NGC 1491, Little Pacman

NGC 1491
NGC 1491: Galactic nebula in Perseus; 500 mm Cassegrain 5800 mm f/11.4; SBIG STL11K; 110+30+30+30 min LRGB; Bernese Highlands; © 2011 Radek Chromik

History

This emission nebula that was discovered by Wilhelm Herschel on December 28, 1790 and cataloged as I 258. He noted about it: «Very bright, irregular figure, round, brighter in the middle, 5' long 4' broad. A pretty large star in it towards the following side, but unconnected.» [465] Dreyer cataloged the nebula as NGC 1491 in his «New General Catalogue». [313] Other designation for this H-II region are: LBN 704, Sharpless 2-206, S 206, Sh2-206. [145]

Physical Properties

There are two measured distances on Simbad: 3.0 kpc and 3.3 kpc (9780 and 10'800 light years). The distance to the center of the Milky Way is about 11.1 kpc (36'200 light years). An electron temperature of 8350 K ± 1600 K was measured in the nebula using a radio telescope. [145, 196, 318]

«Revised New General Catalogue and Index Catalogue» Dr. Wolfgang Steinicke, 2021 [277]
DesignationNGC 1491
TypeEN
Right Ascension04h 03m 13.5s
Declination+51° 18' 58"
Diameter25.00 × 25.0 arcmin
Dreyer DescriptionvB, S, iF, bM, r, * inv
IdentificationLBN 704, in Sh2-206

Finder Chart

NGC 1491 is located in the constellation Perseus about one degree north-north-west of the star λ Persei. The constellation is best observed between September and February.

Chart NGC 1491
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

400 mm aperture: With a 21 mm Ethos eyepiece (85x) and without a filter, the nebula stands out more and more clearly from the background with increasing height above the horizon and increasingly darker sky and is easily recognizable with an irregular shape next to a slightly brighter star. With a 16 mm Nagler eyepiece (112x), O-III filter and indirect vision, it is easily recognizable and appears oval shaped with a star. An H-beta does not bring any improvement. With a 9 mm Nagler (200x) and O-III filter, the image is too dark. Without a filter, the nebula is easier to see and, together with the asterisks in the area, forms the nicer sight. A worthwhile object. — Taurus T400 f/4.5 Dobsonian, Hasliberg Reuti, 6. 11. 2021, Bernd Nies

762 mm aperture: With the 13 mm Ethos eyepiece (193x) and O-III filter, the nebula is visible with significantly more structure and direct vision. The star appears just outside the nebula. It looks something like the Pacman Nebula NGC 281. — 30" f/3.3 Slipstream Dobsonian, Hasliberg Reuti, 6. 11. 2021, Bernd Nies

References

145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
196Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
313«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
318«The electron temperatures of HII regions S 201, S 206 and S 209: multi-frequency GMRT observations.» Omar, A.; Chengalur, J. N.; Roshi, D. A.; arXiv:astro-ph/0205061
465«Catalogue of 500 new nebulae, nebulous stars, planetary nebula:, and clusters of stars; with remarks on the construction of the heavens» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1802; DOI:10.1098/rstl.1802.0021