First Light testing of the SVBONY version of the T7 W2568A high speed astrocamera as a Linux astro-imager with AstroDMx Capture for Linux

This is a low priced astronomy camera that is a suitable introduction to astronomical imaging; not only of the Solar system but also some of the deep sky objects.
The camera is marketed as a high-speed camera and, by implication, a planetary camera.
It can be obtained from the SVBONY official AliExpress store.
I have tested the camera specifically as a Linux astronomical camera using AstroDMx Capture for Linux. The camera supplied by SVBONY was packaged well and includes a number of items.

The box contains
    • The T7 W2568A astrocamera
    • A wide angle lens
    • An auto-guiding cable
    • A USB 2.0 cable
    • An IR/UV cut filter assembly
    • An extension nose-piece
    • Two dust caps
    • A par-focal ring with three thumbscrews. place

The camera with the par-focal ring in place

The par-focal ring is of a superior design with the three thumb screws engaging on an internal O-ring so the screws don’t actually make contact with the camera (or eyepiece) body.

One of the first things to do with a camera of this design is to place a patch of insulating tape over the auto-guiding port. This will ensure that the camera USB cable is not accidentally plugged into the guiding port in the dark. Some manufacturers provide a blanking plug for this purpose but many do not.

The auto-guiding port protected by insulating tape

The substantial par-focal ring can be seen clearly with its three retaining screws.

There are very handy calibration marks on the side of the camera body, making re-positioning much easier.

Calibration marks on the camera body

The camera reports itself as a ZWOASI120MC although it contains a MT9M034 sensor rather than the AR0130CS of the ZWO. The camera will stream 8 bit images and it will stream 16 bit (12 bit in a 16 bit container) images for short exposures. The camera will not reliably deliver 16 bit long exposures. This is not a serious limitation for a camera of low cost. (Moreover, a similar issue is evident in the USB 2.0 ZWO with 16 bit long exposures if the compatibility firmware is used.) In this experiment, the standard camera firmware was used, and a Linux machine with the kernel patched to eliminate the maxpacket limitation in the USB data stream was employed. Note! with the Linux Kernel 4.16.8-300.fc28.x86_64 released by a Fedora 28 update on May 15, 2018, no kernel patch is needed. 16 bit short exposures could be advantageous with solar imaging where the capture of subtly different levels of brightness is important. With 8 bit images, 256 distinct levels of brightness can be recorded, whereas, with 12 bit output (into a 16 bit container) 4096 distinct levels of brightness can be recorded.

Deep Sky imaging

The SVBONY T7 astrocamera was placed at the Newtonian focus of an f/5, Skywatcher Explorer 130 P-DS Newtonian mounted on a Celestron AVX, EQ, GOTO mount. 30 x 20s exposures of M3 were made with real-time dark-frame correction, saving the images as TIFF files using RAW 8 capture with high quality de-bayering on the fly.

Screenshot of AstroDMx Capture for Linux streaming images of M3 without real-time dark-frame correction

Note the background noise in the displayed image.

Screenshot of AstroDMx Capture for Linux streaming images of M3 with real-time dark-frame correction

Note the removal of the background noise by the real-time dark-frame correction.

Animation alternating between the real-time dark-frame corrected and uncorrected views

The real-time dark-frame correction is ideal for outreach and ‘eyepiece sharing’ observing and imaging.
The images were stacked in Deep Sky Stacker running in Wine and post processed in The Gimp 2.10

M3

40 x 35s exposures of M104 were made with real-time dark-frame correction using AstroDMx Capture for Linux, saving the images as TIFF files using RAW 8 capture with high quality de-bayering on the fly.
The images were stacked in Deep Sky Stacker running in Wine and post processed in The Gimp 2.10 and Neat Image.

M104

Planetary imaging

The camera was then tested in its high speed planetary camera mode. The lens from a x2 Barlow was screwed onto the nose-piece of the camera which was then placed at the Cassegrain focus of a Skymax 127 Maksutov. A region of interest of 320 x 240 was selected and a 2min SER file of Jupiter was collected (under poor seeing conditions) using RAW 8 capture with high quality de-bayering on the fly. 10,000 frames were captured. The best 40% of frames were stacked in Autostakkert! 3 and wavelet processed in Registax 5.1 both running in Wine. The final image was post processed in the Gimp 2.10

Jupiter with the GRS

First impressions of the SVBONY T7 camera are that is is a very good value device, ideal  as an introductory camera for Solar System and brighter deep sky object astrophotography. It is an impressive device and has capabilities that will produce pleasing results. Depending on the exposure, with a region of interest of 230 x 240, a frame rate of up to 250fps can be achieved. It should also be noticed that relatively small aperture telescopes have been used for the current tests. Later testing will involve the use of much larger aperture telescopes.

Deep sky with a QHY 5L-ll-M and AstroDMx Capture for Linux

A Bresser Messier-AR-102-AS ED refractor was mounted on a Celestron AVX, EQ, GOTO mount. A QHY 5L-ll-M camera was placed at the prime focus. AstroDMx Capture for Linux was used to capture 16 bit FITs files with matching dark frames.
M104 ans M64 were captured with 20 x 50s exposures M3 was captured with 40 x 16s exposures.
The Fits files were stacked with dark-frame correction in Deep Sky Stacker, running in Wine. The resulting images were processed in FITs Liberator and post processed in The Gimp 2.9.
With M3, the stacked image was processed by four transformations in FITs Liberator (arcsin, root, log(root) and log(log)). The images were converted to BMPs and combined with weighting in Andrew Sprott's Flexible Image Combine (FIC).

M3

M64

M104

FULL SIZE
M3

M64

M104

Jupiter with an SVBONY SV105 camera, a Skymax 127 and AstroDMx Capture for Linux

An SVBONY SV105 camera was placed at the Cassegrain focus of a Skymax 127 Maksutov. AstroDMx Capture for Linux was used to capture a 3 min SER file of Jupiter. The best 25% of the 2292 frames captured were stacked in Autostakkert!3 and wavelet processed in Registax 5.1, both running in Wine. The final image was post processed in The Gimp 2.10. Ganymede and the Great Red Spot are both visible.

Considering the fact that the seeing was poor and the telescope only has a 5" aperture, the detail in the image is acceptable from this low cost camera.

Bug in the recent Linux kernels affecting Video 4 Linux

There is a bug that has been introduced into the Linux kernel since April 12, 2018.
The bug manifests itself as each V4L camera on the USB bus being presented twice. This is the information I have at the moments on the versions involved:
This problem has been found on Fedora kernels but may be present in other kernels.

Fedora Linux kernel version

4.15.17    Apl 12    works correctly
4.16.4      Apr 24    kernel bug displaying 2 devices
4.16.5      Apr 27    kernel bug displaying 2 devices

In AstroDMx Capture for Linux, the bug shows itself at connect time:

Screenshot of the camera connect dialogue showing the cameras presenting twice

Everything will work fine if the first instance of the device is chosen.
It should be noted that this is a bug in the Linux kernel, not in AstroDMx Capture for Linux.
The bug has been reported to the kernel developers and we shall have to see how long they take to fix it. At the moment one can solve the problem by booting into an earlier version of the kernel, or by simply choosing the first device when two are presented. Cameras that are not V4L cameras are not affected.
Nicola has implemented a workaround to eliminate this problem. It will be present in the next release of AstroDMx Capture for Linux.

The terminator of the 98.5% waxing, gibbous Moon with AstroDMx Capture, a SVBONY SV105 camera and a Bresser Messier-AR-102XS ED refractor

An SVBONY SV105 camera was fitted with a Baader green continuum filter and a x2 Barlow using the refractor at f/9. AstroDMx Capture for Linux was used to capture 4 overlapping, unsaturated, 1500 frame SER files with real-time flat-field correction of the terminator of the 98.5% waxing Moon. The best 75% of the frames in each of the SER files were stacked in Autostakkert! 3, wavelet processed in Registax 5.1 and stitched into a mosaic by Microsoft ICE, all running in Wine. The final image was post processed in the Gimp 2.9.

Using the Barlow still allowed significant oversampling with the 3 micron pixels of the SV105. The 10nm bandpass continuum filter in the middle of the visible, provided light reduction for the very sensitive camera, and eliminates any possible dispersion, notwithstanding the ED objective of the telescope

Modifying a Celestron Omni XLT 150 Newtonian for using a light pollution (or other) filter when a DSLR is directly connected to the telescope.

The Omni XLT 150 f/5 Newtonian, shares a problem with a number of other Newtonians in that when a DSLR camera is connected to the focuser via a 1.25" adapter, the scope does not have enough back focus to allow the image to be brought to focus.
The solutions to this problem have been:

• Use a Barlow lens to increase the focal length of the system. This allows focus to be achieved, but at the expense of brightness of the image and field of view.
• Move the position of the mirror further up the tube. This is a drastic solution, and is particularly difficult with the Omni XLT 150.
• To use the direct camera connect threads on the focuser that allow a camera T-ring to be screwed to the end of the focuser tube. This has the advantage of allowing the camera to be brought to focus. Another, important consequence of using the direct connection method is that the camera cannot fall out of the focuser as could happen with a 1.25" adapter, if the tightening screws have become loose. Moreover, with direct attachment, there is less potential for vignetting. However, there is a huge disadvantage to the direct attachment method: it is not possible to use a light pollution filter, which makes a critical difference if the sky suffers from even slight light pollution. Moreover, if the user wishes to use any other filter, the same problem arises.
• There are also, some astronomy cameras that do not have a filter-threaded nose piece. With some scopes this is not a problem because a threaded extender tube can be used. However, with many Newtonians this is not possible because the camera is now held too far out to achieve focus.

We show here, an experimental method of allowing a 1.25" light pollution filter to be used with direct camera connection. This is a solution that could be adopted by Celestron (or any other manufacturer) at very little cost, as a standard component of the focuser.

First, a Barlow lens was disassembled so that the middle tube, which is filter threaded, could be removed and used as an internal filter holder in the focuser tube.

A thin shim of plastic tape was placed around the middle tube and it was inserted tightly into the focuser tube and fixed in place with superglue.

The filter threaded Barlow tube was pushed far enough into the tube to allow the 1.25" adapter to be screwed back into place for normal eyepiece work. This adapter has to be removed for filter insertion and direct camera attachment.

After removal of the 1.25" adapter, the Light Pollution filter can be screwed into the Barlow tube threads.

The T-ring can then be attached as usual, ready for direct camera attachment.

Or the 1.25" adapter can be replaced, with the filter in place, for use with a camera that does not have a filter thread as in a camera tested recently.

It is unlikely that this procedure will introduce any more vignetting into the image than would have been produced if the scope had enough back focus to allow a 1.25" adapter to have been used.

In my view, any scope with the facility to attach a DSLR directly to the focuser, should have a filter threaded section inside the focuser to allow the use of filters, in particular, light pollution filters.

FITs files, AstroDMx Capture for Linux and a Bresser Messier AR-102XS ED, f/4.5 refractor,

Nicola has implemented FITs files in AstroDMx Capture for Linux. These are the first tests of this implementation.

A Bresser Messier AR-102XS ED, f/4.5 refractor, was mounted on a Celestron AVX, EQ, GOTO mount. A  QHY5L-ll-M camera was mounted at the prime focus and AstroDMx Capture for Linux, running on a Fedora laptop was used to capture Fits files with matching dark-frames. The FITs files were stacked in Deep Sky Stacker 4.1 running in Wine 3.5 and post processed in the Gimp 2.9.

Click on an image to get a closer view.

M65 and M66 in Leo, M51 in Ursa Major and M3 in Bootes were the objects imaged. 16 bit FITs images were captured throughout (12 bit images in a 16 bit FITs container).

20 x 30s exposures were captured of M65 and M66. 

30 x 45s exposures were captured of M51 

50 x 5s exposures were captured of M3.

A new release will be made when Nicola has added more functionality to the filter-wheel controls.

Experiments with a low cost SVBONY SV105 camera and AstroDMx Capture for Linux

The SVBONY SV105 camera is very sensitive and a ND13 filter was attached to an extender tube attached to the camera. In all experiments, unsaturated data were collected.

This allowed the diagonal to be removed, and the camera directly attached to the focusing tube of a Bresser Messier AR-102XS, f/4.5, 102mm, ED refractor.

AstroDMx Capture for Linux was used to capture an unsaturated, 2000 frame SER file of the 9.4% crescent Moon. All of the data were collected unsaturated in the following tests.

Screenshot of AsroDMx Capture for Linux capturing the SER file

The best 75% of the frames in the SER file were stacked in Emil Kraaikamp's Autostakkert! 3.1.0 currently under beta testing. Running in Wine 3.5 on a Fedora Linux laptop.

The resulting image was wavelet processed in Registax 5.1 also running in Wine and post processed in the Gimp 2.9.

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Another test was made using a Skymax 127 Maksutov

The SVBONY SV105 camera was fitted with an extension tube with a ND13 filter. (the extension tube was needed because the camera nose-piece is not threaded to take a filter.) The camera assembly was attached to a Skymax 127 Maxutov mounted on a Celestron AVX, EQ, GOTO mount. AstroDMx Capture for Linux was used to capture a 2000 frame SER file of the Mare Crisium region of the 17.2%, waxing, crescent Moon. The best 75% of the frames in the SER file were stacked in the beta version of Autostakkert! 3.1.0 running in Wine 3.5. The resulting image was wavelet processed in Registax 5.1 also running in Wine and post processed in the Gimp 2.9.

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A third test was made using a Newtonian modified to hold a filter in the focuser tube.
A Celestron Omni SLT 150mm, f/5 Newtonian was mounted on a Celestron AVX, EQ, GOTO mount. An SVBONY £35 SV105 camera was placed at the Newtonian focus and a ND13 filter was used. AstroDMx Capture for Linux was used to capture 1500 frame SER files of three overlapping panes of the Moon, with real-time flatfield correction. The best 80% of frames of each SER file were stacked in the beta version of Autostakkert! 3.1.0. running in Wine. The images were stitched together in Microsoft ICE running in Wine and the final image was wavelet processed in Registax 5.1 also running in Wine. The final image was post processed in the Gimp 2.9.

Screenshot of AstroDMx Capture for Linux capturing a SER file of part of the Moon

Final mosaic

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A fourth test was done with the Bresser Messier AR-102XS ED, f/4.5 refractor
The Bresser Messier AR-102XS ED, f/4.5 refractor, was mounted on a Star Discovery AZ GOTO mount. An SVBONY SV105 camera was attached to an extension tube with a Baader green continuum filter fitted, and it was placed at the prime focus of the refractor.
AstroDMx Capture for Linux was used to capture a 1000 frame SER file of the Moon using real-time Flat-field correction.

Screenshot of AstroDMx Capture for Linux capturing the SER file

The best 90% of the frames in the SER file were stacked inthe beta version of Astrostakkert! 3.1.0 running in Wine 3.5. The resulting image was wavelet processed in Registax 5.1 also running in Wine and the final image was post processed in the Gimp 2.9.

The use of the Baader 1.25" Solar Continuum Filter, 10nm bandpass, centred on 540nm, served to reduce the amount of light (because the camera is very light sensitive and requires filtration in order not to saturate the sensor). Moreover, because the light is almost monochromatic, there are no dispersion effects in a refractor, notwithstanding the fact that an ED refractor was used in this experiment.

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Testing the low cost SVBONY SV105 camera with AstroDMx Capture for Linux

The SVBONY SV105 camera was purchased from the SVBONY store on AliExpress for £36. Delivery was fast, taking about a week and the tracking information was first rate.
The camera comes well boxed

The camera is supplied with a USB cable and a dust cap for the front of the built in telescope adapter.
The camera is very well built with a metal housing.

The inside of the camera is sealed by a built in optical window and it is recommended not to unscrew the adapter and allow air inside.

The sensor is a 1/3" 2Mpixel (1920 x 1080) colour CMOS OV2710 sensor with 3µm x 3µm pixels. The camera consumes 150mA at 5volts.

Initial tests have been done in daylight. and the first thing to notice is that the camera suffers from the reverse pixel vignetting that we have discussed in relation to other cameras, but which can be rectified by flat-field correction.

An average flat field was produced using AstroDMx Capture for Linux.

The reverse vignetting is clearly evident, with the lighter regions being around the periphery of the image.
This is the log file for the production of the average flat field frame by AstroDMx Capture for Linux

 AstroDMx Capture for Linux was used with real-time flat-field correction and this demonstrates that the flat-field correction rectifies the reverse pixel-vignetting.

Animation showing the correction of the reverse vignetting

The image is of an area on the other side of the valley, taken through an 80mm ED refractor.

The camera only produces output in Motion Jpeg format, but AstroDMx Capture for Linux extracts data from the video stream at the highest possible quality, so any possible problems are minimised. We have discussed Motion Jpeg in a previous post, and it is possibly the best mode of compression if any compression is imposed on the video stream. This is because each frame is separately compressed, with no reference to the contents of other frames. In an image with lots of detail, the Jpeg compression should be minimal. It is best to have no compression for astronomical imaging.

This is how the SVBONY SV105 camera presents itself with the Terminal command
 v4l2-ctl --all -d /dev/video1

...
As a separate bit of news: Nicola has now implemented FITs file capture in AstroDMx Capture for Linux. The software can now capture:

• Greyscale FITs
• Separate FITs files for each colour channel
• Genuine colour FITs images with all of the colour channels in a single FITs file

Nicola will shortly be releasing another version of AstroDMx Capture for Linux incorporating the FITs capture.

A new release of AstroDMx Capture for Linux

Nicola has released a new version of AstroDMx Capture for Linux.

http://www.linux-astro-imaging.uk/

Changelog (version 0.10.2.0)

Full support for the QHY-5L-II MONO
Full support for the QHY-5L-II COLOUR
Other QHY cameras should work but have not been tested
Histogram Added. The histogram supports both Linear and Logarithmic scales and shows channels in RGB combined, Luminance, RGB Average, Red, Green, Blue or Greyscale.
Histogram image saved as a TIFF file
Automatic Exposure, Automatic Gain and Automatic White Balance improvements (If supported by camera)
Frame integration now works for all cameras operating in 8-bit modes
Improvements to the camera log file
Improvements to the over-exposure markers
Over-exposure markers now have a sensitivity control
Improvements to the Reticle
Custom colours not allowed for the over-exposure markers and the reticle
Right-click to reset controls now works for the exposure control
Reset all controls implemented
Long exposure countdown indicator improvements
Long exposures are now cancelled before the new exposure is set
Installers now create menus to launch the software
Detailed debugging mode added - which can be invoked from the menus or manually by passing -D to the astrodmx binary
Bug fixes and other improvements

Release 0.10.2.0 has full support for:

Astronomy cameras
QHY 5L-II-M (USB2.0, 12 bit ADC)
QHY 5L-II-C  (USB2.0, 12 bit ADC)
DMK 21AU04.AS (8 bit ADC)
DFK 21AU04.AS (8 bit ADC)
DBK 21AU04.AS (8 bit ADC)
ZWO ASI120MC (USB2.0, 12 bit ADC)
ZWO ASI120MC-S (USB3.0, 12 bit ADC)
ZWO ASI120MM-S (USB3.0, 12 bit ADC)
ZWO ASI178MC (USB3.0, 14 bit ADC)
SVBONY T7 W2568A High-speed camera (USB2.0, 12 bit ADC)
Bresser MicrOcular Full HD Digital Camera (8 bit ADC)
SVBONY SV105 HD (8 bit ADC)
Orion Starshoot Solar System Color Imager IV
Altair (Orion Starshoot USB eyepiece) (USB2.0, 8 bit ADC)
USB cameras
ELP 1.3Mp CMOS board-level HD USB camera (8 bit ADC)
Lucky Zoom 5Mp microscope USB CMOS camera (8 bit ADC)
Vimicro USB2.0 UVC PC camera (e.g. Maplin USB2.0 Microscope) (8 bit ADC)
USB Capture cards
KWORLD DVD MAKER 2 (8 bit ADC)
UVC capture card (Motion-JPEG only) (8 bit ADC)
EasyCAP (Motion-JPEG only) (8 bit ADC)
USB webcams
Sweex WC066 HD webcam (8 bit ADC)
Sweex WC070 ViewPlus (8 bit ADC)
Sweex WC035V2 VGA webcam (8 bit ADC)
Philips SPC900NC including SPC800 and Philips 740 flashed to SPC900NC (8 bit ADC)
Philips 690 Vesta Pro Webcam (8 bit ADC)
Logitech HD C525 (8 bit ADC)
Microsoft LIFECAM 2 (8 bit ADC)
Creative Webcam Live (8 bit ADC) Bayer output only.
All Video 4 Linux cameras.
ZWO filter wheel

Nicola is now working on implementing FITs files and the Atik 314L CCD camera

Watch this space!

More tests with the low cost Sweex WC035V2 webcam

A Sweex WC035V2  VGA CMOS webcam costing less than £8 on Amazon UK was fitted with an IR/UV cut filter and placed at the Cassegrain focus of a Skymax 127 Maksutov. The scope was mounted on a Celestron AVX, EQ, GOTO mount. AstroDMx Capture for Linux, running on a Fedora laptop was used to capture 2000 frame SER files of various regions of the 63.4% waxing, gibbous Moon. The best 90% of frames in the SER files were stacked in Autostakkert! 3 and the resulting images were wavelet processed in Registax 5.1, both running in Wine. Microsoft ICE was used to stitch together two overlapping images in the Tycho, Clavius region.

Sweex WC035V2 camera

Screenshot of AstroDMx Capture for Linux, capturing a SER file

Composite of two overlapping panes showing craters Clavius, Gruemberger, Morteus, Maginus and Tycho

Eratosthenes, Mons Wolff and Montes Apenninus

Archimedes, Autolycus and Aristillus

There were some slight compression artifacts, but not enough to spoil the results from this very low cost webcam. The camera also gave very pleasing live views that would be very suitable for outreach work.

It is likely that Nicola will release the next version of AstroDMx Capture for Linux later today.