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Type: planetary nebula
Mag: B=12.8, V=13.2
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Synonyms: H I-065
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "vB pL irregularly round, brighter in the middle like two nuclei."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "according to William Herschel, resolvable. Nucleus."
The NGC calls it "very bright, large, round, very suddenly much brighter in the middle to a nucleus, resolvable."
!! a star surrounded by vB, R, neb. 1' in diameter, from which proceed spiral arms.
Confirms HOB 15
The RNGC (Sulentic and Tifft 1973) notes that this is a 11.0 mag planetary nebula. Their coded description reads R,SMBM,HISB,))).
Journal BAA, 35, p159
modern photos show a planetary nebula, of peculiar double-armed spiral formation, with a surrounding faint ring about 80'' diameter and a central 10th mag star. Sir W Herschel's observation of resolvability was, therefore illusory.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part I. M.N.R.A.S., 35(5), 159.
Photo Index by Jim Lucyk: Sky&Tel. 5/66 p310, Sky&Tel. 5/87 p571, Sky&Tel. 7/69 p16 (drawing), Sky&Tel. 8/69 p84.
Houston calls this "an easy object for a 4-inch. The 10th mag nebula surrounds a 13th mag star, which is best seen with higher magnifications. ... the 4-inch Clark has never shown its 13th mag central star. At first this seems odd for a telescope with which I've reached 14th mag. However, the planetary's nebulous haze reduces contrast between the star and background, and maximum contrast is essential to achieve optimum performance from a telescope." Houston also called it "an easy 10th mag planetary with a 13th mag central star that many observers have trouble seeing. The trick is to use high power, which enlarges and dims the nebula and improves the contrast between it and the star. Pedro Cavanna of Norfolk, Connecticut, could not see the star with his 10-inch at 64x but found it 'easy' with averted vision and 133x."
Sanford calls this "one of the brightest large planetary nebulae in the sky, and sits just above the centre of the trapezoid of Corvus. It appears as a large (80 arcsec) round, featureless, gray-coloured object, with a fairly prominent 13th magnitude central star."
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "10.5M; 80" diameter; N-filter pops out nebulosity but knocks down 13M center star."
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 4361 (PK 294+43.1; PN G294.1+43.6; ARO 26, VV 62) Category: planetary nebula Constellation: CRV Object data: Vmag=109.9; Bmag=10.3; 81"x81"; type IIIa+II; central star of Vmag=12.8; discovered by Herschel in 1785; ELCAT: [OIII, 496+501nm] = 4 x [Hbeta, 486nm]. RA/DE: 12h24.50m, -18°47.6' (2000.0) Date and UT of observation: 06 February 1997, 18h30UT Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36) Site classification: rural, alt.1650m (5500ft) Limiting magnitude (visual in UMi): 6.2 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: 145-312x Filters used: OIII
Description: at 125x & OIII, medium to large PN, faint, homogeneous with very slight brightness increase towards the core, hard to tell if there is internal details; diffuse borders and mag13 central star easy to see; estimated diameter about 136".
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 4361 (PK 294+43.1; PN G294.1+43.6; ARO 26, VV 62) Category: planetary nebula Constellation: CRV Object data: Vmag=109.9; Bmag=10.3; 81"x81"; type IIIa+II; central star of Vmag=12.8; discovered by Herschel in 1785; ELCAT: [OIII, 496+501nm] = 4 x [Hbeta, 486nm]. RA/DE: 12h24.50m, -18°47.6' (2000.0) Date and UT of observation: 28 December 1990, morning 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: 36-100x Filters used: -
Description: at 36x, very small nebulous patch, quite faint with brighter center; at 72x, slightly brighter extended core, large PN in fact; at 100x, central star visible but comes and goes with the seeing.
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 4361 (PK 294+43.1; PN G294.1+43.6; ARO 26, VV 62) Category: planetary nebula Constellation: CRV Object data: Vmag=109.9; Bmag=10.3; 81"x81"; type IIIa+II; central star of Vmag=12.8; discovered by Herschel in 1785; ELCAT: [OIII, 496+501nm] = 4 x [Hbeta, 486nm]. RA/DE: 12h24.50m, -18°47.6' (2000.0) Date and UT of observation: 02 March 1992, morning 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): 3 Moon up (phase?): no Instrument: Meade SCT 8"/203mm f/10 Magnification: 87-312x Filters used: OIII
Description: at 87x, medium sized PN, very faint stellar center, very slight brightness increase towards the center, diffuse edges; quite round but somewhat elongated E-W; with OIII, just slightly better defined borders.
Steve Coe, using a 13" f/5.6, notes: "Bright, large, somewhat elongated (1.5 X 1) in PA 90, grey in color at 135X. The central star is obvious at all powers. Going to 220X brings out an almost "mottled" effect across the face of this planetary nebula, a strange effect for this type of object. Most planetaries I have seen appear smooth at high powers, this one does not."
:"This large planetary nebula is about 50" in diameter, and has an easily seen central star. The nebulosity is grey, and reminds me somewhat of the Owl Nebula in Ursa Major."
POSS: brtr part OX, elong ~E-W, brtr lobe on S also. m14 * 1'.65 NNW.
7cm - fairly f sm spot @ 30x. 50x: circ, somewhat brtr to center, but cen *
not obvious. m13 * S, m12 * SW. BS, 20Apr1993, Anderson Mesa.
15cm - lg & f. hard to keep in view at lox. annular neb, cen * suspected.
higher power helps somewhat.
- br modhisfcbr neb w/m13 cen * vis @ 50x. gradual contrast improvement
going from DS to UHC and [OIII] filters; no additional details
however. br part elong ENE-WSW, 1'.5x1'; vf ~circ halo fills in outside
flattened sides of brtr part on N&S. reaches halfway to m14.5 * NNW.
BS, 21Mar1989, Anderson Mesa.
25cm - cen * vis @ 112x, m13; surrounded by br area 40" diam. around this is
fntr oblong patch 60"x50" that extends more to S than N.
30cm - evenly br. f * on N. cen * seen. S side less br. circ, grey.
Hartung notes that although discovered by William Herschel in 1785, he did not recognize it as a planetary "as it is more hazy and less well defined than the usual type. It is a prominent round object about 45 arcsec across and white, with a clear central star ... only this star can be seen with a 3-inch but a 4-inch shows the hazy spot."
A 15.5-inch at 220x shows the planetary rather like a globular cluster through fog; the disc is diffuse, and the central star easy. Occassionally, this nucleus seems double? The disc appears mottled.
This planetary is an easy target for a 10-inch f/5 at 30x. It is remarkably easy to spot, and I noticed it as once whilst sweeping for it. At 30x, it appears very much like a small globular cluster; it is a round, diffuse, pale milky patch of light. Using the 10mm eyepiece for approx. 120 power, averted vision shows a bright, point-like nucleus, which may or may not be the central star. The same impression is noticed at 30x.
NGC 4361 - SEXTANS
Tel: 12" S/C –76x - 218x - Date: 1 Feb 2008 – Site: Alldays - good
In the heart of Corvus, this planetary stand its stake in a brilliant way. It appears to be a round shape galaxy at first sight. The nebula displays a strong bright middle 76x, and with higher power the central star 12.5 magnitude is seen with ease. With 218x the outer edge seems broken and haze away into the field of view. The field of view towards the north seems more busy with various magnitude stars than the southern part of sky.
Instrument:12-inch Dobsonian Reflector Telescope.
Sky Conditions:Dark moon and stars magnitude 6 and fainter are barely visible with the naked eye.
Transparency of the Sky:The most clear sky possible.
Seeing:Excellent clean sky,limited star flickering and brilliant objects.
Object Type:Planetary Nebula.
First Impression:This object looks like an out of focus star.
Chart Number:No.11(Extract taken out of "Atlas of the Night Sky").
Size:9mm Eyepiece:Field Of View:15'/6=2.5'.
7mm Eyepiece:Field Of View:15'/5.5=2.7'.
Size in Arc Minutes:2.6'.
Planetary Nebula is 2.6'*1.3'.
Brightness Profile:Towards the far outskirts of this nebula it is fainter while towards the central outskirts this nebula grows slightly brighter.
Challenge Rating:Difficult object.
By observing this planetary nebula at high power I have found that this nebula is sharply defined and faint as a large out of focus star.It looks almost bipolar in shape.It has a greenish surface.
Observing site: Pinnacles overlook
[12h 24m 30s, -18° 48' 0"] Faint, the central star was barely visible. It looks like a face on Sc galaxy through the 12.5mm Orthoscopic
Observer: Carol Botha
Location: Betty’s Bay
Instrument: 12 inch Dobsonian F5. Eyepiece: 25mm plossl (x 60 fov 50') 15mm plossl (x 100 fov 37') 8mm uwa (x180 fov 22')
Sky: Clear, just after (almost 1st quarter) moonset
Limiting mag: 5.66 6 Corvus
Dimension: 80'' x 80''
Planetary Nebula in Corvus.
Easy to locate. NGC 4361 forms a triangle with Gamma and Delta Corvi
Viewfinder: The planetary should be nesting in the hollow formed by two prominent triangles joined by a semicircle of stars.
25mm: A small bright greyish smudge visible
15mm: The smudge appears much brighter
8mm: bingo – central star!
The Messier objects
The Bennett objects
The Caldwell list
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