Swansea Astronomical Society Blog

Using a borrowed 70mm Altair Starwave triplet refractor fitted with a 0.8 x FR (courtesy of Anne Startup) I did some more imaging; this time of a galaxy, a star cluster and a nebula. The night was dominated by one of the strongest and sustained displays of aurora which covered most of the sky and at one point was so bright it was easily visible with the naked eye. As beautiful is this display was, the DSO imaged were full of aurora which required considerable effort to remove them. A mobile phone and a Sony A77 milc camera were used to snap the aurora as it changed colour; one of which shows the scope in operation.

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Aurora Borealius

M45: 4 hours of RGB

NGC 6823/ NGC 6820: 1.4 hours of SHO and a further 1.4 hours of RGB. Three versions were produced; an RGB one, and SHO one with RGB stars and a combined blend of the two

RGB

M51: an hour of RGB

The DSO images were all captured in NINA and processed in Pixinsight/Adobe Photoshop 2024.

Chris Bowden

posted by astroimager  # 1:42 PM 0 Comments

The Sun in White light and CaK light with a Seestar S50. The CaK AVI was captured 277 minutes after the white light AVI. 3 min RAW AVIs debayered and stacked in Autostakkert!4 with 1.5 Drizzle, wavelet processed in waveSharp and further processed in the Gimp 2.10 and ACDSee.

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Ca K-line light

Steve Wainwright and Nicola Mackin

posted by astroimager  # 11:34 PM 0 Comments

Click on the image to get a closer view. 64 minutes worth of 10s exposures of IC63 with a Seestar S50; The Ghost of Cassiopeia. Debayered stacked and part processed in PixInsight and further processed in The Gimp 2.10 and ACDSee.

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IC63

Steve Wainwright and Nicola Mackin

posted by astroimager  # 11:29 PM 0 Comments

RAW 60s unguided exposures were captured of NGC6914 through A William Optics 81mm APO refractor with an Altair Quadband filter and an Altair Hypercam 533C OSC 14 bit CMOS camera. Live Stacking was carried out. The stacked image rapidly improves as per the graph of S/N vs number of stacked frames.

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Speeded up animation showing AstroDMx Capture as each of the 1 minute RAW FITS file is downloaded and incorporated into the stack

Steve Wainwright and Nicola Mackin

posted by astroimager  # 7:37 PM 0 Comments

I captured images of the Aurora Borealis, also known as the Northern Lights, on the night of October 10th, 2024, at Rhossili Bay on the Gower Peninsula. I used a 24mm Canon prime lens at f/2.8, with my Canon 1300D DSLR camera mounted on a static tripod. The settings were 8 seconds and ISO 1600.

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Chris Playle

posted by astroimager  # 3:53 PM 0 Comments

These sketches were made at Kelling Heath

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Jim Startup

posted by astroimager  # 5:16 PM 0 Comments

With just over an hour of clear skies available I used an Altair 70mm Starwave triplet refractor fitted with a 0.8 x FR to image M13 and NGC 6823 in RGB and red (converted to greyscale). For M13 15 x 60s subs of each channel were captured and the data integrated and processed in Pixinsight and Adobe Photoshop 2024 to produce the colour image with a 45min total exposure. For NGC 6823 just 5 x 240s subs (20 mins in total) were captured before the clouds stopped play. These were integrated in DSS and processed in Pixinsight/Adobe 2024 converting the red to greyscale.

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M13 is known as the "Great globular cluster" in Hercules and is one of the finest globular clusters visible from the UK comprising ~ 300,00 stars some 25,000 LY from Earth. Also captured in the same image is the small galaxy visible to the bottom right which is NGC 6207 (mag 12)  lying ~ 30 million light-years from Earth.

M13

NGC 6823 is an open star cluster in Vulpecula which lies about 6000 LY away and is surrounded by a reflection nebula with the emission nebula NGC 6820 also close by.

NGC 6823 

Chris Bowden

posted by astroimager  # 3:03 PM 0 Comments

Nicola is working on the implementation of live stacking in AstroDMx Capture. Live stacking is a process favoured by astronomers using EAA (Electronically Assisted Astronomy). The imager can watch the image build on the preview screen and watch the Signal/Noise ratio increase as each new image is captured and added to the stack. Frequently relatively short exposures are used. In our experiments we have combined regular long, guided exposures (typically 5 minute RAW FITS files) with live stacking.

The implementation is not yet complete, but works in all the essentials and enables us to make this demonstration of the process. Thirty four RAW 5 minute exposures were captured of NGC700 through A William Optics 81mm APO refractor with an Altair Quadband filter and an Altair Hypercam 533C OSC 14 bit CMOS camera. The live stacking shown here is with uncalibrated frames, but of course, frame calibration in live stacking will be implemented as will image rejection.

For this experiment we used the camera simulator that Nicola has built into AstroDMx Capture. It is selected from the camera list in the usual way but uses previously captured RAW FITs files. If a real camera is selected, then the live stacking occurs on the captured frames as they are captured. This will be the next experiment. 

The signal to noise ratio increases as the square root of the number of frames stacked

Increase in Signal to Noise as a function of the number of frames stacked

Live stacking results speeded up 200 times.

Steve Wainwright and Nicola Mackin

posted by astroimager  # 7:12 PM 0 Comments

A Player One Apollo-M Mini camera fitted with a x2 Barlow lens was inserted into a Coronado PST mounted on a geared head attached to an AstroTrac running in solar tracking mode which was also mounted on a geared head attached to a mini Pier. Several SER files were then captured using AsgtroDMx Capture as the Sun passed between clouds, with only a portion of each file capturing frames unobstructed by clouds. The best frames from each SER file were then collated with 20% of the frames stacked separately in Autostakkert!4, wavelet processed in Registax and further processed in Pixinsight. The processed images were then blended together in Adobe Photoshop 2024 to produce a false colour image of the whole solar disc image comprising some 2,341 frames showing both surface detail and solar prominences. A further SER file of some 2,000 frames was then stacked in Autostakkert!4 using 15% of the frames, wavelet processed in Registax and the mono Tiff file then finished off in Adobe Photoshop 2024, where sections of interest were divided into three separate mono images.

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The Sun in H-alpha light

posted by astroimager  # 6:53 PM 0 Comments

I imaged the Pelican Nebula at the Kelling Heath Equinox Starparty earlier this month using my ASI533MC, Altairastro X-Wave 80mm refractor and CEM40 mount. It was captured over 4 nights, 36 x 5 min Ha/Oiii and 63 x 5 min Sii/Oiii subs, though I did lose some due to cloud. Total 8 and 1/2 hours.

All processing was done using Pixinsight. The subs were integrated using WBPP and the individual Ha/Oiii and Sii/Oiii masters had gradientcorrection applied before using a script, DBXtract which creates separate Ha,Oiii and Sii mono images together with a SHO combination.

I then used SPCC to colour calibrate the stars in nb mode followed by BlurX to tidy up the stars and bring out some detail in the nebula.

Generalised hyperbolic stretch was used to create a non-linear image before I removed the stars using StarX. An application of Deconvolution and NoiseX reduced the noise in the image whilst maintaining details. Narrowbandnormalisation then adjusted the Ha and boosted Oiii and Sii to improve the colours in the image. HDRtransformation increased the detail in the Pelican followed by some histogram and curves adjustments.

I then used Pixelmath to unscreen the star image into the nebula image and did a few final curves adjustments.

My second image is an HOO version. I basically followed the method above but used Easy soft stretch to create the non-linear image instead of Generalised Hyperbolic stretch.

This is my best attempt at the Pelican Nebula to date.

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Pelican nebula SHO

Anne Startup 

posted by astroimager  # 2:36 PM 0 Comments

The equipment comprised a William Optics 81 mm ED APO refractor with a 0.8 flattener/reducer ED APO refractor with an Altair magnetic 2" filter holder with an Altair Quadband filter, a ZWO EAF and an Altair Hypercam 533C 14 bit OSC CMOS camera.  

RAW data were captured with AstroDMx Capture for Windows. The scope was mounted on an AVX GOTO mount which was controlled by AstroDMx Capture via an INDI server running on the imaging computer indoors.

The mount was placed on permanent marks on the ground which quickly gives quite a good polar alignment if care is taken with the placement of the tripod feet.

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.

The data were debayered, stacked, SPCC processed and star Xterminated in PixInsight, further processing was done in GraXpert, Cosmic Clarity at the command line, The Gimp 2.10 and PhotoPea.

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NGC7000 RGB stretched with linked channels

NGC700 linked and unlinked channels blend

Steve Wainwright and Nicola Mackin

posted by astroimager  # 4:32 PM 0 Comments

This is the Iris Nebula (NGC 7023) taken over 2 nights at the end of September / beginning of October in LRGB.

Telescope: Celestron C8

Mount: EQ6r Pro

Camera: ASI1600mm pro

Acquisition: KStars

Processing: PixInsight (incl Graxpert, RC tools) 

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John Evans

posted by astroimager  # 3:08 PM 0 Comments

Many galaxies contain many nebula and bringing these out in an RGB Image can be difficult. One way to do this is to combine a Narrowband Channel image with one channel of the colour image.

One of the easiest to do is combining Ha with the red channel. A complication with the normal methods of achieving this is that the red channel can become overwhelming when the Ha is added to it.

One method to prevent this problem is continuum subtraction where the signal from the Ha channel has the Broadband Red channel subtracted to leave only the most prominent areas of Ha. 

These are the areas that astro-imagers want to bring out. Prior to the launch of a Pixinsight Script by Seti Astro, continuum subtraction required a set of complex formulae in Pixinsight Pixel Math or complex but clever trickery in Photoshop. 

Below is an image of Bodes Nebula (M81 & M82) that has been developed using LRGB+Ha and continuum subtraction. The Ha signal in this image ha been exaggerated to show the effect. 

However, i think it adds a lot to the interest of these galaxies.

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M81 and M82

Paul Howat

posted by astroimager  # 3:04 PM 0 Comments

Do you sometimes feel constrained by combining narrowband images in the same combinations? I have and so when the Narrowband Colour Mapping Script and Image Blend were released in Pixinsight last year a fairly simple method for colouring Narrowband Channels became available. This added the power of Photoshop Layers and Blending styles to Pixinsight. The way these tools are used depends on the relative signal strengths of each channel in a DSO. Experimentation is great fun away from the constraints of the usual HSO, HSO. HOO blending palettes.

Here is an example that i think show the power of this scripts/processes to display Deep Sky Objects in a different way.

I collected 18 hours of integration time on the Cone and Christmas Tree Cluster. Six hours each of Ha; OIII and SII. Having process the image in the Hubble Palette, i felt there must be a more dramatic way of  showing the dramatic gas clouds surrounding Nebula. This is the result having spent a few hours trying different colours and blends of the channels. 

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Paul Howat

posted by astroimager  # 2:59 PM 0 Comments

There are a number of ways of blending Narrowband channels in astrophotography. The three channels are Ha (Hydrogen Alpha); OIII (Oxygen) and SII (Sulpher)

These are classically combined in the Hubble Palette with SII mapped to RED; Ha mapped to GREEN and OIII mapped to BLUE. This can be seen in the Rosette Nebula photo below. This palette allows for the three separate channels to contribute to the structure of the image instead of OIII and SII being overwhelmed by the much stronger Ha signal.  

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There are a couple of new Scripts in Pixinsight that allow the colouring, balancing and blending of each of the channels to any colour combination. This can be achieved in Photoshop quite easily but required complex formula’s in Pixinsight. 

The balancing of two or three channels is carried out in Narrowband Normalisation. Colouring is carried out in Narrowband Colour Mapper and blending in Image Blend. These three processes/scripts allow for more creativity and experimentation 

when combining the separate monochrome channels to a colour image. One recent use of these scripts was described by Adam Block a renowned astro photographer.

In simple terms two images are created from the three mono NB channels and then blended together. 

An HOO image is created and calibrated in Narrowband Normalisation.

Then the SII channel is coloured to yellow/orange in Narrowband Colour Mapper script.

These two images are then blended together in Image Blend to produce the image above. 

This image is more dramatic than the Hubble Palette. Neither are a true representation of the actual nebula colour that we see as this is completely red. However they both represent the structure of the nebula and the contribution of each of the

gasses that comprise the majority of the nebula. This is just one of the ways to use these scripts.

Paul Howat

posted by astroimager  # 2:54 PM 0 Comments