Blue Flash Nebula

Image gallery

Historical observations

William Herschel (c.1784)

Synonyms: H IV-016

William Herschel observed it in 1784 with his newly completed 18.7-inch f/13 speculum telescope. He called it "perfectly round, pretty bright, and pretty well defined; about 3/4 min. in diameter." and also "pB, perfectly round, pretty well defined, 3/4' diameter, resolvable."

Lassell, W. (1866)

Bibcode: [1866MmRAS..36....1L]

Sketched and described.

Burnham, S.W. (1894)

Burnham, S. W. () "Measures of planetary nebulae with the 36-inch equatorial of the Lick Observatory", Pub. Lick Obs., vol 2, p159-167. "A measure of the diameter of this nebula in the direction of the 10m star gave 39.1''."

Webb, T.W. (1893)

In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "small, faint, misty, ill-defined, closely surrounded by several small stars. E. of Rosse, spiral."

Published comments

Doig, P. (1925)

Journal BAA, 35, p159

Planetary; main part 44'x37'', with faint cone-shaped ansae; central star 124th mag visually (Burnham) ... the complicated structure on photos accounts for Lord Rosse's idea of spirality.

Doig, P. (1925)

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.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 12.0 mag planetary nebula.

Photo index

Photo Index by Jim Lucyk: Sky&Tel. 9/83 p277, Sky&Tel. 10/69 p227, Deep Sky #11 Su85 p9, Deep Sky #15 Su86 (inside front cover) & p8, Deep Sky #20 Fa87 p12, Deep Sky Monthly 2/82 p9, Astronomy mag. 9/87 p102.

Modern observations

Sanford (1989) Observing the Constellations

Sanford notes that this planetary nebula in Delphinus is elliptical and has diffuse edges.

Walter Scott Houston

Houston notes that this planetary is situated in a coarse clustering of stars. Listed at 12th mag, he notes that it is more conspicuous than nearby 12th mag stars. He notes that it is relatively easy for a 6-inch under good skies.

In 1976, Houston called this "a tempting planetary. Because its diameter is only 0.7', at low power it is difficult to distinguish from a star. The total light is about mag 10.5 and the surface brightness is about a quarter that of the Ring Nebula. NGC 6905 has a central star of about mag 14, requiring a 12-inch or larger to see."

Hartung, E.J. (1968) Astron.Obj.South.Tel

Hartung notes: "In a well-sprinkled star field is a rather faint bluish somewhat elliptical nebula about 45 arcsec across, between two stars close north and south with other stars near; the edges are rather diffuse and the light is mottled with no visible central star. The nebula is shown with 15cm and dimly with 10.5cm."

Steve Coe

Steve Coe, observing with a 13" f/5.6, notes: "Bright, pretty large, elongated 1.5 X 1, central star easy at 100X. Moving up to 270X with a Barlow lens reveals that the east and west sides are brighter than the rest of the nebula. This planetary is pale green at all powers. I have heard NGC 6905 called the "Blue flash nebula" but I have never seen blue in this object."

Wilson, Barbara

Barbara Wilson of Houston, Texas, reports seeing a lot of internal structure with a 20-inch reflector.

Hogsten, Scott (IAAC)

(IAAC) Obj: NGC 6905 (Blue Flash Nebula) - Inst: 12.5" f5 Dob

Observer: Scott Hogsten

Your skills: Intermediate (some years)

Date/time of observation: Aug. 27, 1998 23:30 EDT

Location of site: Perkins Obs. Delaware OH (Lat , Elev )

Site classification: Suburban

Sky darkness: 4.7 Limiting magnitude

Seeing: 6 1-10 Seeing Scale (10 best)

Moon presence: Minor - crescent or far from object

Instrument: 12.5" f5 Dob

Magnification: 110x, 150x, 220x

Filter(s):

Object(s): NGC 6905 (Blue Flash Nebula)

Category: Planetary nebula.

Class:

Constellation: DEL

Data: mag 12.0 size 44"x38"

Position: RA 20:22 DEC +20:06

Description:

Small and brighter than the magnitude suggests. The planetary is nicely situated is a triangle of stars. I easily picked this out at 110x. Jumping to 220x showed a hint of a annular appearance with averted vision. This effect much like a blinking planetary only in this case the annularity blinked in and out.

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Gross, Todd (IAAC)

Observer: Todd Gross Your skill: Intermediate - Many years Date and UT of observation: 7/11/99 07:15 GMT Location & latitude: 22 mi. West of Boston, Ma. 42.3N Site classification: Suburban Limiting magnitude (visual): approx. 5.0 zenith, same object Seeing (1 to 10 - worst-best): 5-6 Moon up (phase?): No Weather: Clear Instrument: 18" f/4.2 fl=1925mm Newt Magnifications: 320x (binoviewer), 320x, 443x Filters used: UHC at times Object: NGC6905 Constellation: Sagitta Object data: Planetary Size(s): 40" Position:20:22RA 20:07n Magnitude: 10.9 Personal "rating": B+ !

Was this supposed to look so good? Once in awhile I stumble upon a nebula that is much better than I had expected. The blue flash nebula is a bluish tinted round planetary that sits in a rich field of stars. As soon as I applied magnification.. it's goblin-like face became apparent, particularly with averted vision. It's central star becomes very visible at 320x, and above, and looks like a nose. Two symettrical wide triangles pointing in towards the central star appeared o form "eyes" , particularly since they were darker on the top 1/2 of each (south was up) Reminiscent of the owl nebula. View through the binoviewer was similar, but the splitting of the beam robbed a bit of color from the object, otherwise much the same.

thanks! -Todd

Boston Meteorologist Todd Gross

toddg@weatherman.com

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "12M; 40" x 35" extent; oblong bluish blob; soft and small."

Birkmann, Mark [amastro]

Observer: Mark Birkmann Your skills: Intermediate (some years) Date/time of observation: 7/9/99, 6:15 UT Location of site: New Haven, Missouri (Lat N 38, Elev ~700') Site classification: Rural Sky darkness: 5 1-10 Scale (10 best) Seeing: 5 1-10 Seeing Scale (10 best) Moon presence: None - moon not in sky Instrument: 30" f/4, dob Magnification: 150x-540x Filter(s): Object(s): NGC 6905 Category: Planetary nebula. Class: 3+3 Constellation: delphinus Data: mag 11.9p size 42"x84" Position: RA 20h:22m 23s DEC +20:06' 16"

Description: This bright pn is located in a beautiful star field. It appeared round, gray/green, evenly illuminated, and the mag 15.7 central star was held steadily with averted vision.

Ware, Donald J

"Another fine planetary nebula, this silver-grey puff of light is about 30-40" in diameter, with a slightly brighter center and somewhat diffuse edges. It is nicely framed by a triangle of stars."

Brian Skiff

= HD193949 = PK 61- 9 1

Marling: mv=11.1

POSS: 1'.35 btwn *s on W side of rectangle, implies 15cm diam of 45"-50".

6cm - vis in 30cm finder, discernable from a *. CBL, 31Aug1975, Roof.

15cm - mod f, seen @ 47x. 122x shows it in triangle. roughly circ, diffuse edges, even light. nice. HHM, June 1977, Roof.

- consp glow w/o filters @ 80x, still has good [OIII] enhancement. at 165x the familiar rectangle of *s shows well w/neb on W side. circ, 40" diam: fills two-thirds length of W side of rectangle. sfc seems somewhat mottled, vsl brtr across center. cen * very occas pops out w/averted vis, however not a reliable detection. BS, 15Jun1988, KPNO.

25cm - vlg @ 238x. cen * evident. not homogeneously br. BS, 20Jul1974, Big Cypress.

- much lower sfcbr than N6891. lg disk 40" across, grows brtr to center where f sparkle can be seen @ 190x. blocked in on N&S by *s: N is m11, S is m12. sketch in card file. BS, 6Jun1981, Slate Mtn.

30cm - unevenly br @ 238x, elong nearly N-S by 15%. cen * vis. CBL, 31Aug1975, Roof.

Contemporary observations

Magda Streicher

22 August 1998

22 August 1998, Farm site, Meade 8" with a 18mm wide angle & 26mm Plossl, 36' fov, Sky Conditions: Clear 7 to 8 magnitude

Very small and faint, roundish shade, surrounded by faint tight stars.

Richard Ford

2009 September, 19h

Location:Perdeberg.

Instrument:12-inch Dobsonian Reflector Telescope.

Sky Conditions:The fainter parts of the Milky Way are barely visible.

Transparency of the Sky:Haziness only visible on the horizon.

Seeing:Atmosphere stable with little interference.

Limiting Magnitude:4.9.

NGC 6905

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Object Type:Planetary Nebula.

First Impression:This object looks like a planetary nebula.

Location:Delphinus.

Time:8:15pm.

Chart Number:No.7(Extract taken out of "Atlas of the Night Sky").

Brightness:Magnitude 12.

Overall Shape: This planetary nebula has a slight annnular shape at 214 magnification.It is well defined and slightly oval.

Brightness Profile:From the far outskirts of this nebula it grows brighter in the middle.

Challenge Rating:Fairly easy to observe in a large telescope under dark skies.

Is a disk seen? no.

Is the edge sharply defined? No.

What colour is the nebula? Pale Green-White.

Is there a central star? No.