The Forsaken nebula IC5068 in Cygnus

45 minutes worth of 5 minute exposures of the Forsaken nebula were captured with AstroDMx Capture through a William Optics 81 mm ED APO refractor with an Altair Hypercam 533C 14 bit OSC CMOS camera with an Altair quadband filter.

The data were debayered, calibrated, stacked and SpectroPhotometric Color Corrected and stars removed in PixInsight; post processed in the Gimp 2.10, Background extraction and stretched with linked an unlinked channels in GraXpert and SetiAstro's Cosmic Clarity sharpening and final denoising.

RGB images

Stretched with channels linked

Stretched with channels unlinked

Blend of linked an unlinked

Enhancing details in Deep sky images using GREYC's Magic for Image Computing G'MIC

There are a number of programs that can be used to enhance the details in deep sky images such as Seti Astro's Cosmic Clarity.

However GREYC's Magic for Image Computing from the GREYC research laboratory, a joint research unit of CNRS, ENSICAEN, and the University of Caen, France can be used to good effect. It has 625 filters and we are going to look a four of them here in the context of details enhancement.

Click on an image to get a closer view

The image we will use is a starless image of the Andromeda Galaxy

Starless Andromeda Galaxy

The four filters we shall use are found in the filter section Details. The names of the filters are:

• Freaky Details
• Local Contrast Enhancement
• Magic Details
• Mighty Details

We shall show screenshots of G'MIC with each filter and the preview turned on and off (to see the effect) and then the starless image processed with that filter.

The parameter settings that have been used can be seen in the screenshots, but it is important to experiment with the settings as the values used may not be optimal.

Freaky Details

Preview off

Preview on

Image processed with Freaky Details

Local Contrast Enhancement

Preview off

Preview on

Image processed with Local Contrast Enhancement

Magic Details

Preview off

Preview on

Image processed with Magic Details

Mighty Details

Preview off

Preview on

Image processed with Mighty Details

The 4 processed images were then blended 25% each in the Gimp to produce a details enhanced image with an equal contribution from each filter.

Blended image

Original image for comparison

Animation showing the results of the various G'MIC filters of the details

Animation showing the original image and the image produced by the blended G'MIC filters

In future articles we shall look at other filters in GREYC's Magic for Image Computing G'MIC for deep sky image processing.

Removal of Hot Pixels from Deep Sky images

Hot pixels in images from a colour astronomical camera appear as bright, fixed spots of red, green, or blue in deep sky astronomical images. These spots are caused by individual pixels on the camera's sensor that retain a higher-than-average charge, even in the absence of light. This excess charge manifests as a bright spot in the image.

Causes of Hot Pixels:

Sensor Defects: Hot pixels are inherent defects in the camera sensor. They are more noticeable in long-exposure astrophotography because the sensor is exposed to light for extended periods.

Cosmic rays: When a cosmic ray strikes a pixel on the sensor, it can ionize atoms within the silicon, creating electron-hole pairs. These excess charge carriers can become trapped in the pixel's structure, causing it to retain a higher-than-normal charge even in the absence of light. This trapped charge manifests as a persistent bright spot, or a permanent hot pixel.

Age: As the camera sensor ages, the number of hot pixels can increase.

Dark frame calibration should remove most or all of the hot pixels but this may not occur satisfactorily.

For one reason or another an imager might end up with hot pixels in her/his deep sky image

In the current case, the powerful open source software G’MIC Qt will be used to remove the hot pixels from the image.

G'MIC (GREYC's Magic for Image Computing) is a comprehensive open-source framework for image processing. It offers a variety of tools and interfaces for manipulating and processing images. G'MIC provides a number of user interfaces, including a command-line tool, a GIMP plug-in, a web service, and a Qt-based interface. G'MIC-Qt is compatible with several image editing programs, including GIMP, Krita, Photoshop, Affinity Photo, PaintShop Pro, and Paint.NET. It can also be used as a standalone application. G'MIC is developed in Caen, France, by the IMAGE team at the GREYC research laboratory, which is a joint research unit of CNRS, ENSICAEN, and the University of Caen. Since its inception in 2008, the development of G'MIC has resulted in numerous academic research articles focused on the design of new image processing algorithms.

Here the stand alone version is used in a Linux environment, but looks and behaves just like the Gimp plugin.

100% zoomed of part of a deep sky image showing bright red, green and blue hot pixels

Click on an image to see a closer view with more details

To remove hot pixels the Repair group of filters in G’MIC is selected and from within that group, Remove Hot Pixels is selected.

Remove Hot Pixels parameters set to mask size 5 and Threshold 4

The hot pixels have been removed.

Of course, it is advisable to experiment with the values of the filters’ parameters used to evaluate the results in each case.

A second filter called Recursive Median is capable of removing hot pixels and is selected from within the Repair group of filters.

Parameters set to Median Radius 3 and Repeats 7

The hot pixels have been removed.

Although either of these methods would suffice, doing them both and 50% blending the results in the Gimp may be preferable.

Blended of images with hot pixels removed by both filters

Animation showing the hot pixel removal by G'MIC

G'MIC Online web service interface 

GREYC's Magic for Image Computing is extremely powerful and in a separate article I shall discuss other aspects of deep sky image enhancement using this software.

Starfixer: an online tool for star reduction, the correction of elongated stars and noise reduction.

From time to time I like to try out software that I come across that makes use of AI and has the potential for inclusion in my astronomical image processing workflow. StarFixer is a Deep Artificial Neural Network, trained to detect and fix elongated stars in astronomical images, it also reduces the sizes of stars. Starfixer can produce a processed image up to 4000x4000 pixels whilst preserving its aspect ratio. Within the past few days, a denoising funtionality has been added to Starfixer.

The Starfixer project dates back to 2020 and has steadily progressed to the present day.

The developer, Filippo, a 39 years old Italian (at the time of writing), is a computer engineer with a passion for artificial intelligence and astrophotography. He began studying AI when it was (in his own words) still considered futuristic and primarily for nerds.

Starfixer is quite responsive with a simple to use web interface. An image (in png (8 or 16 bit) or jpg format) is uploaded to the system. A link to the results page is provided. The speed of the process depends on the dimensions of the image. The results page has to be refreshed manually and when the processing is complete, the results from three models V1, V2 and V3 are provided to be seen in separate tabs as well as denoising results that are discussed below. You can examine and download any or all of the the three results as a png file. At the moment, whether the input image is 8 bit or 16 bit, the output image is 8 bit. Filippo tells me that he is working on full 16 bit compatibility.

Starfixer is freeware/donationware which is a form that I prefer. Donating the price of a cup of coffee now and again is a good way of supporting the project as well as keeping Filippo awake during the long coding nights.

A series of animations of before and after Starfixing images.

The propeller nebula with elongated stars. 

The elongated stars are also reduced

The Soap Bubble nebula showing star reduction

Reducing the stars gives more emphasis to the Soap bubble nebula.

The cloud Sculpting Cluster NGC 6823 and the nebula NGC 6820

A very busy, star-rich field where the stars obscure the nebulosity to an extent. Reduction of the stars reveals more of the structure of the nebulosity.

Testing the denoising functionality of Starfixer 

The test image is a SeestaS50 image comprising a 2 minute stack of 10s exposures. The stars are clear but the image is noisy.

When an image is uploaded to Starfixer at the moment; when processing is completed, the results page contains these options for viewing the results:

Animation of the original image, The original image denoised and the AI version 3 and denoised image

FULL SIZE ANIMATION

This image did not require star reduction therefore it is important that a denoised original image is provided as well.

A 17 minutes worth of 10s exposure image of M33 captured with a Seestar S50, stacked, debayered, SPCC and ADBE processed in PixInsight, stretched in GraXpert and Gimp, was submitted to Starfixer to examine its image denoising.

Animation of the original image of M33 and the Original denoised in Starfixer

FULL SIZE

Starfixer is a welcome addition to my suite of image processing tools. The enthusiasm of the Developer, Filippo will ensure that the software continues to improve over time and will be well worth trying as another option for any astroimager.

Starfixer can be accessed at starfixer dot org

CaK solar experiment with a Seestar S50

The equipment used

Baader solar filter OD 3.8 was placed at the end of a dewshield for the Seestar S50 and held in place with glue and plastic adhesive tape.

A filter holder for the Seestar S50 with a 2” to 1.25” filter adapter.

The solar filter assembly and the adapter fitted with a Baader Ca K-line double stacked filter 394 nm peak transmission with an 8nm bandpass.

The whole assembly viewed from the bottom.

The Ca K-line filter can be seen in place.

The whole assembly seen from the top.

The Seestar S50 with the Double filter assembly in place

There were initially two unknowns in this experiment:

1) Whether a 1.25” filter would cause vignetting

2) Whether the built-in UV/IR cut filter would be so aggressive that it would prevent the Ca K-line light from being detected by the sensor.

Optical density 3.8 Baader photographic grade solar filter was used because it transmits 16 times the amount of light that is transmitted by an OD 5.0 visual/photographic solar filter. This will give the best chance for the sensor to detect the CaK light if the UV/IR filter will allow it to pass.

As seen below, in a short opportunity between the clouds, the system worked well and revealed more detail of the photosphere than normal white light filtering. There was no noticeable vignetting. 

As this system works, it should also work with the Altair 2nm G-band Solar Contrast Filter 430.3 nm peak transmission.

Ca K-line image as seen on the Seestar S50 preview screeen

More work needs to be done to determine the best exposure setting when imaging with this setup. Because of clouds, very little time was available to optimise this. However, automatic exposure and gain seems to give a reasonable result.

The RAW AVI data were debayered and stacked in Autostakkert! with 1.5 drizzle (as the Seestar S50 is slightly under-sampled). The stacked image was wavelet processed in waveSharp, and post processed mainly in the Gimp 2.10.

Seestar S50 Ca K-line solar image August 9

The same situation occurred the next day on August 10 but with 252 debayered and stacked RAW AVI frames and post processing, another acceptable Ca K-line image was obtained 

Seestar S50 Ca K-line solar image August 10

The results of this experiment are very encouraging. Whilst the assembly holding the OD 3.8 Baader solar filter and the double stacked Ca K-line filter worked fine, it may be possible to build a more compact assembly.

It is not known if this system would work with Ca K-line filters such as the Antlia 3nm CaK filter or whether it would yield even better results. It remains for others with different bandpass Cak filters to try.

Once again, the Seestar S50 is shown to be a serious and capable 'smart' telescope. 

Feature release of AstroDMx Capture Version: 2.9.1

 Feature release of AstroDMx Capture Version: 2.9.1

Nicola has released a new version of AstroDMx Capture

Mutatis mutandis

Added: Exposure values can now be entered with floating point accuracy. For example, 3.25ms

Added: High full-well control for supported ToupTek derived cameras

Added: Low noise control for supported ToupTek derived cameras. This control is on by default, turning it off can significantly increase the frame-rates

Added: Taillight control for supported ToupTek derived cameras. This control is able to turn off the telltail lights on the back of the camera

Added: Mount sync function for INDI mount control (see release notes for more information)

Added: Native support for Mallincam (ToupTek-Derived. Linux and macOS only)

Added: Native support for Bresser (ToupTek-Derived. Linux and macOS only)

Added: Improved mount nudge functions. The mount can now be nudged, North-East, North-West, South-East and South-West. This is in addition to the usual North, South, East and West nudge functionality

Changes: Complete rewrite of the ToupTek implementation (see the release notes for more information)

Changes: Improvements to the INDI camera implementation (as well as bug fixes)

Changes: Complete rewrite of the INDI configuator (this is to facilitate the upcoming INDIGO implementation)

Changes: The busy indicator UI component no longer gets in the way of other UI components

Removed: Registax optimised AVI (see release notes for more information)

Updated: Altair SDK

Updated: Toupcam SDK

Updated: Omegoncam SDK

Updated: StarshootG SDK

Updated: Risingcam SDK

Updated: OGMA SDK

Updated: Atik SDK

Updated: SVBONY SDK

Updated: PlayerOne SDK

Bug fixes and other improvements

AstroDMx Capture download and further details can be found HERE

The Sun in Ca K-line light.

Two overlapping 3000-frame AVIs were captured with AstroDMx Capture for Windows through an f/5.5 Ekinox 80mm ED refractor fitted with a Baader OD 3.7 solar filter, with an SVBONY SC432M air-cooled CMOS camera, fitted with a Baader Ca K-line filter and a 5x Balow lens alone (giving 3x increase in focal length). 

The equipment used

AstroDMx Capture for Windows was used to capture the two, overlapping 3000 frame AVIs in 8 bit mono.

Flat frames were captured while the scope was pointing at the Sun. using a material that I have previously used for making H-alpha solar flatfields. It is 0.1mm thick, translucent thermoplastic polyurethane, frosted waterproof material. The material was stretched over the front of the Baader solar filter material and was held in place with a rubber band. The material was a low cost purchase from Amazon and proved to be a very effective diffuser.

The setup for flat field capture

The best 95% of the frames in each AVI were stacked in Autostakkert!4 with 1.5 Drizzle. The two resulting images were stitched in Microsoft ICE. The image mosaic was wavelet processed in waveSharp and post processed in GIMP and ACDSee.

Ca K-line image of the Sun

Full size image

Although the SC432M camera is intended for use with long focal length telescopes, this experiment shows that it can be used successfully with short focal length scopes and a Barlow lens. It must also be remembered that the diffuser material is NOT a solar filter and MUST be used in conjunction with the proper solar filter if the Scope is pointing at the Sun. However, it can be used without the solar filter only if the scope is pointing at a different part of the sky, well away from the Sun in order to capture flat fields.