Having just recently acquired a 200mm reflector (still playing with the concept of collimation given my refractor background) I found myself viewing a number of objects in greater detail than I had in a long time. Given the time of year naturally gravitate towards Eta Carina which left me with the following question to visual observers:
How visible is the Homunculus?
and the related question:
What might be the expected minimum required to view?
(for example it is often indicated that at least a 200mm is needed for the horse-head, coupled with dark skies)
I have endeavored to find out how big it is from web searches and the like but no clear estimate (I did find a statement to the effect it was about 16 arc-seconds).
Thanks for any insights from your collective wisdom.
Regards
Last edited by Coen; 23-04-2010 at 01:07 PM.
Reason: formating
have a look at the thread I started on Eta Carina the other day. RobH has included an amazing link detailing landmarks of this amazing nebula, including the Homunculus. Have a look at the link he provided. I've since added my observations of the nebula and the Homunculus.
Requirement wise to see the Homunculus, anything over 100X will show it clearly. I saw it, no problem at 133X. It is a little smaller than Saturn through a scope, and it is a bright orange in colour. A nebula filter will actually cut its light out. Even thought the moon is out this evening, the Homunculus is bright enough to see it clearly despite the Moon glow.
Used a 300mm dob from BinTel that was required to be very nicely collimated to see the very small features of Eta Car and Humonculus nebula.
(Have not published this OR as it would be 3 pages on IceInSpace and I think that is beyond what the Forum would like to see as a post so I am going to not post my last 2 nights that are long ORs)
Here is my best observation from March new moon and since it is so tiny you will need very very good seeing but I bet you don't need exceptionally dark skies as it is fairly bright. Saw both lobes but I was in rather dark sky. I neglected to record the directions of things then wrote this after 4 weeks so sadly I may have some directions wrong if from memory but the info was from my tape made when I was observing.
con: Car cmt1: EtaCarAndHomunculusNebula: fav: F5 tape: 1:04:00
GSC 8626:2809 8626:2809:1 PPM 339408 SAO 238429 HD 93308
Star 6.10 0.0.603 --- TYC 10 45 03.5 -59 41 04
2:05am 5mmNag 305x What is striking at first glance is this area has a distinct yellow-orange sort of color, especially close in to Eta Car itself. Star itself sits within a small dark disk before main brightness starts in. The two lobes look as if a big peanut with the bottom one [more East?] being a brighter lobe. The trailing lobe is more difficult to see and may be smaller. The edge of the peanut on the brighter lobe is fairly sharp in cutoff of the light. In the brighter lobe I detect from time to time 1 or maybe 2 different darker spots along the main axis of the peanut but they are only mildly sharp in moments of good seeing. There are two stars on the other side of the dark disk that are tiny points of similar mag that when taken in with the Homunculus Nebula as a whole add a nice touch to this tiny but unusual field. I detect from time to time a small spike comming off perpendicular to the peanut. [This object requires EXTREMELY accurate collimation and this I learned after 2 earlier attempts]
When I had my 10", I could clearly see the striations across both orbs of the Homunculous.
I don't see why you shouldn't be able to see the same.
The Horse Head though.....save your sanity and image it instead.
Hi Coen, the Homunculus itself is very bright and quite pronounced as two lobes protruding in opposite direction from Eta and you should be able to spot 'something' around Eta in pretty much the smallest scope. However to see clear details in the lobes a large scope is preferable, I would guess 200mm+.
16 arcseconds sounds about right. I took an image of it last year with quite a lot of detail, see thread here: http://www.iceinspace.com.au/forum/s...ad.php?t=56087
I'm using a 250mm Newtonian.
Hi, my primary scope is a Meade 8" LB and from a dark site you will see lots. It always reminds me of a slice of apple pie. Triangular, nicely flaked crust and a wee bit of brown sugar sparkling on the top.
Brian
Hmmmm, not to hi jack the thread but after looking at the photos and reading the descriptions it seems I may be mistaking the pie slice for the Homunculus?
Brian
To get the best out of observing the homonculus visually you need good seeing and high power. An 8" scope is plenty, to see good detail but you need 240X as an absolute minimum to get detail in the lobes. A 10" scope is better again and anything over 15" gives you an enormous advantage. Andrew Murrell and I often observe this target in our 18" and 25" scopes at 600X plus. I have on one occasion observed it at 1050X in my 18" scope under exceptional seeing. It is one target which holds up exceptionally well under very high magnification, but you need decent seeing.
The structure of the lobes has changed fairly noticeably over the past 4 or 5 years. The dark internal blotches have grown and the dimmer lobe has dimmed in comparison to the brighter one.
Having trouble locating the STAR itself in Stelluriam. Could someone please give me the catalog number that pin points the start rather than the nebula.
Edit...I take it as mentioned its "HD 93308" but when I zoom in with steluriam its not highlighted and drifts quickly as all objects do on close zoom. It's just anoying that such an important and popular star is not highlighted with its name.
Just to be sure and because I don't mind admitting I often get confused...is this the "Eta Carina" Star?
To get the best out of observing the homonculus visually you need good seeing and high power. An 8" scope is plenty, to see good detail but you need 240X as an absolute minimum to get detail in the lobes. A 10" scope is better again and anything over 15" gives you an enormous advantage. Andrew Murrell and I often observe this target in our 18" and 25" scopes at 600X plus. I have on one occasion observed it at 1050X in my 18" scope under exceptional seeing. It is one target which holds up exceptionally well under very high magnification, but you need decent seeing.
The structure of the lobes has changed fairly noticeably over the past 4 or 5 years. The dark internal blotches have grown and the dimmer lobe has dimmed in comparison to the brighter one.
Spot-on advice John -- couldn't have said it better. Seeing is very important if not critical to seeing detail because it is very small and needs quite a bit of magnification to enlarge it to the point where detail can be more easily seen. In my 18" x247 gives a good view if the seeing is cooperative, better at x317, x464 and x634, but (the last two) only if the atmosphere is truly on-song (rare).
Also, the central star is now much brighter compared to be small nebula surrounding it than it was say 10 years ago (in the pic at the attached link). I can can only vaguely make out the outer dark red halo in the very best conditions (this may be dependant on how red-sensitive your eyes are).
As John has correctly said, quite a bit of change (in context) has occurred in the last half-dozen years with the dimmer lobe now a lot dimmer than the bright one, the "bites" out of the side of it making that dimmer lobe look somewhat "anchor-shaped" and the dark blobs in the bright lobe growing in darkness, size and number. Without doubt one of the best small objects in the whole sky -- very, very tasty!
Its dead easy to find. The star is the brightest one and its in the brightest part of the nebula, its just that the homunculus neb itself isn't obvious until you pop in a high power eyepiece.
