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

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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.