Eta Carina

[barx1963]

Just got back in after a nice couple of hours observing B4 the moon came up. Highlight was trying out my Xmas pressy (TV barlow) on my 13mm Nagler on Eta Car. Not just glimpsing the Homonculus but seeing the 2 lobes clear as day with an actual 3d look to them. Seeing structure with one lobe clearly pointing towards us slightly with the other pointing away. Absolutely brilliant!
Nailed a few other obs as well. Will post a full report tomorrow, unless it is clear of course!!!

[mozzie]

nice to have some clear weather malcolm i had a nice look around lmc before the moon rose theres some nice b/n and o/c in there you always seem to find something new all the time

[richardda1st]

After reading your brief report on Eta Car I decided to have a go at it my self as I haven't as yet. Beautiful clear sky all afternoon and late evening, so I set up my scope nice and early for a midnight view. Read up some facts on Eta Car, interesting stuff. Then around midnight I went out all apprehensive as to what I will be able to view, looked up and you guessed it, solid cloud cover.:mad2:
I suppose at Colac you'd have very dark skies.
I'll try again tonight.

[barx1963]

Hey Richard. Colac does have dark skies but where I am there is still a lot of glow from industrial area and the highway just south of me. Keep persevering, the actual homonculous is not easy to see as it is faint in comparison to the rest of the nebula.

Malcolm

[richardda1st]

Hi Malcolm, just took the scope out to let it climatise, pefectly clear sky again so far. I think I'll keep a closer look at the sky and maybe start earlier tonight, but hope for clear skies around 1am and later. This will put Eta Car nice and high.:thumbsup:

[ausastronomer]

Hi Malcolm,

You need to use more power on the homonculus. On nights of good seeing it is not uncommon for me to observe it at 500X plus and on rarer occasions at 700X to 800X. The view will hold up better at high magnifications than planetary views in variable seeing conditions.

At high power in a decent aperture scope it is fairly easy to see detail within both lobes of the nebula. Both lobes actually have holes in them and their structure has changed fairly significantly in the past 2 or 3 years.

Cheers,
John B

[barx1963]

Richard - keeping fingers crossed!
John - thanks for that. Haven't tried it beyond about 230x, which is as much as I can get with decent EPs in my set, the short Plossls are next to useless IMHO. Anyway, hope to get a better look at it once I have some better EPs!

[richardda1st]

Had a good session last night concentrating on Eta car. No clouds but forget about the moon coming up behind me. No real detail in the nebula but not to sure as to what to concentrate on. Can you tell me if Eta Car is the relatively brighter yellow star in the nebula to the left of a formation of stars forming a w (as per the image taken by Martin of this nebula).
http://www.iceinspace.com.au/forum/attachment.php?attachmentid=69500&stc=1&thumb=1&d=1262558546

Moved on to the Tarantula for a while, was seeing some good detail. Seems to get better as I get familiar with the structure of the target.:)

Thanks Martin for your image of Eta Car, hope you don't mind me referring to it as it clearly shows most of the stars in the nebula.:D

[ngcles]

Hi John,



I'm glad you said that John about there being change particularly over the last few years. I look forward every jear in Dec/Jan to getting a look to see what has happened over the last few months it has been scraping along the southern horizon. Personally I like the view at x371 best when the seeing is up to it -- and it rarely is where I observe.

The lobe pointing obliquely away from us has about halved in brightness over the last few years and it's holes on the side (cutaway's at the sides making the bottom lobe look anchor-shaped) appear to have become bigger and darker. The brighter lobe is becoming more knotty and the central region (the "waist" between the lobes) is brighter as is the central star.

IAU circular 9103 issued on 1 January 2010 includes some very accurate photometry performed at Perth Observatory by David Frew and others that puts the magnitude of the central star (Eta itself) plus the Homunculus surrounding it at 4.65 in mid-November. I estimated it visually on 13th December 2009 at between 4.35 and 4.45 (the lower being the more likely). It had been estimated visually in early October 2009 at about 4.1. There were several visual extimates around the 4.5-4.6 mark in October-Nov. It just doesn't seem that long ago it was about mag 6.5-7.0 -- guess I'm showing my age!

This increase and variability in visual brightness is not necessarily evidence that "she's about to blow" but more likely that Eta is finally starting to clear the Homunculus away and shine out of it -- rather than through it.

It would appear therefore that as the material is being cleared out, there is less infrared and more of the visual and shorter wavelengths getting out. Change is occurring very quickly (on astronomical time-scales) and it is always interesting to watch.

And yes Richard, it is that yellowish star -- you need to use more magnification to see it's true nature. One of the most wonderful objects in the sky!!

More general info: http://etacar.umn.edu/etainfo/history/


Best,

Les D

[pgc hunter]

My best views of the Homunculus come at 200-300x. Anything above 400x just results in a crappy blur....I believe this is because the Homunculus is a very "high frequency" object, i.e. it contains lots of fine detail which to the best of my knowledge doesnt exist in any other nebula in the sky, and thus the slightest disturbance of seeing will wipe it out.

[richardda1st]

And yes Richard, it is that yellowish star -- you need to use more magnification to see it's true nature. One of the most wonderful objects in the sky!!

More general info: http://etacar.umn.edu/etainfo/history/


Best,

Les D[/QUOTE]


Thanks Les, I have scanned a few of those site, will do some more in greater detail as I get more familiar with Eta Car. I was using TV32mm & 11mm Plossls with a 2.5x powermate in a 250mm f5 newt (288x max). The views were clear, just need to do some more viewing to start recognising the features that are probably staring me right in the face. Will try with more magnification in my next attempt.:thumbsup:

Cheers
Richard

[barx1963]

Thanks for the detailed info Les, a mine of information as usual!
This is very interesting as when I was observing Eta Car the other night I thought to myself "You know.I reckon thats brighter than last year" Last time I saw it was probably around June I think, and I cannot remember being able to find it so easily, in fact I was a little frustrated on a couple of nights when it was hard to find. Now you look and there it is. Might just be my observing skills are getting better;);) or the seeing was not very good last year, and the last week down here has been magnificent!

[ngcles]

Hi All,

Tonight was the first clear night in a week-odd and luckily we had excellent conditions for the open-night to commemorate the 400th anniversary of the discovery of Jupiter's moons at Sydney Observatory.

After it was all over and was almost home (about an hour's drive) I stopped at a park just down the road from where I live and spent about 5 minutes making a quick naked-eye estimate of Eta Car (as you do ...). Using SAO 238343 (Mag 5.08) and SAO 251090 (Mag 4.56) which are very handy orange stars each about a degree from Eta Carinae, I thought it virtually the same as the latter placing it at about 4.5 - 4.6.

More interesting stuff here:

http://www.iop.org/EJ/article/1538-3881/118/4/1777/990278.text.html

and here:

http://www.universetoday.com/2009/11/25/eta-carinae-a-naked-eye-enigma/

quite technical but fascinating: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2005MNRAS.357..895F& data_type=PDF_HIGH&whole_paper=YES& type=PRINTER&filetype=.pdf

and here: http://www.etacarinae.iag.usp.br/

and some general stuff about the most massive Milky Way stars (inc Eta) is here:http://www.tim-thompson.com/bright-stars.html


Best,

Les D