Swansea Astronomical Society Blog

Jupiter with Ganymede and Io in transit:

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During the SAS members viewing and imaging night at the Brian Stokes Cygnus Observatory an SER was taken using Asgtro DMx Capture with an ASI 462C camera fitted to a Meade LX200 Classic telescope. The data were taken just after Ganymede popped into view after being shaded by Jupiter’s shadow and Io and its shadow began their transit across Jupiter. Usually Io's high albedo makes it tricky to see against the similarly coloured surface, but this transit was against the lower equatorial belt making it much easier to pick out against the brownish/ orange hue of the cloud belt. The data were stacked in Autostakkert!4, wavelet processed in Registax and further processed in Pixinsight and Adobe Photoshop 2024 as a greyscale image.

M33:

A 2 hour LRGB/Ha edit of M33 (Triangulum galaxy) imaged with a SkyWatcher Esprit 80ED triplet refractor fitted with a field flattener and a ZWO ASi533MM Pro mono camera and filter wheel. The data were stacked and processed in Pixinsight and Adobe Photoshop 2024.

Chris Bowden

posted by astroimager  # 11:38 PM 0 Comments

ISS Lunar transit in daylight

Video of the ISS recorded transiting the Moon as viewed from south Wales on the morning of 19th December at 09:20 using a Sony ZV-E10 camera fitted with a 350mm zoom lens. In this animation of 101 frames, the ISS can be seen as a small white spec travelling diagonally upwards from the bottom right of the frame. At the time of transit the ISS was some 678 miles away with an angular size of just 25.3 arc seconds, crossing the Moon at an altitude of just 18 degrees from the horizon and taking just under 3 seconds to cross the Moon's disc. The camera was placed on an MSM tracker so as to keep the Moon in the frame long enough to record the video at the predicted time which was calculated from the site ISS Transit Finder. An extract of the video was edited in Grass Valley Edius to apply a stabilisation filter to reduce the effect of camera shake resulting from high winds at the time of the transit. The video was then imported into Adobe Photoshop to make individual frames which were then exported into Adobe LightRoom where the frames were sharpened to give sightly higher contrast and then saved as jpegs which were subsequently aligned and cropped in AstroCrop before being re-imported into Adobe Photoshop to further crop and resize the frames and create a gif animation.

ISS transit video

Following the ISS lunar transit, I was lucky enough to be able to also image the ISS transiting the Sun on the very next orbit of the ISS around the Earth in the opposite part of the sky. Once again the ISS was tiny due to it being some 817 miles away, which made its angular size just 21 arc seconds, resulting in the ISS taking 2.2 seconds to traverse the Sun which was at an altitude of just 13 degrees above the horizon. Dodging a rain shower, I set up my rig comprising an iOptron CEM26 mount with a William Optics ZS71 refractor fitted with a Herschel Wedge used for safe solar imaging with an Apollo-M Mini camera. At the published time of transit I used Astro DMx Capture to take an SER of the Sun in white light which also recorded the ISS transiting the Sun. Using SER Player to enhance the contrast and crop the SER, I was able to export an AVI file to show the transit in real time. I also output a series of 183 frames as individual Tiffs for further editing in Adobe Lightroom and Photoshop to create a false colour gif slowed down to show the transit more clearly. Also attached is a montage of the rig being used at the time of the Solar transit and an image of the camera and tracker being used for the earlier lunar transit at the precise time the ISSS transited the Moon.

The Sun in White Light:

Prior to shooting the ISS transit across the Sun I had a clear sky and was able to capture a 3,300 frame SER in Astro DMx Capture using the ZS71 fitted with Herschel Wedge and Apollo-M Mini camera. The data were stacked in Autostakkert!4, wavelet processed in Registax and further processed using Pixinsight and Adobe 2024.

Chris Bowden

posted by astroimager  # 11:33 PM 0 Comments

A three minute RAW AVI was captured of the 75.2% waning Moon through fast moving, high clouds with a Seestar S50 telescope. The AVI was debayered and stacked with in Autostakkert!4. The Stacked image was wavelet processed in waveSharp and further processed in the Gimp 2.10

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75.2% waning Moon

Steve Wainwright and Nicola Mackin

posted by astroimager  # 5:05 PM 0 Comments

I have recently looked at the mitigation of the effects of Hot Pixels that for one reason or another can end up in an astronomical deep sky image using software such as GREYC's Magic for Image Computing.

I am here using RawTherapee to reduce the effects of Hot pixels. RawTherapee is cross-platform software: It is available for Linux, macOS, and Windows. It is free and Open Source: RawTherapee is released under the GPLv3 license. It works perticularly well with a number of RAW formats, but is also very powerful with a large number of other image formats such as TIFF or PNG.

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A section of an image of the Andromeda Galaxy showing red green and blue Hot pixels

An image file containing hot pixels was loaded into RawTherapee and the Details tab was selected. The following is the set of controls that were used together with their settings. (it must be remembered to experiment with settings for each individual image.

Details tab

    Impulse noise reduction

        Threshold 55

    Noise Reduction

        RGB

            Aggressive

            Gamma 3

    Median Filter

        Weighted

        Median type 7*7

        Median iterations 3

Animation showing before and after applying the above controls to the image

Although it is better to avoid hot pixels if possible. RawTherapee is able to substantially mitigate their effects.

Steve Wainwright

posted by astroimager  # 9:34 PM 0 Comments