Challenge Objects - October 2005

The October 2005 DSO challenge objects were written up by Andrew Durick (astro_south), John Bambury (ausastronomer) and Mike Salway (iceman). The CDC charts were compiled by Andrew Durick (astro_south). The lunar challenge was written by Rob Mcpaul-Browne (rmcpb).

Scroll down to see each of the objects, and click on the links to download the finder chart or view the forum threads related to each object.

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Galaxy - NGC7582 + (7552, 7590 & 7599 - Grus Quartet)

Const.:

Grus

Type:

Galaxy (group)

Visual Mag.:

10.2 to 11.5

Finder Charts

RA:

23h 18.4m

DEC:

-42°22'

Wide

Diameter:

~1.2 deg

Distance:

18 Mparsecs

Zoom

Forum:

Reports, Sketches & Images

The galaxy object this month is not one galaxy, rather a grouping of galaxies (NGC 7582, 7552, 7590, and 7599) that are commonly referred to as the "Grus Quartet".  Their apparent magnitudes are (in the previous order) 10.2, 10.7, 11.5, and 11.3.  These galaxies are all of a spiral type with NGC 7552 being a barred spiral.

These 4 galaxies fit into the single low power field (@~63x) in my scope and the present an awe-inspiring view.  If your low power view doesn't allow for the fourth member to fit in, don't worry - just enjoy the three close by galaxies - still a fantastic and thought-provoking vista.  Sometimes when I'm observing I like to imagine the view of the object from a neighbouring star, or as in this case being in one of the neighbouring galaxies.  What would the view be like?  Something to ponder as you gaze at these galaxies.

The galaxies should be visible in a 4" scope from dark skies, and certainly in a 6" and upward.  After you have enjoyed the wide field view, don't fear putting some power to them to see if anymore detail can be sort.


Open Cluster - cr399 (Brocchi's Cluster)

Const.:

Vulpecula

Type:

Open Cluster / Asterism

Visual Mag.:

3.6

Finder Charts

RA:

19h 25.4m

DEC:

20°11

Wide

Diameter:

60 arcmin

Distance:

420 ly

Zoom

Forum:

Reports, Sketches & Images

Cr399 (also known as Brocchi's Cluster, or more commonly, the Coathanger Cluster) is an open cluster in the constellation Vulpecula. The cluster is spread over a 1 degree wide area of sky, and new evidence shows that this cluster might actually be an asterism. The cluster is moving towards us at a speed of 18 km/sec and 6 of the brighter stars share a common proper motion.

The common name "Coathanger Cluster" comes from its resemblance to a coathanger. Do you see this?

Because of it's 1 degree wide area, cr399 is best seen in binoculars or with the unaided eye under dark skies. The cluster is quite low in the northern sky for those in latitudes 33 degrees South or below, and the best time to observe it is early in the night before it sets.


Globular Cluster - M15 (NGC7078)

Const.:

Pegasus

Type:

Globular Cluster

Visual Mag.:

6.3

Finder Charts

RA:

21h 30m

DEC:

+12°10

Wide

Diameter:

18'

Distance:

~33,600 ly

Zoom

Forum:

Reports, Sketches & Images

M15 is also known as NGC 7078; it was discovered in 1745 by Maraldi who described it as being composed of many stars. M15 is known to extend to 18', however telescopically it only extends to about 7' or 8' in medium sized instruments.

M15 contains an exceptionally large number of stars and is one of the densest globular clusters in the Milky Way. This makes its very bright central core somewhat dominating at the eyepiece.

M15 is somewhat unusual in that it is one of only four Galactic Globular Clusters known to contain a planetary nebula, Pease 1. Pease 1 is located about 1' West of the centre of M15 and you will need good aperture of at least 15" and an OIII filter to spot it.  It is very small and stellar in appearance.  For those with the necessary equipment and inclination to chase Pease 1, here is a good finder chart and instructions.

Good luck in your hunt !!!!


Nebula - M16 (Eagle Nebula)

Const.:

Serpens

Type:

Emission Nebula

Visual Mag.:

6.4

Finder Charts

RA:

18h 18.8m

DEC:

-13°47

Wide

Diameter:

7 arcmin

Distance:

~7000 ly

Zoom

Forum:

Reports, Sketches & Images

NGC6611 is an open cluster in the constellation of Serpens, in the next spiral arm of the milkyway galaxy from us. The open cluster is a result of a massive region of  star forming gas and dust, and the Eagle Nebula (IC4703) is being lit up by these hot, young stars. New stars are still being formed in this region, near the dark "elephant trunks" seen in astrophotography of this nebula.

Original discoveries by Philippe Loys de Chéseaux in 1745-6 only catalogued the cluster, but Charles Messier noted the associated faint nebulosity in 1764.

The cluster and nebula is best seen in moderate to low powers, and under dark skies with good conditions, the faint nebulosity can start to be seen. In large apertures 12 inches and up, the dark pillars will start to be seen. A narrowband filter such as an OIII filter will help to trace some of the detail.

The nebula is an extremely popular target for astrophotographers, and the Hubble Telescope has produced some of the most amazing images of this nebula, reported to be the most popular of any HST image. The pillars make for a striking image and I'm keen to see what some of the great IIS astrophotographers can produce.

The best time to observe the nebula is late in October, but it's setting quite early in the west as we approach summer so now may be your last chance to see this great object.


Planetary Nebula - NGC7293 (Helix Nebula)

Const.:

Aquarius

Type:

Planetary Nebula

Visual Mag.:

7.3

Finder Charts

RA:

22h 29m

DEC:

-20°50.22

Wide

Diameter:

12' x 10'

Distance:

~522 ly

Zoom

Forum:

Reports, Sketches & Images

The Helix Nebula is one of the largest examples of a planetary nebula visual in amateur scopes.  While it is bright at 7.3 mag, it's light is spread over a large area and it makes the view through the eyepiece reasonably dim.

The object can be easily sighted in small binoculars and finder scopes as a ghostly blob.  The view through the eyepiece reveals the annular nature of the object, and it makes a fine photographic target.  In fact it has been the subject of some Hubble Space Telescope images that have revealed gases knots with comet-like tails at the inner edge of the annulus.

The object is best viewed at low powers (but feel free to experiment!).  There are a number of field stars involved with this object and the 13.4 mag central star should be visible in mid to large apertures using a bit of magnification. 

The brightness of the nebulosity is not even around the annulus.  It is certainly brighter in the north-east and south-west sections.  The nebula responds well to narrowband filters, in particular the OIII type.


Multiple Star - Rho Ophiucus

Const.:

Ophiucus

Type:

Multiple Star

Visual Mag.:

4.5

Finder Charts

RA:

16h 25.35m

DEC:

-23º26'10"

Wide 

Separation:

A-B = 2.9" pa 340º

Distance:

395.3 ly

Zoom

Forum:

Reports, Sketches & Images

Rho (p) Ophiuchus is also known as ADS 10049. It is an interesting multiple star system. The primary is a yellow star of magnitude 5.1, spectral type B2IV, with the secondary another yellow star of spectral type B2V at position angle 340° and quite close with a separation of only 2.9". Preceding this pair is another yellow star B 1115, which itself is a close binary, spectral type B2V. All stars appear to have a common proper motion and separation has been slowly decreasing since the first measures in 1780 indicating a related system.

Rho Ophiuchus is itself embedded in a beautiful blue reflection nebula, IC 4604. Unfortunately this reflection nebula is only visible on long exposure photographs.

Here is a link to a beautiful wide field photograph of the Rho Ophiuchus/ Antares region by Jerry Lodriguez, showing the nebulosity surrounding both stars as well as M4 and the emission nebula SH2-9.

The Hipparcos Star Catalogue Number is HIP 80473.


Lunar Challenge - Days 10 and 11

Type:

-

Lunar 100:

-

Size:

-

Best Viewed:

Days 10 and 11 of the lunar cycle

Forum:

Reports, Sketches & Images

This month we will change tack a bit and post more than one lunar feature. It is more of a Lunar theme based on Days 10 and 11 of the lunar cycle rather than a single challenge.

The features are:

  • Sirius Iridium - a large impact crater about 400km in diameter to the north of Mare Imbrium. It is edged to the north by the Jura Mountains with the south walls buried in the lava from Mare Imbrium as a result it often looks like an extension of Mare Imbrium. Best seen on day 10 and 23 of the lunar cycle.
  • Aristarchus - is a 40km diameter crater with 3000m high walls. It is the brightest crater on the Moon and can be seen by earthshine on the new moon. Best seen on day 11 and 24 of the lunar cycle but try and find it near the new moon using earthshine.
  • Kepler - is a 35km diameter crater with 2800m high walls. It has very clear ejecta rays up to 1km thick which join up with those of Copernicus. It has terraced walls with central hills and craterlets in the crater floor. Best seen on day 10 and 23 of the lunar cycle but look for the ejecta rays on day 12 or 13 when they will be clearer.
  • Gassendi - a 100km diameter crater with walls less than 2000m to the north of Mare Humorum. It has a triple central mountain 1200m high and many rilles on the crater floor. Its main feature is Gassendi A a small crater in the north wall which gives its nickname the "pearl ring crater". Best seen on day 10 and 23 of the lunar cycle.
  • Schiller - the only elongate crater on the moon is 180x70km with 4000m walls. Its formation is unknown but it was either formed from a low angle meteorite strike or the merging of two separate craters. Its floor is flat to the south and has a small central mountain to the north. Best seen on day 10 and 23 of the lunar cycle.

Try observing and either photographing or drawing these features on both nights noted and observe the differing views of the features due to the rising and setting sun shadows. An image showing the location of the features can be seen here.

We look forward to your photos or drawings, have a go!!



 

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