{"id":5674,"date":"2016-04-14T17:20:52","date_gmt":"2016-04-14T16:20:52","guid":{"rendered":"http:\/\/outters.fr\/?p=5674"},"modified":"2025-07-15T17:04:14","modified_gmt":"2025-07-15T16:04:14","slug":"leo1-lrgb","status":"publish","type":"post","link":"https:\/\/www.outters.fr\/?p=5674","title":{"rendered":"Leo1 LRGB"},"content":{"rendered":"

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Leo1 LRGB<\/strong>
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\"Leo1<\/a><\/span><\/div><\/div><\/div>
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Image LRGB<\/h2><\/a><\/div><\/div><\/div>
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Commentaires sur l’objet photographi\u00e9<\/span><\/p><\/h1><\/span>

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\"outters-nicolas\"Leo1 reste un d\u00e9fi pour imager une galaxie aussi t\u00e9nue \u00e0 une distance si courte de l’\u00e9toile R\u00e9gulus.<\/p>\n

Les poses RGB ont \u00e9t\u00e9 difficiles \u00e0 r\u00e9aliser car j’avais une \u00e9toile double comme \u00e9toile de guidage, de temps en temps la monture jouait au yoyo sans savoir quelle \u00e9toile choisir.<\/p>\n<\/div>

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Donn\u00e9es techniques
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Donn\u00e9es techniques de prise de vue<\/h2><\/div>
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Object : Leo1 et Regulus<\/span>
\nCommon name :
\nDate : images du 02 decembre 2016 au 26 f\u00e9vrier 2017
\nOptics : Newton SV400 F3,8
\nMount : Paramount ME Num\u00e9ro 1
\nLocation : Orange observatory
\nSeeing FWHM : 2.69 \u00e0 3.47
\nCcd : Moravian G4
\nfilter wheel : Moravian
\nfilters : Astrodon
\nLRVB
\nFocuser :Atlas
\nGuiding : Atik 314L+
\nTemp. out : T\u00b0 de +2.5 \u00e0 +10
\nTemp ccd : -25\u00b0
\nTotal exposure :8.60h
\ntout en binning 1×1
\nLuminance 37 x 10 mn
\nRVB 5 x 10′ x 3<\/div><\/div><\/div>
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Donn\u00e9es scientifiques<\/h2><\/div>
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Leo I<\/b> is a dwarf spheroidal galaxy<\/a> in the constellation<\/a> Leo<\/a>. At about 820,000 light-years<\/a> distant, it is a member of the Local Group<\/a> of galaxies and is thought to be one of the most distant satellites of the Milky Way<\/a> galaxy. It was discovered in 1950 by Albert George Wilson<\/a> on photographic plates<\/a> of the National Geographic Society \u2013 Palomar Observatory Sky Survey<\/a>, which were taken with the 48-inch Schmidt camera<\/a> at Palomar Observatory<\/a>The proximity of Regulus<\/a> and the low surface brightness make it a real challenge to observe it. Medium-sized amateur telescopes (15\u00a0cm or more) and a dark sky appear to be required for a sighting. But some reports of April 2013 tell that one observer with an 11\u00a0cm mini Dobson and even a refractor as small as 7\u00a0cm f\/10 has sighted Leo I under very dark sky conditions.[6<\/a><\/sup><\/p>\n

The measurement of radial velocities<\/a> of some bright red giants<\/a> in Leo I have made possible to measure its mass. It was found to be at least (2.0 \u00b1 1.0) \u00d7 107<\/sup> M<\/i>\u2609<\/sub><\/a>. The results are not conclusive, and do not exclude or confirm the existence of a large dark matter<\/a> halo around the galaxy. However, it seems to be certain that the galaxy does not rotate.[5]<\/a><\/sup><\/p>\n

It has been suggested that Leo I is a tidal debris stream in the outer halo<\/a> of the Milky Way. This hypothesis has not been confirmed, however.<\/p>\n

Typical to a dwarf galaxy, the metallicity<\/a> of Leo I is very low, only one percent that of the Sun<\/a>. Gallart et al. (1999) deduce from Hubble Space Telescope<\/a> observations that the galaxy experienced a major increase (accounting for 70% to 80% of its population) in its star formation rate between 6 Ga<\/a> and 2 Ga (billion years ago). There is no significant evidence of any stars that are more than 10 Ga old. About 1 Ga ago, star formation in Leo I appears to have dropped suddenly to an almost negligible rate. Some low-level activity may have continued until 200-500 Ma. Therefore, it may be the youngest dwarf spheroidal satellite galaxy of the Milky Way. In addition, the galaxy may be embedded in a cloud of ionized gas with a mass similar to that of the whole galaxy.<\/sup>Leo I is located only 12 arc minutes<\/a> from Regulus<\/a>, the brightest star in the constellation. For that reason, the galaxy is sometimes called the Regulus Dwarf<\/i>. Scattered light from the star makes studying the galaxy more difficult, and it was not until the 1990s that it was detected visually.<\/p>\n