Comets are chunks made of ice, frozen gases and dust (like dirty snowballs). The come from the outer regions of our solar system. When the get close to the Sun they heat up and evaporate. This evaporating gas and dust is blown away by the solar wind and forms the tails of a comet. Therefore the tail always points away from the Sun. Comets are very common but only a few of them get that close to the Earth that they can be seen with naked eye. See also time lapse movies of comet Neowise C/2020 F3.
Fig. 1: The core of the comet Hale-Bopp. Combination of five pictures. — Minolta SRT-101, Vixen Refraktor d=90mm f=1000mm, 1+2+4+8+16s, Fujicolor Super G 400, Raten, 2. April 1997Fig. 2: The wonderful comet Hale-Bopp with a blue gas tail and a grey dust tail. Guided with a telescope. Minolta SRT-101, Minolta MC 300mm f/4.5, Kodak Gold 400, Raten, April 1st, 1997 LS-50Fig. 3: The wonderful comet Hale-Bopp with a blue gas tail and a grey dust tail. Unfortunately some branches of a tree are in the picture. Back then without digital cameras I noticed that only after development of the film. Combination of three pictures. Guided with a telescope. — Minolta SRT-101, Minolta MC 300mm f/4.5, Kodak Gold 400, Raten, 1 April 1997Fig. 4: Comet Hale-Bopp above the woods on the Raten. — Minolta SRT-101, 50mm lens, April 1997Fig. 5: The core of the comet Hale-Bopp. One can see a kind of "shock wave" caused by evaporating gas on a rotating core. Combination of three pictures with eyepiece projection. — Minolta SRT-101, Vixen Refraktor d=90mm f=1000mm, 16+30+60s, Fujicolor Super G 400, Raten, 2. April 1997Fig. 6: It was not as big as Hale-Bopp but it's appearance was very surprising and it came very close to the Earth. One could see it moving through the telescope. — 1996Fig. 7: It was not as big as Hale-Bopp but it's appearance was very surprising and it came very close to the Earth. One could see it moving through the telescope. — 1996Fig. 8: The comet is rising behind the transmission tower on top of Geissberg (Goat Mountain). Composite of 33 single exposures with 22 dark frames with Starry Landscape Stacker 1.8.0. See also my timelapse movie on YouTube. Nikon D3; Δt=6 s; f=70 mm; f/4.0; ISO 3200; 10 July 2020 02:57:35Fig. 9: Shooting the comet C/2020 F3 Neowise at dawn on Bözberg im canton Aargau. In the background the transmission tower on top of Geissberg (Goat Mountain). See also my timelapse movie on YouTube. Nikon D3; Δt=6 s; f=24 mm; f/4.0; ISO 1600; 10 July 2020 03:53:06Fig. 10: The comet C/2020 F3 Neowise at dawn on Bözberg im canton Aargau. In the background the transmission tower on top of Geissberg (Goat Mountain). See also my timelapse movie on YouTube. Nikon D3; Δt=6 s; f=70 mm; f/4.0; ISO 1600; 10 July 2020 04:03:13Fig. 11: HDR composite of the comet C/2020 F3 Neowise. 10 x ISO 800 20s + 10 x ISO 800 10s + 10 x ISO 800 5s + and 3 dark frames each. Post processing with Starry Sky Stacker, Photomatix Pro, Photoshop. Shot on 10 July 2020 on Bözberg in canton Aargau. Nikon D850 with Nikkor 300mm 2.8D, guided on a Vixen GP-DX mount with FS2 controller.Fig. 12: Rise of comet C/2020 F3 Neowise behind the transmission tower on top of Geissberg (Goat Mountain). Composite picture of multiple single frames. See also my timelapse movie on YouTube. 10 July 2020 02:48:41Fig. 13: Composite picture made of ten single frames of the comet C/2020 F3 Neowise. See also my timelapse movie on YouTube. Nikon D850; Δt=20 s; f=300 mm; f/2.8; ISO 800; 10 July 2020 03:17:47Fig. 14: Composite image of comet C/2020 F3 Neowise. 10 exposures at ISO 1600 for 4 seconds with Nikon D850 and Nikkor 300mm 2.8D at f/4. 4 dark frames. 1 flat frame. Guided with Vixen GP-DX mount. Unfortunately the faint ion tail is not visible. It was taken at dusk and later that night there were thin clouds coming. 13 July 2020, Bözberg. Nikon D850; Δt=4 s; f=300 mm; f/4.0; ISO 1600; 12 July 2020 23:13:06Fig. 15: Composite image of comet C/2020 F3 Neowise. Comet: 10 frames at ISO 3200 with 10 seconds exposure time. Nikon D850 with Nikkor 300mm 2.8D at f/2.8, guided with Vixen GP-DX mount. Forest in the foreground without guiding used as mask. 13 July 2020, Bözberg.Fig. 16: Despite some cirrus clouds passing over the sky I could create this composite of comet Neowise. It shows the travel distance of the comet during a time of 20 minutes. Stack and alignment of 50 pictures using Nebulosity from Stark Labs and tracking on comet core. Postprocessing with Photoshop. ISO 800, 20 seconds exposure time, interval 25 seconds. Nikon D850 with Nikkor 300mm 2.8D at f/2.8. 19 July 2020, Bözberg.Fig. 17: Despite some cirrus clouds passing over the sky I could create this composite of comet Neowise. 10 light frames with 20 seconds exposure time at ISO 800 with Nikon D850 and Nikkor 300mm 2.8D plus 50 dark frames. 19 July 2020, Bözberg. Nikon D850; Δt=20 s; f=300 mm; f/2.8; ISO 800; 19 July 2020 01:22:35Fig. 18: I'm not quite sure if the dark stripe left of the ion tail an artefact caused by image processing or actual the comets shadow in its own clowd of dust. The star trails show the comets movement during a time period of 40 minutes. Stack of 67 frames with ISO 800 and 30 seconds exposure time, stacked aligned on comet core with Nebulosity from Stark Labs. Postprocessing with Photoshop. Nikon D850 with Nikkor 300mm 2.8D, Ibergeregg, Switzerland 20 July 2020Fig. 19: Comet C/2020 F3 Neowise - post-processing 20 July 2023 as an exercise with PixInsight and Photoshop. PixInsight: Calibrate bias, dark, flat frames, align approx. 100 images to comet nucleus, integrate, adjust histogram, extract dynamic background. Photoshop: Fine tune highlights, shadows, colours, noise. Nikon D850 with Nikkor 300mm 2.8D at f/2.8, Ibergeregg, Switzerland 20 July 2020.Fig. 20: 16 frames with ISO 800 and 30 seconds exposure time, stacked aligned on stars with Nebulosity. Nikon D850 with Nikkor 300mm 2.8D, Ibergeregg, Switzerland, 20 July 2020
