Esperimenti nella Laguna
While surfing the web a long time ago I came across an image of this very subject, which struck me a lot. The author, Fred Vanderhaven, who received a well-deserved APOD for this job on June 15, 2008, had made a great version of this nebula using a 12 “instrument.” So I decided to try a long-focussed shooting to see that with my own Modest means (Celestron 11 HD) could get a similar result. Unfortunately, it was about getting a subject always low on the horizon, and more so in the most polluted area of my bad sky, so the shooting took a long time. Here are some short steps that led me to what I consider to be one of my best pictures.
It was necessary to select the sessions obtained with good seeing to obtain a total of almost 11 hours in the halpha channel at both f6 and f10: a good starting point.
The amount of signal turned out to be sufficient to experience particularly aggressive deconvolution algorithms such as those of Van Citter or Wiener.
Using 312 minutes in the sulfur spectrum bandwidth and 1.74 hours in oxygen (over 36 minutes in blue and 30 in red in order to give a more natural touch to the star component) I tried to make two color versions. In the former there is no data on sulfur. Fascinating details of the hourglass nebula, bright lagoon heart)
Mixing the sulfur the color tint changes sharply
The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region.
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. In the foreground is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years from the Earth. In the sky of Earth, it spans 90′ by 40′, which translates to an actual dimension of 110 by 50 light years. Like many nebulas, it appears pink in time-exposure color photos but is gray to the eye peering through binoculars or a telescope, human vision having poor color sensitivity at low light levels. The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the Hourglass Nebula (so named by John Herschel), which should not be confused with the better known Hourglass Nebula in the constellation of Musca. In 2006 the first four Herbig–Haro objects were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it. credit: Wikipedia.
|Optics:||Celestron C11 HD @ f 6/ f10|
|Mount:||Avalon M1 / M3 Fast Reverse|
|Camera:||SX H694 / ASI 178|
|Dates/Times:||2015 / 2016|
|Location:||Viterbo, W.Herschel Obs. Italy|
|Exposure:||162 min sess 26.06.2016,
174 min sess 10.07.2016
25 min ASI 178 2 ago 2016 +15 min asi178 2 ago 2016 binn
26.07.2016 asi 178 23,65 min
39 min 28.07.2016 asi 178
tot : 336min periferia , 102min nucleo (asi 178) tot 2016: 438 min
2015 (4/5/6/7 july : selected 219min)
tot lum halpha: 10.95
Lum (halpha): 12,2 h. OIII : 1,74 h ; SII: 312 min;
|Cooling:||avg – 5°|
|Acquisition:||SEquence Generator Pro, Astroart, PHD2|
|Processing:||Iris, Astroart, PI, PS CC.|