture to improve the preview, of the image capture. 60 image light frames were captured in total.

AstroDMx Capture having captured 60 frames, showing just the 60th frame captured

AstroDMx Capture having captured 60 frames, showing the live-stack of 60 images

Clearly the preview was vastly improved by the live-stacking.

The data were debayered, calibrated, stacked and partly processed in PixInsight and further processed in GraXpert, Cosmic Clarity, Gimp, ACDsee and G'MIC. Four renderings are presented here:

The Satellite cluster and associated nebulosity

Linked channels

Unlinked channels

Blend of Linked and Unlinked channels

HOO rendering

The SC715C was able to capture high resolution data on this bright nebulosity and produced good results.

It is intended to add to this post shortly as more data become available so:

Additional testing of the SC715C

Lunar imaging

The SVBONY SC715C OSC camera fitted with a UV/IR cut filter was placed at the focus of a Skymax 127 mounted on a Celestron AVX mount. The telescope was focused remotely with a 4tronix Focus RF auto-focuser controller.

The equipment

AstroDMx Capture was used to capture RAW 1500-frame SER files of different regions of the Moon.

The best 75% of the frames in the SER files were debayered and stacked in Autostakkert!4.

The combination of small pixel size and long focal length of this system leads to oversampling. However, before the images were processed, they were re-scaled down by 66%. Microsoft ICE was used to stitch various files together to produce a larger image from which interesting areas could be cropped. The images were wavelet processed in waveSharp and further processed in Gimp 2.10 and ACDSee.

Two regions of interest:

Palus Somni, Mare Crisium, Mare Fecunditatis region

Theophilus, Cirillus, Catharina, Rupes Altai, Piccolomini region

Solar Imaging

H-alpha light

A Solarmax II 60 BF15 H-alpha scope fitted with an IR/UV cut filter and a prototype SVBONY SC715C OSC camera was mounted on a Skywatcher Solar Quest solar finding and tracking mount.

Two overlapping areas of the Sun were imaged with AstroDMx Capture by capturing 1500-frame RAW SER files

AstroDMx Capture streaming H-alpha data

The best 75% of the frames in each SER file were debayered and stacked in Autostakkert!4 The two resulting images were stitched in Microsoft ICE, wavelet processed in waveSharp and further processed in Gimp 2.10 and G’MIC-QT and ACDSee.

The Sun in H-alpha light

Deep Sky imaging

An Altair Starwave Ascent 60 ED doublet refractor with Field flattener-reducer and a Pegasus FocusCube V2, and fitted with an Altair 2” Magnetic filter holder with an L-eNhance filter and an SC715C OSC camera, was mounted on a Celestron AVX mount. An SVBONY SV165 guide-scope fitted with a QHY-5II-M guide camera was mounted on the imaging scope. 

The mount and focuser were controlled by AstroDMx Capture via an INDI server running on the imaging computer indoors. PHD2 multi-star pulse auto-guiding was done via the INDI server on a separate Linux computer indoors.

The Seagull nebula

104 minutes worth of 2 minute exposures were captured of the Seagull nebula as RAW Fits files, along with calibration frames.

The live-stacking experimental feature in AstroDMx Capture was used during image capture to improve the preview, of the image capture. 52 image light frames were captured in total.

AstroDMx Capture having captured 30 frames, showing just the 30th frame captured

AstroDMx Capture having captured 30 frames, showing the live-stack of 30 images

The data were debayered, calibrated, stacked in ASIDeepStack and further processed in GraXpert, Cosmic Clarity, Gimp, ACDsee and G'MIC. Three renderings are presented here:

RGB

HOO

Blend of RGB and HOO

Once again the SC715C was able to capture high resolution data on this nebulosity and produced good results.

A further session is required to complete this round of testing of the SVBONY SC715C OSC uncooled camera.