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epsilon Orionis Nebula

NGC 1990, Ced 55h, LBN 205.42-17.78, LBN 940, epsilon Orionis Nebula, V 34, h 363, GC 1193

RA: 05h 36m 12.7s
Dec: −01° 12′ 7″

Con: Orion
Ch: MSA:254, U2:226, SA:11

Ref: NGC/IC

(reference key)

Type: unverified

Mag: B=?, V=?

Size: ?
PA: ?

History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

NGC 1990. In spite of this nebulosity having been "seen" by WH, JH, and Dreyer, as well as by several amateurs in recent years, there is no trace of it on any photograph of the area. JH suggested that the nebulosity extends at least 12 arcmin north and south of Epsilon Orionis, while Dreyer makes it more extensive to the south. (On the POSS1 red plate, the star is apparently close to the center of an extended, striated nebulosity. This, however, is not visible on any other photo, including several color photos that would certainly show a red nebulosity if it existed. This striation is a defect on the red plate, apparently caused by imperfections or reflections in the red Plexiglass filter.)

It is just possible that this may be another case like IC 349 (which see) which is so close to Merope as to be not easily imaged. Until Eps Ori is imaged in such a way that the star can be removed to show the nebulosity that the Herschels and Dreyer claimed to have seen, I have no choice but to call NGC 1990 an illusion.

Also see NGC 7088 for another well-known case of an illusory nebula "seen" by many experienced observers.

Historical observations

William Herschel (c.1784)

Synonyms: H V-034

Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He wrote "I am pretty certain Epsilon Orionis is involved in unequally diffused nebulosity."

Birr Castle/Lord Rosse (1850)

The Earl of Rosse, observing with a 72-inch f/8.8 speculum telescope, recorded it 6 times and noted "Nov 30, 1850. The luminous appearance extends about 15' all around the star."

NGC/IC Dreyer (1888, 1895, 1908)

The NGC describes it as very remarkable, extremely large and elongated, with Epsilon Orionis involved to the west. Dreyer calls it a nebula of the Merope class, and observed it at Armagh in 1886, noting: "the star is in the north west end of the much elongated nebulosity of which the north east border seems sharper than the south west one."

Published comments

Pickering, E.C. (1890)

Detection of new nebulae by photography. Annals Harv Coll Obs., 18, 113. Bibcode: [1890AnHar..18..113P]

Photographs taken with the Bache telescope, a photographic 8-inch f/5.5 doublet, covering 10 degrees square, were examined by Mrs M Fleming with a magnifying glass.

"Including epsilon Orionis. Suspected on [Plates] 2312, 2325 and 2335; not contained on 2423."

Cederblad, S. (1946) [VII/231]

Ced 55h (NGC 1990)

Position (1900): RA 5 31.1, Dec - 1 16

Star: 1 969 (Mp=1.45, V=1.75, SpT=B0)

Spectrum of nebula: emission spectrum (inferred from sp.t. of exciting star)

Classification: Neb associated with mainly one star (which may be multiple) - star surrounded by a neb envelope without conspicuous structure (eg. lambda Scorpii)

Size: 50'x50'

Notes: "Ced 55 h = NGC 1990 = GC 1193 = h 363 = H V 34. Disc. 1786. WP 166. (114, 209, 216, 282, 310, 316, 578, 631). R. The nebula around {eps} Orionis = -1 969 = HD 37128 = Boss 6960. Ced 55: The Orion region. History and bibliography: (118, 119, 186, 188, 191, 276, 352). The nebulous groundwork and the exterior nebulosities: (20, 21, 26, 53, 58, 78, 142, 143, 186, 191, 206, 207, 278, 279, 281, 282, 289, 305, 312, 438, 480, 519, 540. 541, 593, 594, 595, 620, 625, 628, 630 Pl 34, 663, 675, 715, 726 No 41, 769, 782, 802, 818). R. It is shown on several photographs, e.g. (630) Pl 34, that the whole region of the constellation Orion is filled up by vast masses of nebulosity. As is well known, there are several condensation which seem to stand out from the general background, and which have been separately discovered and studied. Such subnebulae, will be individually discussed below. Taken as a whole, No 55 of the catalogue should be classified as C. 2 in addition to the separate classes of the subnebulae."

Lynds, B.T. (1962)

Lynds, B.T. (1962) Catalogue of dark nebulae. Astrophys.J.Suppl.Ser. 7, 1-52. [also: computer datafile: VII/7A]

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a diffuse nebula. Their coded description reads NF DC.

Modern observations

[amastro] NGC 1990

Gentlemen;

I cannot be any further help on this object until I get a change to re-observe it. Maybe if the clouds will EVER go away--next millenium???

I used Bellatrix as a reference star to see if there was any condensation on my eyepiece and consistently saw a glow around E ORI that was not around Bellatrix. Now, my mirror does NOT have a turned edge and I would be very careful about impuning the optics of fellow observers. Let's not turn this into an s.a.a. discussion with people posting the fucaultgrams (sp) of their mirrors. Steve Coe

------------------------------------------------------------------------

The question whether NGC 1990 exists or not has been raised from time to time over the past several years, but there continue to be divergent views, with some experienced observers reporting observations of the object and others returning negative reports. Can contributors to this group shed any more light on this issue? The object is on the Herschel II list, and the authors of the list defend its inclusion by reference to an observation with a C11, reporting that the nebulosity surrounds epsilon Orionis and looks like the reflection nebula in the Pleiades, only fainter and more diffuse. W Herschel reported observing the object on Feb. 1, 1786, but his comment on the observation reflects some equivocation about its existence. He wrote: "I am pretty certain e Orionis is involved in unequally diffused nebulosity." J Herschel reported seeing the object, and I have seen more recent positive reports from Steve Coe and Jay Freeman (although I believe Jay reported seeing only a small v-shaped bit of nebulosity south of epsilon.) Many others have reported seeing nothing there and have expressed skepticism about the existence of this object. The nay-sayers, as far as my records show, include Steve Gottlieb, Brian Skiff, and David Knisely (please correct me if I have put anyone in the wrong camp). I made a good effort recently from a dark site with a 15" and failed to see anything but scattered light from the star and the product of condensation on my optics. I am tempted to call this one the "turned edge nebula" and give up on trying to do all 400 of the Herschel II. Any insight on this one? Cheers, Bill Bryson

-----------------------------------------------------------------------

See Harold Corwin's discussion under the "puzzle solutions" list for the appropriate batch of NGC numbers starting at: http://ngcic.org/corwin/DataFiles/ngcbugs_1.txt Note also that other 19th century observers saw nothing with large telescopes when using an eyepiece with an occulting bar to block the light of epsilon Ori.

\Brian

------------------------------------------------------------------------

Re: does NGC 1990 exist? My observations with both my 8 inch (which I "loggged" NGC 1990 during my Herschel 400 program), and now my ten indicated that all I probably logged was mainly just scattered light. I see no defined "squarish" edge (as plotted in Uranometria) to anything within half a degree of Epsilon (just a symmetric glow getting brighter towards the star), and using the Digital Sky survey images and doing some processing, I was unable to determine whether there was something there or not. The images merely showed an increasing glare as you get closer to the star, which tends to match the scattered light profile of other similarly-bright stars in other areas of the sky. The 1st edition of Sky Atlas 2000.0 does plot it, but NGC 1990 is not present on the 2nd edition, although it is on Uranometria. I have seen a few plates of the area, but none really answer the question definitively. I guess that puts me in the "probably not" category. However (with tongue firmly planted in cheek), NGC 1990 is probably the easiest entry on the Herschel 400 to log, since it is visible in *any* telescope which can show Epsilon Ori and which scatters light! :-). Go ahead and log it (the Herschel people deserve it, as they put in a couple of other ringers in the Herschel II listing). Clear skies to you. --

David Knisely KA0CZC@navix.net

------------------------------------------------------------------------

] I believe Jay reported seeing only a small v-shaped bit of

] nebulosity south of epsilon...

That's right, and if I recall, it was pretty marginal. I will check my log when I am home and post again if we have both remembered incorrectly. There is some stuff on deep images in that area, and I went looking for it specifically; it's not nearly as convincing as if I had examined the area first and then compared what I saw with images.

I have also logged what appeared to be weak symmetrical glow about epsilon, but I know of no convincing way to distinguish a weak symmetric reflection nebula about the star from a weak symmetrical reflection nebula on the objective (dew), in the sky of Earth (cloud), or in the observer's eye.

-- Jay Freeman

PS: "Turned-Edge Nebula" is an excellent title, but before we give it precedence for this one specific object, perhaps we should consider naming a class of objects, for surely there are more. E.g.,

TE 1 == NGC 1990

TE 2 == ...

------------------------------------------------------------------------

Here is a transcription of my logbook notes for my observation of something in the vicinity of NGC 1990.

I was observing on December 11/12 1998, from Fremont Peak State Park, near San Juan Bautista, California, with my Celestron 14 at 98x (40 mm Vernonscope Erfle). Stuff in [] added tonight for elaboration. At the location of "NGC 1990", see a wide, flat "V" of nebulosity, open to the north, about 20 arc-minutes sw of [epsilon handwritten as a Greek letter] Ori, best with [Orion narrow-band LPR] Ultrablock. I recorded no specific notes about conditions, but there are some remarks about other objects that are indicative: I tried to split Sirius at 252x, and failed, and noted "Seeing is not that good anyway." I saw six stars in the Trapezium; that is, A-F, at 252x. I could see the Horsehead at 98x without any filter, but commented "Ultrablock improves the view a lot". And I saw several patches of S 147, both without and with the Ultrablock. The patches seen were at plotted positions for some of its filaments. I logged the Christmas Tree Cluster, NGC 2264, as "well resolved, and filled with and surrounded by nebulosity," also at 98x. All this means that it was quite a good night.

Whatever it was that I saw, it was certainly not the star-enveloping nebulosity reported by earlier observers; thus this observation provides no evidence whatsoever of NGC 1990 in the strict sense. I cannot rule out glow from a chance distribution of stars too faint to see. I think I remember double-checking this observation with the DSS plate that I had checked beforehand, and concluding that whatever I saw for sure did *not* appear to be on that plate. Thus if it was nebulosity, it would have been something at a wavelength to which the DSS plate was not sensitive.

-- Jay Freeman

------------------------------------------------------------------------

I found the exchanges about NGC 1990 from last year. This pretty much closes the book on this non-object. Since the collected goodies (including the details of the 19th C observations and references to specific modern photos reaching to low surface brightness) run to some hundreds of lines, I've copied the file out to the Lowell ftp area rather than sending to this list: ftp://ftp.lowell.edu/pub/bas/deepsky/n1990.out \Brian

------------------------------------------------------------------------

Retrieved from [ftp://ftp.lowell.edu/pub/bas/deepsky/n1990.out]:

Folks,

Since I started this controversy, I've been looking into a bit more, and continue to find precious little evidence that there's anything centered on epsilon Orionis.

Some historical comments: this is a Herschel discovery, and Bigourdan mentions that neither he nor D'Arrest nor Engelhardt saw anything convincing here. (Harold will presumably provide a more complete translation of Bigourdan's description.) The NGC position matches epsilon Ori exactly. Dreyer's note in the back of the NGC suggests he observed it also. The NGC code description indicates an elongated object, and Dreyer's comment about it being a Merope-type object make it sound as though it was fairly easy to see.

Jay Freeman, in response to my query, comments that what he saw _was_not_ a glow centered on epsilon Ori, but instead the smaller, well-defined amoebas off to the west and southwest about 20'-30'. Although I am not sure but what his may be the first visual observations of these blobs, they are clearly _not_ NGC 1990. Coe, Kniseley, and Kepple (in a published sketch with a 30cm telescope---I said in error this was Glen Sanner previously) all claim to have seen circular diffuse glows centered on epsilon Ori similar in brightness to the part of IC 434 near the Horsehead.

In his comments Jay noted that he probably made the assumption that the glows he did see were merely the outer fringes of what was probably a large nebula centered on epsilon, but lost due to scattered light. This brought to my mind the suggestion that maybe the 19th Century observers (well, apparently only W. Herschel in the 18th Century!) could have assumed the same thing. There may not be enough detail in the source material to justify this, but perhaps Harold and Steve G. have a better feeling for it. Perhaps the elongated shape given in the NGC refers to this, i.e. a mispercieved glow with epsilon Ori at its head, and trailing off to the west, where the real nebulae are.

Besides the POSS-II F (red-light) film, which is relatively free of scattered light, my best evidence so far on the non-existence of NGC 1990 is a greatly contrast-enhanced wide-field image in Malin & Murdin's "Colours of the Stars" (the mid-80s book, not the recent, wherein Malin has shed all his coauthors). This black-&-white image shows the IC 434 region completely burned-out, and the broad swath of nebulosity the spreads west of it quite brightly. There is no nebula around epsilon Ori on this image. Farther southwest from epsilon, making a flat triangle with delta Ori, is a general increase in nebulosity associated with the blobs mentioned above. These are not NGC 1990 either.

Imaging the field well will probably require a sharp refractor or high- end telephoto (to minimze scattered-light problems) with a CCD. This will need to reach well down into the sky background, specifically below mag. 25 per square arcsecond in surface brightness (faint stellar limits are irrelevant---you need fast f/ratio, not aperture for this task).

\Brian

Date: Mon, 4 May 1998 15:59:58 -0700 (PDT)

From: Jay Reynolds Freeman (freeman@netcom.com)

To: bas@lowell.edu

Subject: Re: NGC 1990

When I asked the DSS to give me the position of NGC 1990, from "SIMBAD", it reported 05 34 31.775 / -01 38 3.375. I retrieved a 30-arc-minute image therefrom, which showed no enormously bright star, so I asked it for epsilon Orionis's position, and got 05 36 12.751 / -01 12 6.948, which is a little different. (Don't you just love positions of amorphous blobs to 0.001 arc-second?) The SIMBAD position for NGC 1990 is in fact not far from the SE edge of the blue blobs. The two 60-arc-minute images overlap considerably.

My observation would have been entirely consistent with seeing just the aforementioned blue blobs, which I may have hastily interpreted as the irregular periphery of a large nebula more nearly centered on epsilon. I was certainly looking at epsilon and the nearby field, without regard to what SIMBAD does or does not think is the position of NGC 1990. But that field included the blue blobs.

Is the POSS itself (-I or -II) available on the web?

Ruling out the existence of a faint nebula centered on epsilon may be very difficult.

-- Jay Freeman

From: hgcjr@ipac.caltech.edu

Date: Tue, 5 May 1998 13:17:58 -0700

To: bas@lowell.edu, dk84538@navix.net, freeman@netcom.com,

hgcjr@ipac.caltech.edu, scoeandlross@sprintmail.com,

sgottlieb@telis.org

Subject: Re: Current state of NGC 1990

Hi, folks,

Just a short note to fill in some additional bits of the history.

] Some historical comments: this is a Herschel discovery, and Bigourdan

] mentions that neither he nor D'Arrest nor Engelhardt saw anything convincing

] here. (Harold will presumably provide a more complete translation of

] Bigourdan's description.)

]From Bigourdan's "Observations ..." 5 hour zone: "I could not see any trace of nebulosity around this bright star which is epsilon Orion. Nor did d'Arrest or Engelhardt see any nebulosity around this star."

D'Arrest's notes are in German, which I don't know: "Von dem grossen Nebel, der diesen hellen * umgiebt, ist im Fraunhofer keine Spur zu erkennen der Himmelsgrund ist, wenn der * hinter den Ringen steht, in der Nahe ebenso dunkel, als sonst in dieser Region." (23 Aug 1855).

I don't have Engelhardt's monograph, but here are the two Herschel's observations.

William Herschel's single observation reads: "1786 Feb 1. I am pretty certain epsilon Orionis is involved in unequally diffused nebulosity."

John Herschel's observation from sweep 107 (1827 Nov 23) reads: "Epsilon Orionis. Place by Catal[ogue] a v brilliant * involved in an immense nebulous atmosphere, whose n and s limits are 91 deg 7 min 29 sec and 91 deg 31 min 29 sec. Viewed also and shown to Mr. Dunlop in sweep 110 [1827 Dec 16]."

The 1830 position of the star is 05 27 35.370, -01 19 03.69, so JH's northern and southern limits correspond to about 12 arcmin on either side of the star.

In full, Dreyer's NGC note reads: "A nebula of the Merope class; the star is in the np end of the much elongated nebulosity of which the nf border seems sharper than the sp one (Armagh, 1886)."

Unfortunately, neither JH nor Dreyer gives enough information to let us work out whether their observations are accordant or not. In any event, there is no certain nebulosity on modern plates that would match either observation.

Best to all,

Harold

From: hgcjr@ipac.caltech.edu

Date: Tue, 5 May 1998 14:31:00 -0700

To: bas@lowell.edu

Subject: Re: Current state of NGC 1990

Hi, Brian,

I'll ask Wolfgang to translate the d'Arrest, but poking at the words makes it look like he put the ring of his ring micrometer over the star and still couldn't see anything in the field. It looks to me like your work has nailed the coffin lid on this one. I'll change my files. Thanks!

Harold

Folks,

We got a new batch of POSS-II J films in the library yesterday, and lo and behold, it includes the 5h40m/+0 field that contains the Belt of Orion. The fuzz around epsilon Ori is completely burned-in as expected, and at least for any nebula close to the star, the film is useless. The larger glow is clearly strictly from scattered light, since it is perfectly circular and has an utterly uniform texture, whereas every other (celestial) nebula on the plate has quite a lot of structure. The similar glow around delta Ori is indeed weaker, but this results both because the star is 0.5 mag. fainter (not much difference to your eye, but that's less than half as much light hitting the plate!) and because it is in the vignetted region of the plate.

\Brian

Date: Wed, 6 May 1998 19:31:55 -0700

To: hgcjr@ipac.caltech.edu, bas@lowell.edu, dk84538@navix.net,

freeman@netcom.com, hgcjr@ipac.caltech.edu,

scoeandlross@sprintmail.com

From: Steve Gottlieb (sgottlieb@telis.org)

Subject: Re: Current state of NGC 1990

Harold recently summarized the observations of N1990 from Bigourdan, d'Arrest (in German), William and John Herschel. In addition here are the published observations of the N1990 region from Lord Rosse's "Observations of Nebulae .." in 1880. The field was observed at Birr Castle on 7 occasions. I also checked Cederblad's extensive bibliography from 1946 in "Studies of Bright Diffuse Galactic Nebulae" and as usual he has quite a number of references if anyone wants to delve further for visual or early photographic sources.

Steve G

********************************************************

30 Nov 1850:

epsilon Orionis. The luminous appearance extends about 15' all round the star.

24 Jan 1852:

A B* of 7 mag. f about 75', with a pretty strongly marked neby. round it. (This would require verification, as it clouded immediately).

25 Jan 1852:

I think the atmosphere suspected last night round the * f epsilon Orionis exists, but as the speculum gave same appearance to some other stars, though in less degree, I am doubtful. [This * is probably B.D. -1 1004, 6.2^m, 4m38s f, 5'12" n of epsilon Orionis].

18 Feb 1874:

No nebula about epsilon Orionis (Lord R. and C., 3 foot Herschelian telescope).

27 Jan 1878:

No nebulosity seen. [Compare d'Arrest, "Resultate" p. 316].

Date: Thu, 7 May 1998 17:51:19 -0700

To: hgcjr@ipac.caltech.edu

From: Steve Gottlieb (sgottlieb@telis.org)

Subject: Re: Current state of NGC 1990

Cc: bas@lowell.edu, dk84538@navix.net, freeman@netcom.com,

hgcjr@ipac.caltech.edu, scoeandlross@sprintmail.com

At 1:17 PM -0700 5/5/98, hgcjr@ipac.caltech.edu wrote:

]D'Arrest's notes are in German, which I don't know: "Von dem grossen

]Nebel, der diesen hellen * umgiebt, ist im Fraunhofer keine Spur zu

]erkennen der Himmelsgrund ist, wenn der * hinter den Ringen steht, in

]der Nahe ebenso dunkel, als sonst in dieser Region." (23 Aug 1855).

For what it's worth, folks, here's the translation of Heinrich d'Arrest's negative entry for h363 = NGC 1990 (courtesy of a German instructor at my school):

"epsilon Orionis. Regarding the large nebula which surrounds this bright star, therre is no evidence in the Fraunhofer [refractor]. The sky background in the vicinity, if the star was behind the [micrometer] rings, is just as dark as otherwise in this region."

Steve G

=end=

From freeman@netcom.com Thu Oct 29 15:35:20 1998

Date: Thu, 29 Oct 1998 14:34:09 -0800 (PST)

From: Jay Reynolds Freeman (freeman@netcom.com)

To: bas@lowell.edu, dk84538@navix.net, freeman@netcom.com,

hgcjr@ipac.caltech.edu, scoeandlross@sprintmail.com,

sgottlieb@telis.org

Subject: An image that might show NGC 1990 is not there, at least in red...

Content-Length: 3969

The other day I ran across a lovely red-filtered 2415 exposure of the central part of Orion, by John Gleason, that is pretty convincing about the non-existence of NGC 1990, at least, in red. I put some text about it in a recent posting on sci.astro.amateur, but I am not sure you all bother with that newsgroup, so will repeat here...

########

After a summer reprieve from El Nino, gloppy weather returned to the California Coast on the weekend of October 23-24, 1998, as the onset of a front dropped half an inch of rain in my back yard, and put an end to hopes of Friday observing. A clearing trend and satellite images of a dry air mass suckered a few people out on Saturday, but I found Fremont Peak practicing for Hallowe'en, with fog dense enough that I could neither see the incandescent lights in the observatory building at less than a hundred meters, nor verify for sure that the brush rustling near the side of the path was merely wild pigs.

I have been a life member of the Fremont Peak Observatory Association almost since its inception, but have never checked out on its Challenger telescope, a 30-inch Newtonian on a cross-axis equatorial mounting. There are other benefits of membership, however, for the room adjacent the roll-off roof area where the telescope sits is lighted and somewhat warmer than the soggy outside. Several of us sat there for a few hours, eagerly awaiting clearing skies.

We had no luck with the weather, but as I wistfully wished for stars, my eye was drawn to some of John Gleason's magnificent astronomical photographs, framed and mounted on the walls. The prints in question were of negatives obtained with a Celestron Schmidt camera, whose enormous photographic speed made possible the use of fine-grained but very slow 2415 film. The images were obtained about a decade ago: John had used the red-sensitive emulsion in connection with a deep red filter to produce wonderfully detailed photographs of nebulous areas that emit in the red hydrogen line at 656.3 nanometers. One of them included the location of an object of noteworthy interest.

The photo showed the region of Orion's belt, south almost to the Orion Nebula. In this wonderfully well-exposed print, IC 434, the emission nebula against which the Horsehead Nebula appears in silhouette, is burned in white. Details in the Horsehead show up well, though the object is small. All of the nebulae on the relevant page of the _Millennium_Star_Atlas_ are easily identified, except for one, though a few are faint, perhaps because they are reflection nebulae without especially bright red emission. There is lots more, too -- for example, the entire periphery of the great oval HII region about sigma Orionis is outlined in white, and there is visible nebulosity across most of its interior.

What's missing is NGC 1990, the sprawling amoeba frequently charted as roughly centered on epsilon Orionis. The photographic process has widened the image of epsilon considerably, but not nearly as wide as the nebula is usually depicted -- for example, in _Millennium_ itself. I cannot be sure that there is no nebulosity in the area -- and indeed, there are a few tiny wisps and curls here and there near epsilon, mostly south and west of the star -- but there is nothing like the conventional fat blob, at least, not in red, down to well below the brightness levels of even the faintest parts of IC 434. Brian Skiff has mentioned wanting a photograph to point at to show the non-existence of this object, and at least in red light, this one of John's is the closest thing I have seen.

...

What is particularly embarrassing is that I *own* a copy of this print, and it is hanging on my wall in my living room, but I did not think to look at it when some of the previous EMail discussion of NGC 1990 was going on...

-- Jay Freeman, freeman@netcom.com

------------------------------------------------------------------------

Steve Coe

Steve Coe, using a 13" f/5.6, notes: "Very faint, large, irregularly round, more easily seen with Epsilon out of the field of view, but never obvious at either 100X or 150X. I compared this nebulous star to Bellatrix, a star with no nebulosity, to see it light clouds or condensation on the eyepiece influenced my observation of nebulosity around Epsilon. There was always some nebulosity surrounding Epsilon in comparison to Bellatrix."

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