sponsored by psychohistorian.org

DOCdb

Deep Sky Observer's Companion – the online database

 

Welcome, guest!

If you've already registered, please log in,

or register an observer profile for added functionality.

List:

log in to manage your observing lists

 browse:

 

 position:

 

 next:

 

 options:

summary

rename

prune

trim

remove

close

copy

combine

plan

bookmark

load

new

delete

marathon

favourite!

Full database:

Entire DOCdb database of 18,816 objects.

 browse:

 position:

NGC 6445 (14,720 of 18,816)

 next:

oc gc pln bn dn gx gxcl ast aka lost

Object:

list

bookmark

finder chart

altitude today

altitude (year)

 search:

½°, , in DOCdb


Warning: date(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone. in /home/yivumoo/public_html/show_object.php on line 167

show browsing

Crescent Nebula

NGC 6445, ESO 589-9, HD 161944, Hen 2-290, PK 008+03 1, PN G008.0+03.9, PN Sa 2-248, Little Gem, Bennett 98b, Crescent Nebula, II 586, h 1986, GC 4333

RA: 17h 49m 15.21s
Dec: −20° 00′ 34.5″

Con: Sagittarius
Ch: MSA:1369, U2:338, SA:22

Ref: SIMBAD

(reference key)

Type: planetary nebula

Mag: B=18.9, V=?

Size: ?
PA: ?

Image gallery

Photos  (1)

Select a photo and click the button to view

Historical observations

William Herschel (c.1784)

Synonyms: H II-586

Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "pB, S, iF."

Published comments

Helwan Obs. Bulletin No 22 (1921)

! Planetary, 40'', trapezium-shaped object with very sharp corners; the two parallel sides are considerably brighter than the other pair, and lie in PA 60deg and 240deg; the n.f. corner is a right angle; no indication of a central star.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 13.0 mag planetary nebula.

Photo index

Photo Index by Jim Lucyk: Sky&Tel. 8/84 p187, Deep Sky #3 Su83 p10, Deep Sky #15 Su86 p8, Deep Sky #20 Fa87 p10.

Modern observations

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "11.8M (listed as 13M in BCH and others; looks much brighter!) 35" diameter; soft, round blob; N-filter and >200x show oval ring with bright knot in NW sector; 13M star 40" to NW; GLOB N6440 is 20' S and a little W."

Ware, Donald J

Donald J. Ware:"This planetary nebula is rather large, about 50" in diameter. It is grey, and averted vision hints at a darker region near its center, implying annularity. There is a field star very close to, but not imbedded in the northwest side of the nebula."

Steve Coe

Steve Coe, observing with a 13" f/5.6, notes: "Pretty bright, large and has a elongated box shape at 200X. The outer rim of this planetary is brighter than the center. A white and blue double star is nearby. It shows a small dark lane at high power and is definately not a 13th mag object as listed, I estimate 12."

Steve Coe: [amastro] Summer Planetaries

Howdy all;

Well, the clouds went away for a while and I got out to do some real observing. What a nice break! Here are some of the notes of a few summer planetaries that I observed. For those of you still clouded out, have faith, for I have seen the Milky Way and it still exists, honest.

Steve Coe

NGC 6445 in Sagittarius Eagle Eye site S=7 T=7 13" 150X--pretty bright, pretty large, not brighter in the middle, elongated 1.8 X 1 in PA 165. There is a nice, easy to split, white and blue double star to the east of this planetary nebula. Ken Reeve's 20" f/5 light green in color, a bizarre shape, two rounded squares of nebulosity with a dark lane in the middle. The outer rim of the nebula is brigher than anything inside it. With averted vision a very faint loop of nebulosity extends away from the bright section toward the south. A unique object.

(unknown)

(PK8+3.1) Mag=11.2. Sagittarius: 17h, 49.2m; -20° 1' ("Little Gem"?) At first we were perplexed by Ferguson's article, for he describes this fairly large (3' circular) planetary without a nickname in his list; yet he ascribes the name "Little Gem" to NGC-6818, also in Sagittarius. However, practically every other reference consulted calls NGC-6445 the "Little Gem" nebula. Turning to Dr. Marling for clarification, we were informed that 6445 was discovered in 1882 (attributed to Pickering, probably reported by E. C. Pickering to Dreyer, but not necessarily first observed by E. C. P. as we found out years before, when researching the Horsehead nebula) and that it is -- re Sinnott's NGC 2000.0 -- known as "Little Gem". All other references that stem from this volume also concur.

After passing from that issue to the more personally- relevant one of its visibility in our telescope, we determined that NGC- 6445 is rather hard to find in the fall, with Sagittarius irrevocably sinking further below the western horizon, but that it could be detected with some diligent searching. Even in the rough seeing just 20 degrees above the skyline, this small speck of bright light stood out from the sharper stellar points in a crowded, milky field. We identified it positively, using a general narrowband nebular filter at 80x: with Lumicon's O-III filter, at 200x the nebula was bright, while the surrounding stars almost disappeared. Under these poor sky conditions, it appeared to be a bland, uniform disk.

Sutherland Astron. Soc. (NSW, Australia)

In the online Southern Observer (article "The planetary nebulae of Sagittarius") this planetary is recorded as: "Directions to this object are a little difficult but here goes: locate G Scorpi in the tail of Scorpius near M7. Lock the RA axis and slew 17 degrees N and there it is in the same low power field as (22' N of) NGC 6440 a mag 9 globular cluster, M23 a brilliant open cluster is 2 low power fields away ENE. The planetary is sizable at 1'x30" in 25cm with a dumbbell shape a little reminiscent of M27. At Mag 11.2 it could hardly be called bright. The central star at mag 18.9 might just be visible given a 30" 'scope. RA 17.49 Dec -20.0. Winter."

Contemporary observations

Magda Streicher

1997 August 05

Location: Pietersburg South 23 53. East 29 28.

Sky conditions: Fair.

Instrument: Meade 12 inch.( Eyepiece super 40mm).

Date: 1997 August 05

Field of view: 52.7 minutes.

This planetary nebula had an elongated shape; no sharp edges and shows an open area towards the middle. Fairly bright with an uneven disk and a greyish colour.

(no date)

12-inch f/10 SCT (EP: 2-inch 32mm SW 95x 42' fov; 2-inch 14mm UW 218x 23' fov; 2-inch 8.8mm UW 346x 15' fov)

This planetary nebula has an elongated shape, no sharp edges and shows an open area towards the middle. Fairly bright with a slightly grey colour. Very faint star more or less 12th magnitude situated on the north edge, and somehow the planetary appears rounded in that area, in contrast with the south edge where the nebulosity seems to be cut off. A 7th magnitude whitish star can be seen just 4'.5 arc minutes to the east.

Richard Ford

2012 September, 14th

Location:Night Sky Caravan Park,Bonnievale.

Sky Conditions:Whole Milky is visible.The sky is clean.

Atmosphere stable with little interference.

Instrument:12-inch Dobsonian.

This planetary nebula is seen as an oval faint glow of light and that this nebula is somewhat elongated and well defined.At 167* and 214*with my OIII filter this planetary nebula's oval like shape with its pale green colour is seen. This planetary nebula measures 5.2'*2.6'Chart:No.315,NSOG Vol.2.

Favourite lists

Lacaille's catalogue

The Messier objects

Dunlop's catalogue

The Bennett objects

The Caldwell list

Named DSOs

Object search

First search phrase

    and

Second search phrase

Type of object to include:

open cluster
globular cluster
planetary nebula
bright nebula
dark nebula
galaxy
galaxy cluster
asterism & stars
unverified/lost
nova

The Bug Report

DOCdb is still in beta-release.

Known issues, feature requests, and updates on bug fixes, are here:

> Bug Report

Feedback

Found a bug? Have a comment or suggestion to improve DOCdb? Please let us know!

> Contact us

Help!

DOCdb is a free online resource that exists to promote deep sky observing.

You could help by sharing your observations, writing an article, digitizing and proof-reading historical material, and more.

> Find out more

Everything on DOCdb.net is © 2004-2010 by Auke Slotegraaf, unless stated otherwise or if you can prove you have divine permission to use it. Before using material published here, please consult the Creative Commons Attribution-Non-Commercial-Share Alike 2.5 License. Some material on DOCdb is copyright the individual authors. If in doubt, don't reproduce. And that goes for having children, too. Please note that the recommended browser for DOCdb is Firefox 3.x. You may also get good results with K-Meleon. Good luck if you're using IE. A successful experience with other browsers, including Opera and Safari, may vary.