Monday, 16 July 2018

Slight delay in the release of the next version of AstroDMx Capture for Linux


Nicola is making great progress with the implementation of the Atik 314L in AstroDMx Capture for Linux as previous posts have shown. However, she has also been trying to resolve a problem over the QHY cameras giving unreliable exposures at certain long exposures. This is a problem with the QHY SDK.

The problems have been reported and new SDKs have been released. However, with each new SDK release, a number of other serious, deal-breaker problems have been introduced. These in turn are being reported, and the hope is that the QHY SDK developers will soon resolve all of the problems. In the meantime, it may be necessary to produce a release of AstroDMx Capture for Linux that implements the Atik 314L (and possibly others) before the QHY issues are resolved.

This is unfortunate and disappointing, but it is important to realise that the problem is not with the AstroDMx Capture code, but rather, with the SDK that has to be used to call the camera functions.

I will make sure that when a new release is made, the information will be posted here. Nicola will implement a hack that should improve the exposure situation for the QHY, but that is no substitute for a reliable SDK.

Sunday, 15 July 2018

Testing a new display function in AstroDMx Capture for Linux with an Atik 314L camera

An Atik 314L camera was placed at the Newtonian focus of a Skywatcher 130 PDS 130mm, f/5 Newtonian, mounted on a Celestron AVX GOTO mount. 16 x 48s exposures were captured of M8, the Lagoon nebula and 5 matching dark-frames using AstroDMx Capture for Linux. The images were dark-frame corrected and stacked in Deep Sky Stacker running in Wine. The final image was processed in Fits Liberator, running in Wine and the Gimp 2.10.

The problem with 16 bit imaging is that the image being captured has to be rendered in 8 bits so that it can be viewed on the computer screen. Moreover, the interesting parts of the data are very dim and with a simple scaling of the results to 8 bits, much of the object being image will probably be invisible. What is needed are transfer functions that will brighten, in a non-linear fashion, the image data, so that the fainter parts of the object are revealed. These transformations are only made to the displayed image, leaving the saved data untouched. AstroDMx Capture for Linux has been given a number of controls to optimise the visualisation of the data being captured. Here we were testing a gammalog display function to help reveal the object whilst being captured.

Final image of M8, the Lagoon Nebula



The images were captured while testing the new gammalog image display function in AstroDMx Capture for Linux.
Sreenshot

The preview image can be brightened or dimmed using the other non-destructive controls of gamma, brightness and contrast.
Additional display transformation functions are being implemented now and will be tested as soon as possible.

Tuesday, 10 July 2018

Occultation disks and streetlights

To the astronomical imager, streetlights can be such a problem as to make imaging all but impossible. I don't mean the general problem of light pollution in the sky caused by streetlights, I mean the glare from nearby streetlights that can shine directly into the telescope and ruin any results.
We have a streetlight right outside the front of the house. The council fitted internal baffles to the lamp on request, which reduced it in brightness a little, but it is still able to cast its bean of light onto our scopes that we have to use at the front of the house in order to image objects lower in the sky. This problem is solved by mounting a blackened occultation board on a sturdy tripod and placing it so that it casts its shadow onto the scope. This solution works very well and occultation disks or boards can help problems with more distant street lights that are in the general direction of where the scope is to be pointed.

The streetlight can be seen very close beyond the occultation board.


From the point of view of the scope, the street light is completely obscured and does not cause a problem.
Smaller occultation boards, strategicall placed, can deal with problems caused by more distant lights.

Saturday, 7 July 2018

First Light for the Atik 314L implementation in AstroDMx Capture for Linux

An Atik 314L camera was placed at the Newtonian focus of a Skywatcher 130PDS, 130mm, f/5 Newtonian, mounted on a Celestron AVX, EQ, GOTO mount. 16 bit Fits images were captured of  M16 (40s), M17 (40s) and M13 (35s) using AstroDMx Capture for Linux. For each object, the best 26 frames were stacked in Deep Sky Stacker, running in Wine. The images were post-processed in Fitswork (running in Wine), The Gimp 2.10, RawTherapee and Neat Image.

M16 the Eagle nebula and cluster

The Pillars of Creation

M17, the Swan or Omega nebula

M13

 Nicola hasn't quite finished the Atik 314L implementation. When it is finished, it will be present in the next release; which has been delayed by problems with the latest QHY SDK. QHY have been made aware of the problem and are currently working on it. In the meantime, the Atik 314L implementation goes ahead.

Tuesday, 19 June 2018

Adjusting the azimuth clutch on a Skywatcher Star Discovery mount.

Unlike the Synscan AZ, GOTO mounts, the Star Discovery Mount has FreedomFind™ dual encoder technology. This allows the mount to be pushed manually in either axis during use, and the controller keeps track of where the mount is pointing. The altitude axis has a sturdy clutch release and adjuster. However, the azimuth axis does not. With use, it is commonly found that the azimuth clutch becomes slack and the mount can be turned manually too easily. Even a gust of wind might be able to turn the scope on the azimuth axis.

Four screws hold the plastic top on the mount. When this is removed the double clutch assembly is exposed. The bottom clutch controls how difficult it is to manually turn the azimuth axis.

A spanner was made by hammering and filing a tool that came with a self assembly item, until it was wide enough to slide onto the flats on the bottom clutch. There are two Allen-key grub-screws between the flats opposite each other and these are slackened off with an Allen key. The clutch is then turned a very tiny amount clockwise and the grub screws tightened.
It is clearly a matter of trial and error to get the adjustment right, but this procedure works. It is best to turn the clutch by an almost imperceptible amount at one go. If it is overtightened, then the mount will stall while slewing in certain directions due to some asymmetry within the system.

Manufactured spanner and Allen-Key



The spanner engaging the flats

One of the retaining grub-screws is visible
I don’t know whether this procedure will invalidate the warranty, but I found that without doing it, the mount was virtually unusable. Nowhere in the manual is it explained how to correct this problem.

I use this mount as a substantial, quick setup, AZ GOTO mount for Solar system and deep sky observing and imaging. Previous postings on this blog show the mount in action. Of course there is image rotation, but as long as there is no perceptible rotation within images, then Deep Sky Stacker and lxnstack for example, are able to de-rotate the images during stacking. Keeping the azimuth clutch adjusted correctly is going to be critical for the continued use of this mount.

Monday, 11 June 2018

M17 with AstroDMx Capture for Linux and a QHY 5-II-M

An f/5, Skywatcher Explorer 130 P-DS Newtonian Was mounted on a Celestron AVX, EQ, GOTO mount. A QHY 5-II-M camera was placed at the Newtonian focus and AstroDMx Capture for Linux was used to capture 40 x 25s exposures of M17, the Omega or Swan Nebula as Tiff files. Matching dark-frames were captured. The frames were stacked in Deep Sky Stacker running in wine and the resulting Fits file was processed in the ESO, ESA, NASA FITS Liberator 3 software running in Wine. The resulting Tiff file was processed in Neat Image V8 and RawTherapee.

FITS Liberator
FITS Liberator is a very good program for non-linear stretching of Fits Images

M17

Full Size


Wednesday, 30 May 2018

Nature study with AstroDMx Capture for Linux

A Zoom TV lens was fitted to a DFK mounted on a small tripod and the camera was aimed at an active bird nesting box.

DFK with a zoom TV lens

AstroDMx Capture was used to capture a SER file of the nesting box.

Te Debian laptop capturing data


Screenshot of AstroDMx Capture for Linux capturing data


SER player was used to cut out the frames containing action. A SER file and AVI were made as high quality recordings and an animated GIF was made to show the results here on the blog.

Animated GIF

Full size

The software has the capacity for time-lapse imaging down to 0.1s intervals, but for the fast flight of the blue-tits, a 30fps SER file was the best way to capture the data

Saturday, 26 May 2018

ChromeOS, Android and the SVBONY SV105 camera

There are two operating systems based on the Linux kernel that are not usually thought of as Linux. This is because, whilst they are both based on the Linux kernel, they are both, by design, unable to run Linux desktop applications. With ChromeOS, most of the applications run in the Chrome browser environment. In Android, a whole ecosystem of applications run in the Android environment, and cannot be run on a normal Linux desktop.

ChromeOS
The low cost SVBONY SV105 camera and a Chromebook.

There is no good imaging software for ChromeOS, however, there is a simple camera application that can be used in camera auto mode, and is suitable for outreach. It is even possible to grab images. Here is the setup with a Samsung Chromebook and SVBONY SV105 with a Skymax 127 on an iOptron AZ, GOTO mount, along with an image grabbed by the camera application.
Click on an image to get a closer view.

The Setup with scope, camera and Chromebook

An image captured by the camera software


Android
The SVBONY SV105 camera and Android:
The SV105 comes with a 1.8m USB cable which has a short fly-out USB lead to provide extra power to the device which has a power consumption of 150mA at 5volts. This was essential for using the camera with a Samsung 10.1 inch Galaxy Note tablet. The tablet was not able to supply sufficient power to operate the camera. A 5v 2.1A mobile phone portable charging device was used as an auxiliary power supply, connected via the fly-out lead. A powered USB hub could be used alternatively to provide extra power. My Samsung tablet was temperamental so far as detecting the camera, possibly because it is quite an old device. It helped to have the device fully charged.

Auxiliary power supply

The SV105 camera was placed at the Cassegrain focus of a Skymax 127 Maksutov and was connected to the Android tablet computer.
There is, available in the Google Play store, a USB camera capture application called USB Camera. This is a particularly good application because it presents the main controls of the camera, enabling the correct exposure etc. to be set. It works with UVC cameras.

Photograph of Android tablet streaming images from the SVBONY SV105 camera


Screenshot of USB Camera streaming video

USB Camera can capture mp4 Movies or still images.

Controls for Video formats


A drop-down menu allows the selection of the camera controls which can be hidden.
Drop down menu for camera controls


Single captured image


The combination of the SV105, Android and USB Capture provides a very credible observing, eyepiece sharing and even imaging platform.

At the moment, Android seems to be the superior of the two platforms for astronomical viewing and imaging, with one caveat; that the aging tablet used for these experiments was temperamental, even with an auxiliary power supply, with respect to detecting the camera (any camera). However, once detected, everything worked fine.
There are available Android notebooks, and depending on the version of Android they are running, they could be more suitable devices than a tablet (or phone), if they can run the capture software.
The weakness of ChromeOS is the lack of suitable capture applications.
Both platforms would benefit from the development of applications that are capable of capturing movies in the SER format, a superior format for astronomical imaging. This would produce data that could be transferred to another computer for processing.

Thursday, 24 May 2018

High Definition Lunar image with SVBONY T7 W2568A camera and AstroDMx Capture for Linux

A low-cost SVBONY T7 W2568 high speed camera was placed at the Cassegrain focus of a Skymax 127 Maksutov mounted on a Celestron AVX, EQ GOTO mount. 3000 frame 8 bit SER files were captured of 4 largely overlapping regions on the terminator in the Clavius Tycho region using AstroDMx Capture for Linux. The best 50% of the frames in each of the SER files were stacked in Autostakkert!3 running in Wine and the 4 panes were stitched into a mosaic using Microsoft ICE also running in Wine. The mosaic image was wavelet processed in Registax 5.1 running in Wine. The final image was post processed in the Gimp 2.10 and RawTherapee.

















Full Size


This low cost camera is definitely worth having for this kind on high definition work.

Monday, 21 May 2018

Deep Sky with the SVBONY T7 W2568A camera, AstroDMx Capture for Linux and a 10 inch, f/4.8 Newtonian

An SVBONY T7 W2568A camera was placed at the Newtonian focus of an Orion Europa, 10 inch, f/4.8 Newtonian. Exposures were captured in RAW 8, with real-time dark-frame and flat-field correction using AstroDMx Capture for Linux on a Debian laptop. The exposures were saved as Tiff files. M13 (50 x 15s exposures), M57 (30 x 45s exposures) and M82 (30 x 60s exposures). The exposures were stacked in Deep Sky Stacker running in Wine and Post processed in the Gimp 2.9 and Neat Image.



M82







Screenshot of AstroDMx Capture for Linux capturing M82 data with real-time dark-frame and flat-field correction


M57


M13

Quite acceptable deep-sky images from this low cost SVBONY W2568A high-speed camera. An ideal starter camera.

Sunday, 20 May 2018

High resolution Lunar imaging with an SVBONY T7 W2568A high speed camera, a 10" Newtonian and AstroDMx Capture for Linux

An SVBONY T7 W2568A high speed camera was placed at the Newtonian Focus of an Orion, 10 inch, f/4.8 Newtonian. AstroDMx Capture for Linux running on a Debian Linux laptop, was used to capture 6 overlapping, 1500 frame SER files of the 24.8% waxing, crescent Moon. The best 50% of the frames in each SER file were stacked in Autostakkert! 3 and stitched together into a single image with Microsoft ICE both running in Wine. The resulting image was wavelet processed in Registax 5.1. also running in Wine. The final image was post processed in the Gimp 2.9.

24.8% waxing, crescent Moon


The SVBONY T7 high speed camera can produce High resolution images worthy of more expensive devices.

Saturday, 19 May 2018

ZWO Gamma Gone! but not quite!

Gamma has been removed from the ZWO SDK!

This means that ZWO cameras will no longer provide a control for gamma.
At first sight this might seem like a strange thing to do, but in reality, it is not.
There is a powerful argument that image processing should be done after the data have been captured.

In general, image processing involves the selective discarding of information in the image data in the effort to recover as much information about the underlying structure of the image, such as the bands on Jupiter, or the arms of a spiral galaxy. If any of the information is discarded at capture time, it is lost forever, whilst if it is discarded post capture, it is still available in the original image data.

Gamma is such a function that involves the selective changing of the mid-range values of the brightness of an image, whilst leaving the darkest and the lightest values untouched. Many cameras allow the control of gamma at capture time, as it can produce a more pleasing view of the subject being captured. However, it must never be forgotten that the brightness values that are changed (and thus lost) will not be available in the captured data.

Experienced planetary imagers such as Christopher Go, eschew the control of gamma at capture time. What is important is to get the exposure, including gain, right at capture time. Some advanced imaging cameras only allow the control of exposure and these are often true 16 bit devices.

In order to mitigate this loss of control over gamma, Nicola has incorporated gamma control in software, in AstroDMx Capture for Linux. In addition to gamma, she has also implemented contrast and brightness in software. This allows the user to control and see a pleasing view of the subject being imaged as usual. However, the changes are not propagated through to the saved image. This means that no information is discarded at capture time and is therefore available for extraction during post processing in software such as the Gimp 2.10.

For many users, this is a paradigm shift that will require a little getting used to. However, it is likely to lead to better results in the long run.

These changes are implemented in the next release of AstroDMx Capture and have been responsible for the slight delay in release. However, the gamma camera control will be retained in addition to the implementation of the software, non destructive controls.

Monday, 14 May 2018

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.

Monday, 7 May 2018

Deep sky with a QHY 5-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 5-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


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M3

M64

M104