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Lacaille II.2 (4,604 of 18,816)

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Lacaille II.2

Lacaille II.2, Cl Collinder 140, C 0722-321, Cl VDBH 2, COCD 136, Tuft in the Tail of the Dog

RA: 07h 24m 26.7s
Dec: −31° 51′ 0″

Con: Canis Major
Ch: MSA:368, U2:361, SA:19

Ref: SIMBAD, DAML02, Archinal&Hynes (2003), Cozens (2008)

(reference key)

Type: open cluster, 33m

Mag: B=3.65, V=3.5

Size: 60′
PA: ?

Historical observations

Lacaille (1755)

Lacaille recorded an object which he described as: "Heap of 8 stars of 6th to 7th magnitude, forming to the naked eye a nebula in the sky."

His position (07h 26m 12s,34 07' 20", J2000.0) is close to a single 6th magnitude star (HR 2856, HD 59026), which is unlikely to appear as a naked-eye nebula.

However, 2.3 north lies the scattered cluster Collinder 140. Despite the co-ordinates being very different, Lacaille's description fits Cr 140 well, as Cozens (2008) also suggests. Cozens also remarks that Lac II.2 is noted in James Dunlop's records (microfiche #1100).

Published comments

Williams, P.M

An article published in MNASSA by P M Williams was entitled "The Open Cluster Cr 140": "Three colour photoelectric results are presented for 24 stars in the region of Cr 140. From these results and some photographic photometry the distance of the cluster is found to be about 360 pc [making it a foreground object between the Sun and the Orion Arm] and the age 23 million years from the brightest main-sequence stars." V magnitudes ranged from 5.34 to 10.95.

Modern observations

Tom Lorenzin

The electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "4M; 40' diameter; 30-plus members; large and sparse; great binocular object."

Steve Coe

Coe, using a 17.5" f/4.5, notes: "is a very large open cluster I have called The Tuft in the tail of the dog. There is a naked eye fuzzy spot at the end of the tail of Canis Major. I have found it to be an excellant area with the binoculars. It includes a wide double, Dunlop 47, which is 5.3 and 7 mag, sep 99 ", which I see as blue and light yellow in the telescope at 100X."

(IAAC) Steve Coe

Obj: Col 140, Dunlop 47 - Inst: naked eye, 10x50 binocs, 6" f/6 dob

From: Steve Coe [scoeandlross@sprintmail.com](via Lew Gramer)

Date: Tue, 06 Jul 1999 16:47:13 -0400

Observer: Steve Coe

Your skills: Advanced (many years)

Site classification: Rural

Moon presence: None - moon not in sky

Instrument: naked eye, 10x50 handheld binoculars, 6" f/6 dobsonian

Magnification: 1x, 10x, 100x

Filter(s): none

Object(s): Col 140 (Tuft in the tail of the dog), Dunlop 47

Category: Open cluster. Multiple star.

Class: III 3 p

Constellation: CMa

Data: mag 3.5 5.36m*, 5.3/7 size 42', sep 99"

Position: RA: 07:24, Dec: -32:11

Description:

I have an observation of Collinder 140, which I have called "The Tuft in the Tail of the Dog" for years. An obvious, naked eye grouping. It is at 7hr 24min and -32 12.

--

Col 140 is a very large open cluster I have called The Tuft in the tail of the dog. There is a naked eye fuzzy spot at the end of the tail of Canis Major. I have found it to be an excellent area with the binoculars. It includes a wide double, Dunlop 47, which is 5.3 and 7 mag, sep 99 ", which I see as blue and light yellow in the telescope at 100X.

Steve Coe

Brian Skiff

15cm - not distinctive as cl. BS, 25Feb1990, LCO.

Contemporary observations

Auke Slotegraaf

A 10-inch f/5 at 30x shows this off-beat cluster, with two bright members, lying in a very rich milky way field. It is a pleasing sight, and is sprinkled with stars 10th mag and fainter, having no apparent boundaries. On the northern tip of the cluster lies a wide, uneven pair of stars, about 8th mag; the south-eastern star is decidedly orange.

2002 June 20

2002 June 20, 20:00. 11x80 tripod-mounted. Stellenbosch Rifle Range site. First-quarter moon. Slight easterly breeze. Working on U 361.

Suspicious-looking coarse clustering of stars while sweeping. Six stars arranged in an obvious tick-mark shape (long axis SW to NE), having three bright, equal, stars, and three faint ones. The star at the flexing-point of the tick-mark (CD-314437) is the brightest. The star in the middle of the long arm of the tick (CD-314482) is orange (B-V = +1.07), and has a small companion close north-north-west.

The three brightest stars are CD-314437, CD-314454 and CD-314482.

My impression was that CD-314437 was the brightest in the grouping is evidently wrong; the two other bright stars are slightly brighter (V = 5.43 compared to 5.39 and 5.35).

Hoffleit & Warren, in "Preliminary Version of the Bright Star Catalogue, 5th Revised Edition" notes that CD-314437 is a member of Collinder 140.

CD-314454 is noted: "Also classified B2V, inconsistent with cluster photometry."

CD-314482 is called a "definite member Collinder 140" and a "Red giant of about 9 solar masses."

[2002-07-02: Interestingly, my obs may indeed have been correct regarding the stellar magnitudes; I noted that CD-314437 was the brightest tho the BSC5 showed it wasn't; according to the MSA, this star is a variable, NO CMa; perhaps it was near maximum when I made the obs.]

2002 June 20: Searching for Lac II.2

2002 June 20, 20:00 SAST. Stellenbosch (Paradyskloof Rifle Range). 11x80 tripod-mounted. First-quarter moon. Slight easterly breeze. Working on U 361.

(= Cr 135?)

RA 07:26:13, Dec -3408'54"

At Lacaille's position, in both the 13-mm aperture mask and (full) 80-mm aperture, all that is visible is a star, ~7th magnitude, flanked by two vvF stars.

Lacaille calls it "nebulous to the naked eye" - the bright moonlight doesn't enable me to confirm this; certainly at the position searched for, there is nothing naked-eye. However, Cr 135 could fit the description.

2002 July 02: Searching for Lac II.2

Stellenbosch (Paradyskloof Rifle Range)

11x80 tripod-mounted binoculars (12.5-mm aperture mask)

Conditions: Dark moon. NELM approx 5.0 at the pole. Immensely heavy dew.

Area at CMa/Puppis border along the Milky Way, southeast of the triangle of CMa. Lacaille's position (0726133408) corresponds closely to that of 5.9mag HR 2856 (CD-333813, 072642340827). Around this star, however, are merely two others, slightly fainter. There are similar "groupings" in the same binocular field. These three aren't particularly more impressive and there certainly aren't "7 or 8" stars here. The grouping isn't particularly easily visible with the naked eye I have seen it from Sutherland, but could not see it this evening (skies not very transparent nor dark at its present altitude). Within a few degrees, however, lie two naked eye "nebulosities" Cr 135 and Cr 140. Cr 135 is an obvious naked-eye patch. Pi Puppis is an apparent orange star to the naked eye, with a haze of unresolved starlight to the north. In good skies, this haze is seen as individual stars. Cr 140, about 5 to the north, is less obvious to the naked eye, and I haven't been able to see it as consisting of stars with the naked eye alone; it appears fuzzy. If Cr 140 is a challenge to the naked eye, then forget about looking for the grouping around HR 2856. In 11x80s, this is a coarse cluster of six stars. The brightest stars together look like a tick-mark, or rather more like an ornate old-fashioned smoking pipe, its bowl filled with 8-9th magnitude stardust, with a curved stem. In no way do I see Lacaille's "7 or 8" stars; a bit off to the north-east lie three more bright stars [HR 2881 (CD-30 4620, mv = 4.65), HR 2870/2871 (CD-31 4590, mv = 6.38) & HR 2873 (CD-31 4593 mv = 5.77)] that would readily make up "7 or 8" but they are rather distant this would make the grouping ~2 across how wide was Lacaille's field of view? Although Lacaille's position does "hit" a bright star (HR 2856), his telescopic description doesn't match the sky. Perhaps he was observing Cr 140? Jones [1969JBAA...79..213J] notes that Lac II.2 is "A group of 7 and 8 mag stars including h.3969." "h3969" is a double star, noted by John Herschel. The WDS-DM-HD-ADS Cross Index (Roman 1987) notes that "h 3969" is CD-34 3610 and CD-34 3611. Neither of these designations appear in the BSC5-R (Hoffleit & Warren 1991). The 1985 edition of the HD catalogue identifies these stars as HD 59100 and HD 59099, respectively, and lists the first of these stars at 1900.0 RA 0723.33406, mv = 6.75 [2000.0 0727.03418]. This double thus lies just south of HR 2856 discussed earlier.

2002 July 01: Searching for Lac II.2

Stellenbosch (Paradyskloof Rifle Range)

11x80 tripod-mounted binoculars (12.5-mm aperture mask)

Conditions: Dark moon. Slight easterly breeze. NELM approx 5.5 at the pole. Dew.

Five stars (one considerably fainter) in a line, oriented northeast-southwest. The four brighter stars are immediately noticeable because of their regular arrangement. There is another line of stars just to the north, almost converging on this one in the east, but the stars are much fainter, and less regular. Lacaille's description: I have no idea how he sees "seven or eight" stars!

Richard Ford

2013 February 8th, Friday

Location:Blesfontein Guest Farm,Sutherland.

Time:1:45am.

Sky Conditions:The most crystal 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.

Instrument:12-inch Dobsonian.

This open cluster is somewhat large as a condensation and that most of the stars in this cluster have faint and bright stars mixed together.The stars in this open cluster is well detached and that they are slightly concentrated towards each other.This open cluster measures 17'x 8.5'.Chart No.98,NSOG Vol.1.

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