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Old 14-05-2009, 08:57 AM
vaztr (Andrew)
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M83 - gx

Maybe this should be in the BEGINNERS section - but ???

A lesson in observing!

So it's a cloud filled night and the moon's up as well, but the weather
forecast is predicting more cloud all week so it's tonight or 'never'.

I've printed off the monthly 'Skymaps.com' PDF and look for a likely
target to concentrate on tonight. I need something that's a bit
challenging but that will also AMAZE me when I see it through the new
MONSTER 8" reflector - M83 that seems to fit the bill exactly.

So a 9:00pm start - the clouds have cleared directly above me - pity
about the ones all around the horizon - reflecting all that 'lovely'
moonlight!!!

I keep remembering something about 'Dobsons Hole' but I know that my Dob elevates waay past vertical so that won't be an issue because I can cover the whole sky (fool).

So I refer to the sky chart - fortunately the number of stars shown on it
match what I can see in the sky (I should have seen this as a sign!!).
There's CRUX and if I follow 'upwards' I can get to a funny shaped square (CORVUS I find out later) then if I follow the bright stars just off this square I can see two stars (Hydra) that M83 should be equidistant from and just a little bit above. EASY!

Corvus was OK to find with the finderscope - even the two stars in Hydra I thought I'd found but I was never sure, and getting from them to anywhere else - I was just kidding myself - even with the sight scope.

OK lets try again - this time being waay more technical. I can see two
stars aligned just above the house roof that point (almost) directly at where I want to be (Menkent and another CENT star??). Surely if I just get lined up and follow that track I'll get there. (I can hear you laughing).

So I line up and am immediately successful in finding both stars in the
finderscope - this is too easy - but that's it. No M83 goes sailing by
the finderscope - try again and again and again.

Alright thats not working - what can I see - well, above the two
'pointers' I can make out a group of 4 stars, 3 in a line with one just
above - time to consult Stellarium on the Laptop and there they are hCEN 3CEN 2CEN and iCEN - so I now know that I'm 1 finderscope diameter away from M83 - WooHoo.

Now I think I've found Dobsons Hole - it has NOTHING to do with not
seeing the sky does it? - It's about not being able to move the scope in
a 'diagonal' movement, which I needed to do right now!!!!! AAAGGHH!!!!

Still, I've got this close - I can't give up yet - and miss the view of
M83 that I'll be talking to the kids about for days!!!!

So (on my hands and knees) looking through the finderscope I 'jiggle' the scope this way then that, this way then that, then OH NO! I've lost the group of four CEN stars that were keeping me on track!

So I look for something else in the finderscope that might show me where I am. Five faint stars make a 'cup' (OK cup isn't right, but I was desperate) shape. Back to Stellarium and lo and behold I've found HIP66527, HIP66469, HIP66394a and HIP66292. AND I can also see that stars HIP66563 and HIP66539 should be nearby. Back to the scope - there they are - jiggle - jiggle - jiggle and HIP66539 is centred.

I put the 25mm eyepiece in and look through it - there it is - dead centre and it's friend near the edge. Hold on! If it's friend is near the edge then M83 should be near the edge too!!

I look harder (is it possible to 'will' something to appear), nothing - jiggle jiggle and at last SOMETHING. Jiggle jiggle and the something is centred - M83 in all it's glory - which is basically a bit of a smudge that can be seen better by not looking directly at it.

I'm a bit disappointed - so reach for the 10mm ep. knowing that this baby will make M83 really POP. But to me the image gets worse - it just looks more 'washed out' - so I go back to the 25mm and gaze some more.

A 9:30 finish - back inside to my wife with very little enthusiasm.

So was it a successful night?

As far as M83 is concerned NOT REALLY - a bit of a smudge that I would miss 9 times out of 10

BUT I think I really achieved in my sky hunting - sure it took 25 minutes to find 1 thing, but I found it and I learned that 'straight up' might not be best for my scope and that persistence will get me there - even on washed out nights.

Now what should I go and look for next?

Andrew
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  #2  
Old 14-05-2009, 10:30 AM
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Terry B
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Great effort.
Now try centaurus A (NGC5128)
It wont be as high and is easier to find than M83 and is a bit brighter.
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Old 14-05-2009, 10:54 AM
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jjjnettie (Jeanette)
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M104, the Sombrero Galaxy, right near Corvus.
It's fairly easy to find too, there's so many stars pointing the way to it. Literally pointing the way.
You'll have no problems using the 10mm on this one. It's bright.
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Old 14-05-2009, 01:57 PM
beefking (Nathan)
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yeah, I learnt earlier this week how much the moon affects things. I was trying to find NGC4945 in centaurus...

I found it, but the glow from the moon, which hadn't even risen yet, had washed the sky out so much I could barely make it out.

every extended object I looked - Eta carina, Centaurus A, omega centauri - they were all washed out. still, I got to try out my new 6mm ethos on saturn, so it wasn't a total wash.
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Old 14-05-2009, 02:15 PM
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ngcles
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Hi Andrew,

Quote:
Originally Posted by vaztr View Post
So was it a successful night? ...


... BUT I think I really achieved in my sky hunting - sure it took 25 minutes to find 1 thing, but I found it and I learned that 'straight up' might not be best for my scope and that persistence will get me there - even on washed out nights. ...

... Now what should I go and look for next?

Andrew
Yes, I'd certainly call it a success.

I assume you are observing from the suburbia of Canberra, so the combination of sky-glow from suburban light-pollution and a gibbous moon is a pretty overpowering combination which will make the sky pretty bright -- far from ideal for galaxy hunting. What you likely saw was only the core/nucleus of the galaxy. The outer spiral halo is much bigger and fainter and only reveals itself well in a good dark sky.

One of the key elements in getting the best out of galaxy observing (and deep sky observing generally) is a dark sky. I'm willing to bet that in a few nights when the moon is absent, if you take your 'scope outside of Canberra's light-dome you will get a good view of M83 that will be much more impressive that what you have seen.

I've attached a .pdf of a Megastar map showing the position of M83. Please note the way the map is oriented -- west is basically up and north to the left. If you hold it in front of you facing east if should match the stars in the early evening. I reckon the best way to find M83 is to find the lowercase "y" - shaped pattern of stars formed by the 4th magnitude stars 1,2,3 & 4 Centauri (these designations are Flamsteed numbers). The top two stars in the "y" point at M83 -- as you can see from the map. This pattern of stars stands out well because they are all pretty much similar in brightness.

I've seen M83 in a 6x30mm finderscope under a dark sky -- so an 8" will show it well. Lacaille discovered it in a 1/2" 'scope around 1752. I've also seen indications of spiral structure in it with a 6" 'scope -- again under a pristine sky. A 12" will show spiral arms pretty well in a dark sky. But having said that, it's much easier to see that structure in a smaller 'scope, once you have seen it already in a larger 'scope, so don't expect it to leap out at you and hit you in the face. Learning to use a telescope is a bit like learning to play a musical instrument -- it takes time 'till you can do it really well so don't expect to be a pro overnight. Keep at it and work on you observing and finding skills and you will absolutely amaze yourself as to what you can see. Observing with a telescope is not a talent -- it is a skill that is learned.

As for what else to look for, well why not the other bright members of the M83 Cantaurus A* group ? I believe someone wrote an article on this galaxy group in the latest issue of Australian Sky & Telescope which might be helpful ...


Best,

Les D
Attached Files
File Type: pdf M83 finder.pdf (33.0 KB, 12 views)

Last edited by ngcles; 14-05-2009 at 03:21 PM.
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Old 14-05-2009, 02:42 PM
vaztr (Andrew)
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Thanx all for the replies!

I'm not sure I'll get much viewing done over the next few days - there's lots of cloud around and even talk of rain!

I'm just glad none of the kids were waiting 'all that time' to get to see a small smudge LOL

Looks like I may be off to Wylong for the June long weekend (inlaws have a HUGE farm there) - maybe that's the time for M83 and others!!!

Andrew

PS. Les - nice infomercial HAHAHA
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Old 14-05-2009, 06:13 PM
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toryglen-boy (Duncan)
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Andrew

There are many dark sky sites around, i have been to Peter Bobroffs place, and to some other places outside Canberra (dont ask me what they where called, i am not from 'round these éer parts!) but the difference it makes is quite marked. From my backyard, i dont see any fainter than around mag 4.2ish, and thats after dark adaption, at Peters place the limiting mag was around 6ish and the sky looked awesome.

If i can see M83 and M104 in an Orion ED80 visually, then when better skys are around you will have no trouble. As JJJ says, try the Sombrero, about just over a third of the way down, from Corvus to Spica, and just over a wee bit, there is litterally an arrowhead of stars pointing to it! i can see it in my ED80 (just! thanks Brian) and in my 12" i can easily see the central bulge, and dust lanes

There lots of us enthusiasts in the ACT dont think twice about sending me a PM is you want someone to bounce ideas off of, or its quite handy sometimes having a fellow observer showing you gems of the sky that you didnt know where there, and then go see them with your own scope.

an 8" dob is a great scope, and one that will serve you very well

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Old 18-05-2009, 10:11 AM
vaztr (Andrew)
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Thanx again all,

Tried M104 on Saturday night - V easy to find, esp. with the 'pointing' stars.

Again the 25mm gave a better 'overall' view than the 10mm - maybe this will change when the sky gets darker?

I was able to see the 'larger' piece of M104 (lets call it the TOP) without being able to resolve the seperation from the 'bottom'

When looking at the 'pointing' stars I was able to see all 4 bright stars making a reversed L shape plus two faint stars under this plus one other star that I can't find in Stellarium - any takers? (see attached file)

Thanx

Andrew
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Old 18-05-2009, 12:48 PM
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Jaws

Hi Andrew & All,

The star-group you have drawn is sometimes known as "jaws" because in a medium-sized 'scope it has a superficial resemblance to a shark seen side-on.

You can read more about it here:

http://www.backyard-astro.com/deepsky/top100/15.html

and here:

http://www.deep-sky.co.uk/asterisms.htm

Attached is a Megastar map with a Realsky (digitised sky survey) overlay which shows its position in relation to M104. The object you have specifically circled is a 13th mag star:

GSC 5531:1441 STAR
RA: 12h 38m 29.05s Dec: -11° 32' 53.0"
Pos err: 0.4 arcsec Mag: 13.0 / 0.3

The USNO A2 provides the fololowing catalogue data:

0750-07905586
RA 12 38 29.13 Dec -11 32 53.0
Mag 13.05

You can see a mouse-over skymap of M104 and surrounds here:

http://www.sky-map.org/?ra=12.651297...mg_source=DSS2


Hope that helps.


Best,

Les D
Attached Files
File Type: pdf 104 plus jaws.pdf (114.8 KB, 5 views)

Last edited by ngcles; 18-05-2009 at 02:32 PM.
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Old 18-05-2009, 12:57 PM
vaztr (Andrew)
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Thanx Les.

I'd checked JR's TriAtlas to Mag 12 and didn't see the star - I'd also checked Stellarium with stars to Mag 16 and didn't see it!!

I almost got excited about finding a supernova HAHA

The sky-map.org site it AWEsome!!

Thanx

Andrew
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