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RA: 07h 41m 51.43s
Dec: −14° 43′ 54.9″
Ch: MSA:295, U2:274, SA:12
Type: planetary nebula
Mag: B=?, V=?
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Synonyms: H IV-039
Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "pB, R, resolvable, within the 46th of [Messier], almost of an equal light throughout, 2' diameter, no connection with the cluster, which is free from nebulosity." In the Philosophical Transactions, 1791, Herschel wrote: "When I examined the cluster of stars, following the head of the great dog, I found on the 19th of March, 1786, that there was within this cluster a round, resolvable nebula, of about two minutes in diameter, and nearly of an equal degree of light throughout. Here, considering that the lcuster was free from nebulosity in other parts, and that many such clusters, as well as many such nebulae, exist in divers parts of the heavens, it appeared to me very probable, that the nebula was unconnected with the cluster."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "a very fine planetary nebula, oval, uniform in light, and of a very flat appearance; rather faint; diam in RA = 4 seconds; has a star 15th mag on it, and one 13th mag close to its border. This object is excentrically situated in a superb cluster of stars 12..16th mag. (46 Messier)" On a second occassion he called it "a fine, nearly uniform, slight elliptic planetary nebula, 40 arcseconds diameter. A star 14th mag is excentrically situated in or on it, which is doubtless only superposed and belongs to the fine cluster Mess 46 in which (somewhat north of the most compressed part) this object is situated. A very uncommon and indeed unique combination, if No. 3154 [NGC 2818] be not a case in point."
Lassell, W. (1854) Observations of the nebula of Orion, made at Valletta, with the twenty-foot equatorial. Memoirs R.A.S., 23, 53-62.
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as ". . . a feeble neb. on the northern verge [of NGC 2437], is in Lassell's 20-foot reflector 'an astonishing and interesting object.'; he and the E. of Rosse see it annular; also Buffham with a 9-inch reflector."
Burnham, S. W. () "Measures of planetary nebulae with the 36-inch equatorial of the Lick Observatory", Pub. Lick Obs., vol 2, p159-167. Has a central star and a faint star in the s.p. side of the ring. ... The outside diameter of the nebula is 63.9''.
B, 1'x1', R, planetary with F central star. The f. edge of the ring is more dense than the p. edge, and besides the central star it contains at least three other stars, whcih probably belong to the loose cluster, in the n.f. corner of which this nebula is situated.
Photo Index by Jim Lucyk: Deep Sky Monthly 3/80 p9, Messier Album p106.
The RNGC (Sulentic and Tifft 1973) notes that this is a 11.5 mag planetary nebula.
Listed by the Herschel Club, described as "fairly bright and obvious, circular. 8-inch, 48x."
Harrington calls it "a tiny planetary nebula on the northern outskirts of M46. It shines at 10th mag, appearing like a tiny, gray disk floating among the stars."
William P. Clarke (San Diego, California, USA) writes in The Webb Society Nebulae and Clusters Section Report No. 11, January 1993: "This object, within the open cluster NGC 2437, is a ring about 1' in diameter. The ratio of the ring thickness to its outer radius is about 0.3. One star is inside the ring on the western edge, and another outside the ring on the eastern edge. Central star not visible. OIII filter used. (21-inch f/20, x350)"
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 2438 (PK 231+04.2; PN G231.8+04.1; ARO 46; Sa 2-13) Category: planetary nebula Constellation: PUP Object data: Vmag=10.8; Bmag=10.1; 68"x68" [internal=90", external=137" in IDB]; type IV+II; central star of Vmag=17.5; discovered by Herschel in 1827; ELCAT: [OIII, 496+501nm] = 12 x [Hbeta, 486nm]. RA/DE: 07h41.83m, -14°44.1' (2000.0) Date and UT of observation: 03 January 1995, 23h30UT Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36) Site classification: rural, alt.1650m (5500ft) Limiting magnitude (visual in UMi): 6.31 Transparency (1 to 5 - best to worst): 1 Seeing (1 to 5 - best to worst): 3 Moon up (phase?): no Instrument: Coulter 445mm/17.5" F/4.5 Magnification: 312x Filters used: OIII, UHC
Description: at 312x, medium sized PN, of medium brightness, round with quite sharp edges; estimated to be 70" in diam., obviously annular (ring thickness of 25"); a 45° section of the ring centered on the NW is less contrasty than the rest; a central star of mag14 is somewhat eccentric, halfway between the geometric center and the inner WNW edge of the ring; UHC provides a good contrast gain and OIII a very good one; a mag12 star is 10" from the SE border; this PN is located 6' to the N of M46's central area.
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 2438 (PK 231+04.2; PN G231.8+04.1; ARO 46; Sa 2-13) Category: planetary nebula Constellation: PUP Object data: Vmag=10.8; Bmag=10.1; 68"x68" [internal=90", external=137" in IDB]; type IV+II; central star of Vmag=17.5; discovered by Herschel in 1827; ELCAT: [OIII, 496+501nm] = 12 x [Hbeta, 486nm]. RA/DE: 07h41.83m, -14°44.1' (2000.0) Date and UT of observation: 29 December 1988, ... Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36) Site classification: rural, alt.1650m (5500ft) Limiting magnitude (visual in UMi): 6.0 Transparency (1 to 5 - best to worst): 1 Seeing (1 to 5 - best to worst): ? Moon up (phase?): no Instrument: Japanese Newtonian 4.25" (114mm), F/7.8 Magnification: 72-150x Filters used: -
Description: located at 72x in the stellar background of the M46 open cluster; round and diffuse patch on the cluster's edge; at 100x, surrounded by faint stars; at 150x, homogeneous.
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 2438 (PK 231+04.2; PN G231.8+04.1; ARO 46; Sa 2-13) Category: planetary nebula Constellation: PUP Object data: Vmag=10.8; Bmag=10.1; 68"x68" [internal=90", external=137" in IDB]; type IV+II; central star of Vmag=17.5; discovered by Herschel in 1827; ELCAT: [OIII, 496+501nm] = 12 x [Hbeta, 486nm]. RA/DE: 07h41.83m, -14°44.1' (2000.0) Date and UT of observation: 29 December 1988, ... Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36) Site classification: rural, alt.1650m (5500ft) Limiting magnitude (visual in UMi): 6.0 Transparency (1 to 5 - best to worst): 1 Seeing (1 to 5 - best to worst): ? Moon up (phase?): no Instrument: Meade SCT 8" (203mm), F/10 Magnification: 87-145x Filters used: OIII
Description: at 87x, quite obvious in M46 with a mag11 star in contact to the NE; at 145x, this star gives the nebula a triangular shape but at 312x, its shape is better defined, quite round and diffuse; a faint star of mag14 is quite centraly located in the nebula, visible only briefly with averted vision [the real central star is much fainter]; slightly annular but the ring is more obvious at 145x with OIII, quite sharp edges.
Observer: Jeff Medkeff
Your skills: Advanced (many years)
Date/time of observation: Feb 23, 1998
Location of site: Rockland Observatory, Sierra Vista, Arizona (Lat +31.5, Elev 4550 ft.)
Site classification: Rural
Sky darkness: 6.3 Limiting magnitude
Seeing: 8 1-10 Seeing Scale (10 best)
Moon presence: None - moon not in sky
Instrument: 10" f/4.5 EQ
Magnification: Up to 355x
Description: At a variety of powers, including 355x, this is a smoky colorless and circular planetary nebula. Reasonably large and seems to have a darker area within its borders. There is a faint star (non-GSC) on its following edge, and a fainter one almost centered in the nebulosity. The neb appears almost annular, but if so, it is much thicker in the bright parts proportionally than M57 is.
This pn is easy to find; look at the north central part of M46.
Steve Coe, observing with a 13" f/5.6, notes: "Bright, large, elongated 1.2 X 1 in PA 135, the central star is easy at 100X. Raising the power to 440X brings out several dimmer stars involved in the nebula. Also at the higher power the shape of the planetary is seen to be an incomplete ring, somewhat like a horseshoe. This bright rim is about 270 degrees around and is dimmest on the north side. I have always seen this planetary nebula as light green in color."
AJ Crayon, using an 8" f/6 Newtonian, notes: "is the planetary nebula involved with M 46. It is 30"X20" 10m, in positon east of southeast and slightly brighter on the southeast edge with 3 stars involved, at 120X. This planetary is on north side of M 46. While here, don't miss M 46!"
[amastro] posting, Sat Nov 25, 2006
82" telescope, McDonald Observatory near Fort Davis, Texas, USA
f/13.7, 35mm Televue Panoptic (5' fov, 812x)
This planetary nebula in M-46 presented as a perfectly smooth and uniform ring with no discernable color to me. There were several stars involved in the nebulosity but none seemed to be in the exact center. The real target in this area, for me, was the Calabash Nebula, (OH231.8+4.2) 6.5 arc-minutes east and a little north (PA 79) of NGC 2438. Unfortunately, I left my detailed finder chart back in my room that first night, and the second night there were just too many objects left on the "must see" list to get back to this guy. Maybe next time... :-(
A 10-inch f/5 shows this nebula on the northern edge of the cluster, with a 10th mag star almost touching its eastern side. At 100x the planetary is very obvious, and the cluster itself is well spread out with large patches of black sky inbetween the stars. At 120x this pale gray nebula has a pretty large smooth disc, evenly illuminated with no central star. At 30x the planetary is not as obvious, appearing like a slightly defocused star. However, with some attention, it is readily seen.
6-inch f/8 Newt: "This planetary can be seen with attention using the 25mm eyepiece having an approx. 10th mag star close by; looking like a hazy appendage to the NW of the star. Using 4mm and 6mm eyepieces, the planetary is clearly shown as a pretty large regular patch, slightly elongated."
Sutherland (Huis Lana)
"Bertha" 12-inch f/4.8 Dobsonian (EP: 32mm, 25mm, 10mm, 6.3mm Plossls, 2x Barlow, 32mm Erfle)
Conditions: Clear, dark.
Join Sirius (alpha CMa) to Muliphen (gamma CMa) and continue on in that direction for twice the distance, and you land across the border into Puppis and in a field rich with open clusters. The most prominent two are NGC 2422 and NGC 2437 (Messier 46 & 47). Lurking on the outskirts of NGC 2437 is the planetary nebula NGC 2438. It is a large oval glow with a bright star appended. The elongation is in the direction of this star. In the centre of the nebula is a much fainter star. The nebula is brightest around the edges, growing slightly darker to the centre. (D: 20090123/24)
Date observed: 23/05/2004
Location: Boyden Observatory, Bloemfontein
Limiting Magnitude: 6
Transparency: Clean & Clear
Instrument: 13 inch refractor, 40 mm eyepiece, 15' fov
General impression of object: (done in conjunction with M46)
One of the more acceptable planetary nebulae through a medium telescopes, due to detail visible. It was a surprise to see the centre star (using slight averted vision). Rating: 8.5/10
General impression of its surrounding area: Probably the best area any bright planetary nebulae can ask for - in the open cluster M46! The area is a site and sight to behold.
Description of object:
[Telescope]: The nebulae are situated in the very impressive and large M46 open cluster, which gives it additional focus of attention. The nebulae itself appeared through the 13" as a faint cloudy (smooth) oval-rectangular object with an evident darker inner "circle region" in which a very small white star is situated, most probably the left-over star after the "explosion". It is visible using slight averted vision. No other characteristics were evident.
Remarks: (How good or bad the observation was and reasons)
The observation was done under adequate to good dark skies and weather conditions. (The centre star of the planetary nebulae may be an interesting item to test the quality of the instrument used and the observational conditions).
12-inch f5 (EP: 26mm SW, 20mm UW, 7mm UW)
Conditions: The most clear sky possible. Dark moon and stars magnitude 6 and fainter are visible with the naked eye. Excellent clean sky, limited star flickering and brilliant objects. Limiting Magnitude: 6.2.
Planetary nebula located in Puppis. Bright, Well defined and slightly oval. A tiny faint disk is observed at 214 magnification, greenish in colour. No central star seen.
Observing site: Little Bennett Regional Park
[7h 41m 48s, -14° 44' 0"] A small, bright, planetary on the edge of M 46.
The Messier objects
The Bennett objects
The Caldwell list
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