object selection process for august obs. chlge.

[mental4astro]

Hi all,

Thought I'd get the ball rolling on nominations for August's Obs. Challenge.

I'm putting up a selection of objects hopefully to span a wide range of experience and scope sizes, even a couple of naked eye features.

Naked eye:

Scorpio Constellation: rather obvious for most, but if you haven't seen it before you won't forget it. At this time of the year it is directly overhead in the early evening. Its most distinctive star is its brilliant red heart, Antares.

Sagittarius Star Cloud, in Sagittarius. It is the densest star cloud of the entire Milky Way. You could be able to see this feature of the Milky Way from light polluted areas if you are able to shield out surrounding street lights. It lies in the direction of the centre of our Milky Way galaxy, it is actually located in the nearby spiral arm between us and the galactic nucleus. The Milky Way's centre lies some 30,000 light years in that direction. The star cloud is located just of the 'sting' of Scorpio, and right next to the M8/M20 complex. The big open star cluster M7 lies between this star cloud and Scorpio's sting.

Easier targets:

M22, in Sagittarius. This globular cluster is one of the gems of the sky. It starts to resolve in smaller scopes. Interstellar dust occults its lluminosity by some 2 magnitudes!

NGC 6752, in Pavo. Another big globular gem that begins to resolve in 3" scopes.

More Challenging:

NGC 6744, in Pavo. A large face on barred type galaxy. Though large it has a low surface brightness. HII regions (nebulous star forming areas) & OB star associations (son-of-a-gun big stars) in its arms begin to become defined in scopes from 10" up. Its low surface brightness can make it tricky to find in a scope, yet binocuars will show it a little more easily from a dark site.

NGC 2573, in Octans. A revisit from an earlier challenge, but its unique position in the sky I think makes it worth while for its nomination. This faint galaxy is very, very near to the South Celestial Pole, meaning it is visible year round from southern latitudes. I wasn't able to nail it in its last Challenge appearance, & I'm making it a priority for my observation program for this month. A really difficult bugger too.

Any suggestions for some doubles or varible stars?

And a couple more offerings: NGC 7009 (Saturn nebula) & NGC 7293 (Helix nebula) two distinct planetary nebulae, NGC 7552/7582/7599 galaxy complex.

[Rex]

Hi Alexander,
Nice choice of objects, hopefully will get a chance to have a look at them. You also mentioned the magic words. Double stars are one of my favourite types of objects, especially when the moon is around. I have made up some dble star charts over the years for some of the constellations (will eventually be a set for each, but it takes time to accumulate these thigs). I have attached one of my newest sets. This set is for Triangulum Australe. I haven't had a chance to confirm these yet so there may be mistakes. When I read your comment I thought it may be appreciated by the group. I also usually include dbles ranging from very close to very wide, so should be some for everyone to try. Enjoy. Thanks.

[Paddy]

What about NGC 6876 galaxy group in Pavo and whilst in Grus, planetary nebula IC 5148 in Grus?

[mental4astro]

Rex, I've had trouble opening your file. Any chance you could suggest and detail some doubles?

Paddy, your nomination has got me started on a new quest for interacting galaxies. You JUST HAD to get me going!

I've got one more nomination to add, it being both naked eye and a telescopic target, and lasting for a brief period of time. At the moment there is a conjunction of three planets occuring in the western sky during the early evening- Venus, Mars & Saturn. Venus is unmistakeable just after sunset, the brightest 'star' in the sky. Just above it are two smaller 'stars'. The one on top of the trio is red in colour- Mars. The other 'star' then being Saturn.

Telescopically Mars is not much of a show. It is receeding behind the sun as Earth has overtaken it in its orbit. Also being small in size, you'd be lucky to make out any type of planetary disk. Saturn, while too receeding, because it is much larger physically, its rings and disk are still resolveable. You may even see the shadow of the rings cast onto the planet. Harder to spot is the shadow of the planet's disk cast onto the rings behind it. Details within the rings is impossible as they are still too shallow in angle. They are slowly widening after last year being edge-on and invisible to us. They will continue to widen for the next 6 years before starting to close again.

Any further nominations before this month's Challenge is formalised?

[Rob_K]

I suggest the Rain Galaxy and the Cloud Nebula... :(

Cheers -

[pgc hunter]

May I suggest the Sun, it is a real challenge from this perpetually cloudy and rainy abyss.

[Rex]

[QUOTE=mental4astro;621599]Rex, I've had trouble opening your file. Any chance you could suggest and detail some doubles?

QUOTE]

Hi Alexander, Sorry I missed this mate. I have responded in the other thread and attached the pdf's seperately. Thanks.