Category Archives: Astroimaging

    Pickering’s Triangle

    Pickering's Triangle

    Pickering’s Triangle shot in HaOiiiRGB

    • Telescope: Askar FRA 500 (90-mm aperture)
    • Mount: ZWO AM5 (strain-wave gear drive)
    • Autoguiding: Off-axis guider with ZWO ASI120-MM Mini camera
    • Controller: ZWO ASIair
    • Optical Configuration: Flat-field quintuplet Petzval refractor (f/5.6 w/o reducer)
    • Filterwheel: RGB (Astronomik 1.25-in.); H-alpha (Baader 7-nm); O-III (Baader 4-nm)
    • Imaging Camera: ZWO ASI1600-MM Pro
    • Camera Gain: 70 (RGB); 0 (H-alpha & O-III)
    • Sensor Temperature: -10° C
    • Light Frames: ~120 (H-alpha & O-III); 40 (RGB)
    • Calibration Frames: 60 darks, 60 biases, 30 flats per filter
    • Total Exposure Time per Filter: 8 h (H-alpha & O-III); 0.66 h (RGB)
    • Pre-Processing & Processing: PixInsight
    • Post-processing: Photoshop CC
    • Imaging Locations: Sierra Nevada Mountains (8,600 ft.); Los Angeles, Calif.

    Pickering’s Triangle is part of the expansive Cygnus Loop formation in the constellation Cygnus. This vast structure of emission nebulae, which now spans some 120 light years of space, is the product of an ancient supernova, the remnants of which are still streaking through the interstellar medium (ISM). The energy released into the ISM causes it to glow at wavelengths across the spectrum from x-rays to radio waves. This image, taken in the visible spectrum, captures the continuum emissions of dust/molecules (white) as well as the line emissions from hydrogen atoms (red) and oxygen atoms (teal).

    The nebula was discovered in 1904 and named for the director of the Harvard College Observatory Edward Pickering, but it was actually found by his assistant Williamina Fleming; consequently, it is also known as Fleming’s Triangle. Fleming discovered and cataloged many other astronomical objects, including the Horsehead Nebula.

    To photograph this object with my new astrograph, RGB subframes were shot first at a dark-sky location far away from the city. Back in the city, I then shot 8 hours of narrowband subframes in H-alpha and 8 hours in O-III. Collection of all image data took about a month and a half to complete. All imaging sessions were fully automated with the ASIair.

    To ensure the highest color fidelity of the star field and nebula, RGB color calibration was achieved during processing using Gaia’s latest photometric data (https://www.aanda.org/articles/aa/full_html/2016/11/aa29272-16/aa29272-16.html#app) and PixInsight’s Spectrophotometric Color Calibration tool. Blending the narrowband data into a final HaOiiiRGB image was accomplished using the PixelMath tool. The latest AI image-processing tools were also employed for noise reduction, star-field optimization, and deconvolution. The resulting image reveals Pickering’s Triangle and its surrounding star field with superlative color and clarity.

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    Moon Craters

    Moon Craters © 2025 T.V. Higgins

    Craters

    • Telescope: Askar FRA 500 (90-mm aperture)
    • Mount: ZWO AM5 (strain-wave gear drive)
    • Autoguiding: N/A
    • Controller: ZWO ASIair
    • Optical Configuration: Flat-field quintuplet Petzval refractor (f/22.4 w/ 4x Barlow)
    • Filter: Infrared (Baader 2-inch, 685-nm IR pass-filter)
    • Imaging Camera: ZWO ASI1600-MM Pro
    • Camera Gain: Zero
    • Sensor Temperature: Ambient
    • Video: 2.5 min. @ 960P, 1,280 x 960 resolution
    • Calibration Frames: N/A
    • Pre-Processing & Processing: AutoStakkert; PixInsight
    • Post-processing: Photoshop CC
    • Imaging Location: Los Angeles, Calif.

    This image of our next-door neighbor was processed from a 2.5-min. video shot in infrared (details above). The “lucky-imaging” video was pre-processed using AutoStakkert to reduce blurring caused by atmospheric turbulence. Further blur reduction was done with RC-Astro’s BlurXTerminator AI tool in Pixinsight, with some additional sharpening in Photoshop. Finally, I cropped the image to a 9:16 aspect ratio ideal for cell-phone wallpaper display.

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    New Ultraportable Astrograph

    Ultraportable Astrograph

    New ultraportable astrograph

    When photographing the cosmos, you often need to pack up and move your imaging gear. Whether you’re chasing an eclipse or an ISS transit or looking to get away from the city for some quality RGB data, sometimes you just have to pick up and go. And that is why I invested in my new ultraportable astrograph pictured above. The entire rig—astrograph, accessories, mount, and tripod—weighs just 33 pounds, and everything you see riding atop the mount fits into a single carry-on.

    This is the rig I used to photograph the Cygnus Loop mosaic featured in a recent post (October 19). It consists of a 90-mm Askar FRA 500 quintuplet apochromatic astrograph fitted with a ZWO EAF, an Askar off-axis guider, a ZWO ASI 120-MM Mini guide camera, a ZWO EFW (5-filter Mini), and a ZWO ASI1600-MM Pro imaging camera. Riding atop this whole assembly is a ZWO ASIair controller, which controls everything, including the ZWO AM5 strain-wave mount below it.

    The AM5 mount uses an innovative strain-wave gearing technology that frankly I had never heard of before, even though it’s been around for as long as I have. The drive has zero backlash! What’s more, my average guiding accuracy with this drive is 0.4 arcseconds (RMS)! Also, its enormous torque avoids the need for a counterweight with payloads up to 13 kg, and it can handle payloads up to 20 kg with a counterweight.

    The Askar FRA 500 utilizes a quintuplet Petzval optical design that employs an apochromatic triplet paired with a field-flattening doublet. The field is the flattest I’ve ever experienced, producing round stars over the entire sensor area of my ASI1600-MM Pro camera, all the way to the corners. The manufacturer (Sharpstar) claims that the flat field of this astrograph can also accommodate full-frame sensors.

    The whole rig sits atop a 5-lb ZWO TC-40 carbon-fiber tripod, which I’ve outfitted with three sturdy rubber foot pads to improve its stability even more. The tripod has a load capacity of 50 kg and collapses to a packable length of 500 mm or just over 19 inches.

    This little workhorse is not just an ultraportable rig, it also has streamlined my imaging sessions with fully automated features that maximize my imaging time. Polar alignments typically take just two or three minutes, and meridian flips go off without a hitch. I can literally set it and forget it for the night. No more babysitting. If only it would put the lens cap back on the scope for me at the end of the night.

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    Eastern Veil Nebula, Take Three

    Eastern Veil Nebula

    Eastern Veil Nebula shot in HaOiiiRGB

    • Telescope: Askar FRA 500 (90-mm aperture)
    • Mount: ZWO AM5 (strain-wave gear drive)
    • Autoguiding: Off-axis guider with ZWO ASI120-MM Mini camera
    • Controller: ZWO ASIair
    • Optical Configuration: Flat-field quintuplet Petzval refractor (f/5.6 w/o reducer)
    • Filterwheel: RGB (Astronomik 1.25-in.); H-alpha (Baader 7-nm); O-III (Baader 4-nm)
    • Imaging Camera: ZWO ASI1600-MM Pro
    • Camera Gain: 70 (RGB); 0 (H-alpha & O-III)
    • Sensor Temperature: -10° C
    • Light Frames: ~120 (H-alpha & O-III); 40 (RGB)
    • Calibration Frames: 60 darks, 60 biases, 30 flats per filter
    • Total Exposure Time per Filter: 8 h (H-alpha & O-III); 0.66 h (RGB)
    • Pre-Processing & Processing: PixInsight
    • Post-processing: Photoshop CC
    • Imaging Locations: Sierra Nevada Mountains (8,600 ft.); Los Angeles, Calif.

    The Eastern Veil Nebula, part of the Cygnus Loop, is a favorite deep-sky object (DSO) among professional and amateur astronomers alike. It is created from the shock wave and remnants of an ancient supernova explosion hurtling through the interstellar medium (ISM) at hypersonic speeds. The energy released into the ISM causes it to glow at wavelengths across the spectrum from x-rays to radio waves. This image, taken in the visible spectrum, captures the continuum emissions of dust (white) as well as the line emissions from hydrogen atoms (red) and oxygen atoms (teal).

    To photograph this object with my new rig, RGB subframes were shot first at a dark-sky location far away from the city. Back in the city, I then shot 8 hours of narrowband subframes in H-alpha and 8 hours in O-III. All imaging sessions were fully automated with the ASIair.

    To ensure the highest color fidelity of the star field and nebula, RGB color calibration was achieved during processing using Gaia’s latest photometric data (https://www.aanda.org/articles/aa/full_html/2016/11/aa29272-16/aa29272-16.html#app) with PixInsight’s Spectrophotometric Color Calibration tool. Blending the narrowband data into a final HaOiiiRGB image was accomplished using the PixelMath tool. The latest AI image-processing tools were also employed for noise reduction, star-field optimization, and deconvolution. The resulting image reveals the Eastern Veil Nebula and its surrounding star field with superlative color and clarity.

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    The Cygnus Loop: A Cosmic Shock Wave

    Mosaic Image of Cygnus Loop

    Six-panel (3 x 2) mosaic of the Cygnus Loop

    • Telescope: Askar FRA 500 (90-mm aperture)
    • Mount: ZWO AM5 (strain-wave gear drive)
    • Autoguiding: Off-axis guider with ZWO ASI120-MM Mini camera
    • Controller: ZWO ASIair
    • Optical Configuration: Flat-field quintuplet Petzval refractor (f/5.6 w/o reducer)
    • Filterwheel: RGB (Astronomik 1.25-in.); H-alpha (Baader 7-nm); O-III (Baader 4-nm)
    • Imaging Camera: ZWO ASI1600-MM Pro
    • Camera Gain: 70 (RGB); 0 (H-alpha & O-III)
    • Sensor Temperature: -10° C
    • Light Frames per Panel: ~120 (H-alpha & O-III); 40 (RGB)
    • Calibration Frames: 60 darks, 60 biases, 30 flats per filter
    • Total Exposure Time per Filter per Panel: 8 h (H-alpha & O-III); 0.66 h (RGB)
    • Pre-Processing & Processing: PixInsight
    • Post-processing: Photoshop CC
    • Imaging Locations: Sierra Nevada Mountains (8,600 ft.); Los Angeles, Calif.

    The Cygnus Loop, a favorite deep-sky object (DSO) among professional and amateur astronomers alike, is created from the shock wave and remnants of an ancient supernova explosion hurtling through the interstellar medium (ISM) at hypersonic speeds. The energy released into the ISM causes it to glow at wavelengths across the spectrum from x-rays to radio waves. This image, taken in the visible spectrum, captures the continuum emissions of dust/molecules (white) as well as the line emissions from hydrogen atoms (red) and oxygen atoms (teal).

    The most recent and reliable distance estimates using Gaia astrometry data (https://academic.oup.com/mnras/article/481/2/1786/5088377) place the Cygnus Loop at about 2,400 light years (735 parsecs) from Earth, where it takes up 3 degrees of our sky (six Moons wide). This means that its actual diameter is about 120 light years.

    To photograph such an extensive DSO with my new rig meant shooting a six-panel mosaic. RGB subframes for each panel of the mosaic were shot first at a dark-sky location far away from the city. Back in the city, I shot 8 hours of narrowband subframes for each panel in H-alpha and O-III. All imaging sessions were fully automated with the ASIair. Shooting all of the ~2,100 subframes for this mosaic took about a month and a half.

    To ensure the highest color fidelity of the star field and nebulae, RGB color calibration was achieved during processing using Gaia’s latest photometric data (DR3) through PixInsight’s Spectrophotometric Color Calibration tool. Blending the narrowband data into a final HaOiiiRGB image was accomplished using the PixelMath tool. The latest AI image-processing tools were also employed for noise reduction, star-field optimization, and deconvolution.

    The full-resolution mosaic image is 10,800 x 10,800 pixels, covers about 16 square degrees of sky, and reveals the entire Cygnus Loop and its surrounding star field with superlative color and clarity.

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