View allAll Photos Tagged Subframing
2020.04.18 Removing and patching up the subframe. Fixing a few rusty spots, and repaired the broken diff mount. Waiting now for subframe bushings and reassembly
24 Oct 2024, abt 21:30 EDT, Spotsylvania, Virginia. Canon 85mm f/1.8 lens, Mallincam DS10C camera, ZWO AM5 mount. Exposure, 300 sec, 9 subframes (best of 25), processed in Pixinsight and Photoshop.
Comet was imaged from dusk until it set in the trees. Rejected frames had aircraft/satellite trails or clouds. Images were stacked manually in PS.
from Wikipedia
C/2023 A3 (Tsuchinshan–ATLAS) (or Comet Tsuchinshan–ATLAS or simply Comet A3) is a comet from the Oort cloud discovered by the Purple Mountain Observatory in China on 9 January 2023 and independently found by ATLAS South Africa on 22 February 2023. The comet passed perihelion at a distance of 0.39 AU (58 million km; 36 million mi) on 27 September 2024, when it became visible to the naked eye. Tsuchinshan-Atlas peaked its brightest magnitude shortly after passing the Sun at 9 October, with a magnitude of −4.9 per reported observations at the Comet Observation Database (COBS).
The systematic search performed by the Asteroid Terrestrial-impact Last Alert System detected an asteroidal object with an estimated magnitude of 18.1 in images taken on 22 February 2023 using the 0.5 m f/2 Schmidt reflector at the Sutherland Observatory in South Africa, when the comet was about 7.3 AU (1.09 billion km; 680 million mi) from the Sun. After the first orbit calculations, it was noticed that it was the same as an 18.7 magnitude object reported to the Minor Planet Center by the Purple Mountain Observatory (Zijinshan in Pinyin, Tsuchinshan in Wade–Giles, the latter form being traditional for discoveries from this observatory) which was detected in images taken on 9 January 2023. It had been entered in the objects awaiting confirmation list, but had been removed on 30 January 2023 after no follow up observations were reported and the uncertainty on its predicted position grew to the point that it was considered lost. Based on the naming conventions for comets, it received the name of both observatories.
The object was subsequently detected in older images taken by the Zwicky Transient Facility (ZTF) in Palomar Observatory on 22 December 2022, when it had a magnitude of 19.2–19.6. These deeper and better resolved images also revealed it had a very condensed coma and a small straight tail 10 arcseconds in length, indicating it was a comet. More evidence of cometary activity was later reported by Hidetaka Sato, M. Mattiazzo and Cristóvão Jacques.
By January 2024, the comet had brightened to an apparent magnitude of 13.6 and according to Bob King, author in Sky & Telescope magazine, was visible through 15-inch telescopes at ×142 magnification. The comet was then moving through the constellations of Libra and Virgo. By the end of April it had brightened to about magnitude 10 and could be observed through small telescopes, showing a short tail. The spectrum of the comet on 31 May 2024, when the comet was 2.33 AU from the Sun, indicated strong cyanide emission and that the comet is carbon depleted. The comet had a large dust-to-gas ratio.
In May and June the brightening rate of the comet slowed, with the comet staying between magnitudes 10 and 11, while a dusty tail measuring 5 to 15 arcminutes long was observed visually to extend eastwards. Astronomer Zdenek Sekanina suggested that this indicates that the comet nucleus has been fragmenting, with the fragmentation starting in late March, as indicated by an increase in the brightening rate and the subsequent decrease in dust production, the narrow teardrop-shaped dust tail, and non-gravitional changes in the orbit. He predicted that the comet would disintegrate before perihelion. Observations of the comet with TRAPPIST robotic telescope indicate that dust production reached a minimum in May, when the comet was near a phase angle of zero, and started to increase again one month later, while gas production rates increased slowly throughout that period. In mid June the comet entered the constellation of Leo, in the evening sky. In early July, a faint ion tail measuring about one and half degree in length was observed photographically. After mid July the comet was lost in the Sun's glare until September. In August the comet was observed by STEREO spacecraft to brighten steadily to an apparent magnitude of 7.
The comet was recovered by Terry Lovejoy in the morning twilight on 11 September 2024, when it was located in the constellation of Sextans, at a magnitude of 5.5. The comet was spotted with the naked eye and photographed by astronaut Matthew Dominick on board the ISS on 20 September, followed by fellow astronaut Donald Pettit two days later. The first naked eye observation of the comet from Earth was reported on 23 September, with the comet having an estimated magnitude of 3.3, while its tail was reported to be 2.5 degrees long when it was observed with binoculars.
During the last week of September it was located in the dawn sky, better visible from the Southern Hemisphere, and it was predicted to have brightened to second magnitude. Perihelion took place on 27 September. By 1 October the comet had brightened to magnitude 2 and its tail was estimated to be 10–12 degrees long. After that it moved again in conjunction with the Sun. On 7 October the comet entered the field of view of the SOHO Coronagraph, and continued to be visible until 11 October. Petr Horálek managed to photograph the comet in broad daylight on 8 October. On 9 October 2024, the comet was 3.5 degrees from the Sun. The comet was seen to brighten to a magnitude of −4.9 on that day, becoming one of the brightest comets of the past century. It was the second brightest comet viewed by SOHO since its launch in 1995, after comet McNaught in 2007.
The comet was recovered in the evening sky on 10 October and the next days became visible with the naked eye. It made its closest approach to Earth on 12 October at a distance of 71 million km (44 million mi). The comet after that became dimmer, as it moves away from both the Earth and the Sun, however as the elongation becomes higher, it becomes easier to spot. Earth crossed the orbital plane of the comet on 14 October and as a result an antitail was observed.
When first discovered, the comet was predicted to reach a total magnitude of +3 during perihelion, assuming an absolute magnitude (H) of 7 and 2.5n = 8, when it would have a small solar elongation. Better visibility was predicted about three weeks after perihelion, in mid-October, when it would be around fourth magnitude. Gideon van Buitenen estimated that the comet would reach a magnitude of 0.9 during perihelion and −0.2 at the time of closest approach to Earth, assuming H = 5.2 and 2.5n = 10, and would benefit from the effects of forward scattering.
Revised data from June 2024 suggested that the comet would brighten to an apparent magnitude of 2.2, assuming H = 6 and 2.5n = 7.5, which is the average brightening rate of long-period comets in the inner Solar System. However, the comet is expected to be at least one magnitude brighter due to the effects of forward scattering, which could boost the brightness by several magnitudes around the peak of the effect on 9.8 October 2024. More calculations from early September indicate that accounting for forward scattering, the comet will be brighter than magnitude 0 between 5 and 13 October and peaked at over −4 on 9 October, when it brightened by almost 6 magnitudes due to forward scattering.
The comet has a retrograde orbit, lying at an inclination of 139°. Τhe comet had its perihelion on 27 September 2024, at a distance of 0.391 AU. Τhe closest approach to Earth was on 12 October 2024, at a distance of 0.47 AU. The comet does not approach close to the giant planets of the Solar System. The orbit is weakly bound to the Sun before entering the planetary region of the Solar System. Due to planetary perturbations, the outbound orbit will have a smaller eccentricity than the inbound orbit. So the orbital period and aphelion distance become much shorter. The weakly hyperbolic trajectory may or may not result in the comet being ejected from the Solar System. It is expected to be 200 AU from the Sun in the year 2239.
19 Nov 2025, 23:13 UT; Spotsylvania, Virginia USA. Bortle 4.5 zone.
WO Redcat51 telescope, ZWO AM5 mount and ASI2600MC camera, autoguiding, no calibration frames, no filter, exp 180s, gain 100, bin 1x1, sensor -10°C, autofocus, 27 subframes, drizzled 2x. Data acquired in ASIAir. Processed in PixInsight. Image scale: 3.1 arcsec/pixel.
Clouds: clear
Transparency (AL): 5
Seeing (AL): F
Moon: illuminated 2.5%, age 13 days
Apparent magnitude 4
Apparent size 2°
Appearance:
From Wikipedia
The North America Nebula (NGC 7000 or Caldwell 20) is an emission nebula in the constellation Cygnus, close to Deneb (the tail of the swan and its brightest star) in the night sky. It is named because its shape resembles North America.
On October 24, 1786, William Herschel observing from Slough, England, noted a “faint milky nebulosity scattered over this space, in some places pretty bright.” The most prominent region was catalogued by his son John Herschel on August 21, 1829. It was listed in the New General Catalogue as NGC 7000, where it is described as a "faint, most extremely large, diffuse nebulosity.”
In 1890, the pioneering German astrophotographer Max Wolf noticed this nebula's characteristic shape on a long-exposure photograph, and dubbed it the North America Nebula.
In his study of nebulae on the Palomar Sky Survey plates in 1959, American astronomer Stewart Sharpless realised that the North America Nebula is part of the same interstellar cloud of ionized hydrogen (H II region) as the Pelican Nebula, separated by a dark band of dust, and listed the two nebulae together in his second list of 313 bright nebulae as Sh2-117. American astronomer Beverly T. Lynds catalogued the obscuring dust cloud as L935 in her 1962 compilation of dark nebulae. Dutch radio astronomer Gart Westerhout detected the HII region Sh2-117 as a strong radio emitter, 3° across, and it appears as W80 in his 1958 catalogue of radio sources in the band of the Milky Way.
The North America Nebula covers a region more than ten times the area of the full moon, but its surface brightness is low, so normally it cannot be seen with the unaided eye. Binoculars and telescopes with large fields of view (approximately 3°) will show it as a foggy patch of light under sufficiently dark skies. However, using a UHC filter, which filters out some unwanted wavelengths of light, it can be seen without magnification under dark skies. Its shape and reddish color (from the hydrogen Hα emission line) show up only in photographs of the area.
The portion of the nebula resembling Mexico and Central America is known as the Cygnus Wall. This region exhibits the most concentrated star formation.
At optical wavelengths, the North America Nebula and the Pelican Nebula (IC 5070) appear distinct as they are separated by the silhouette of the dark band of interstellar dust L935. The dark cloud is however transparent to radio waves and infrared radiation, and these wavelengths reveal the central regions of Sh2-117 that are not visible to an ordinary telescope, including many highly luminous stars.
The distances to the North America and Pelican nebulae were controversial, because there are few precise methods for determining how far away an HII region lies. Until 2020, most astronomers accepted a value of 2,000 light years, though estimates ranged from 1,500 to 3,000 light years. But in 2020, the Gaia astrometry spacecraft measured the distances to 395 stars lying within the HII region, giving the North America and Pelican nebulae a distance of 2,590 light years (795±25 parsecs). The entire HII region Sh2-117 is estimated to be 140 light years across, and the North America nebula stretches 90 light years north to south.
HII regions shine because their hydrogen gas is ionised by the ultraviolet radiation from a hot star. In 1922, Edwin Hubble proposed that Deneb may be responsible for lighting up the North America Nebula, but it soon became apparent that it is not hot enough: Deneb has a surface temperature of 8,500 K, while the nebula's spectrum shows it is being heated by a star hotter than 30,000 K. In addition, Deneb is well away from the middle of the complete North America/Pelican Nebula complex (Sh2-117), and by 1958 George Herbig realised that the ionizing star had to lie behind the central dark cloud L935. In 2004, European astronomers Fernando Comerón and Anna Pasquali searched for the ionizing star behind L935 at infrared wavelengths, using data from the 2MASS survey, and then made detailed observations of likely suspects with the 2.2 m telescope at the Calar Alto Observatory in Spain. One star, catalogued J205551.3+435225, fulfilled all the criteria. Lying right in the centre of Sh2-117, with a temperature of over 40,000 K, it is almost certainly the ionising star for the North America and Pelican nebulae.
Later observations have revealed J205551.3+435225 is a spectral type O3.5 star, with another hot star (type O8) in orbit. J205551.3+435225 lies just off the “Florida coast” of the North America Nebula, so it has been more conveniently nicknamed the Bajamar Star ("Islas de Bajamar," meaning "low-tide islands" in Spanish, was the original name of the Bahamas because many of them are only easily seen from a ship during low tide).
Although the light from the Bajamar Star is dimmed by 9.6 magnitudes (almost 10,000 times) by the dark cloud L935, it is faintly visible at optical wavelengths, at magnitude 13.2. If we saw this star undimmed, it would shine at magnitude 3.6, almost as bright as Albireo, the star marking the swan's head.
Here's the 'stonechip' drying in the sun. Was going to remove the suspension components, but it managed to go on so well, I sprayed everything with it!
21x300 second subframes, iso800.
Total exposure 1 hour 47 minutes.
Imaging:
William Optics ZenithStar II 80 ED,
Nikon D5000 with Astronomik CLS filter.
Guiding:
Skywatcher Star Travel 120,
Orion SSAG.
All on
Skywatcher HEQ5 Pro
24th March 2017
Cambridge, UK