Category Archives: Astroimaging

    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 o.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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    Spotlight on Elephant’s Trunk

    Elephant's Trunk Nebula

    The Elephant’s Trunk Nebula (IC 1396A)

    • Telescope: Stellarvue SVA130T-IS
    • Mount: Losmandy G-11 with Gemini 2 controller
    • Autoguiding: 80-mm guide scope with ZWO ASI120-MM Mini guide camera
    • Optical Configuration: 0.72x field flattener & reducer (f/5)
    • Filter(s): S-II (Baader 8.0-nm); H-alpha (Baader 7-nm); O-III (Baader 8.5-nm)
    • Imaging Camera: ZWO ASI1600-MM Cool
    • Camera Gain: 75
    • Sensor Temperature: -10° C
    • Light Frames: 115 S-II subs, 113 H-alpha subs, 124 O-III subs
    • Calibration Frames: 50 darks, 100 biases, 30 flats per filter
    • Total Exposure Time: 1,408 min. [(115 + 113 + 124) x 4 min.] = 23 h 28 min.
    • Pre-Processing: PixInsight, DeepSkyStacker
    • Color Mapping: Red Channel = 100% S-II; Green Channel = 100% H-alpha; Blue Channel = 100% O-III
    • Processing: Photoshop CC
    • Imaging Location: Los Angeles, Calif.

    This image highlights the Elephant’s Trunk Nebula (IC1396A), which is part of a much larger expanse of dust and gas (IC 1396) in the constellation Cepheus. The Nebula lies about 2,400 lightyears from Earth and features a majestic columnar cloud of compressed gases backlit by several newly formed stars, offering a spectacular look into the inner workings of a stellar nursery.

    The image was shot from Los Angeles using narrowband filters in the Hubble Palette (S-II, H-alpha, O-III). It took almost two months to shoot all of the subframes. The final image uses 23 hours and 28 minutes of exposures, which represent about 70% of the total integration time. The result is a very low-noise, high-signal portrait of the Elephant’s Trunk Nebula in all of its glory.

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    The Elephant’s Trunk Nebula

    Elephant's Trunk Nebula

    The Elephant’s Trunk Nebula

    • Telescope: Stellarvue SVA130T-IS
    • Mount: Losmandy G-11 with Gemini 2 controller
    • Autoguiding: Yes
    • Optical Configuration: 0.72x field flattener & reducer (f/5)
    • Filter(s): S-II (Baader 8.0-nm); H-alpha (Baader 7-nm); O-III (Baader 8.5-nm)
    • Camera: ZWO ASI1600-MM Cool
    • Light Frames: 115 S-II subs, 113 H-alpha subs, 124 O-III subs
    • Calibration Frames: 50 darks, 100 biases, 30 flats per filter
    • Total Exposure Time: 1,408 min. [(115 + 113 + 124) x 4 min.] = 23 h 28 min.
    • Gain: 75
    • Sensor Temperature: -10° C
    • Pre-Processing: PixInsight, DeepSkyStacker
    • Color Mapping: Red Channel = 100% S-II; Green Channel = 100% H-alpha; Blue Channel = 100% O-III
    • Processing: Photoshop CC
    • Imaging Location: Los Angeles, Calif.

    The Elephant’s Trunk Nebula (IC 1396A) can be found within a much larger expanse of dust and gas (IC 1396) in the constellation Cepheus. This deep-sky object lies about 2,400 lightyears from Earth and features a majestic columnar cloud of compressed gases backlit by several newly formed stars, offering a spectacular look into the inner workings of a stellar nursery.

    This image of Elephant’s Trunk was shot in the Hubble Palette, made famous by photos from the Hubble Space Telescope. It consists of three sets of 4-min. exposures (subframes) taken through narrowband optical filters designed to pass the light from singly ionized sulfur (S-II), hydrogen (H-alpha), and doubly ionized oxygen (O-III). The total exposure time through all three filters totals 23 hours and 28 minutes. It took almost two months to shoot all of the subframes for this image. The result is a very low-noise, high-signal depiction of the Elephant’s Trunk Nebula in all of its glory.

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