View Full Version here: : Observations 24/9/11 in desperandum ad astra
26-09-2011, 10:08 PM
A couple of "clear" nights recently. The first last Friday was more than a little trying due to seeing and transparency. Still, I did manage some obs. Here is the report of that adventure!
Observation notes 24/9/11
Telescope 400mm f4.9 tri-dob reflector
Eyepieces 28mm UWAN, 17,13,9 mm Naglers, Paracorr
Navigation: Night Sky Observers Guide (NSOG) and Uranometria
Seeing extremely poor due to high winds even low magnifications show stars as boiling blobs. Transparency abysmal due to smoke.
Who but a fool would observe galaxies under these circumstances?
Aquarius Dwarf Galaxy
175X Faint 5x3 haze elongated E-W with a line of 3 faint stars along the southern edge, one on the NW corner and one on the NE
NGC 7492 GC in Aquarius
175X Faint round 6 haze with 3 faint stars just resolved (possibly foreground). Foreground stars also preceding and following the GC in an otherwise sparse star field. No core and poorly concentrated.
135X Seeing very poor. A faint bluish disc.
NGC 7172/7173/7174/7176 GX in Pisces Austrinus
175X 7174 and 7176 at first appear as one 2x1 SW-NE ellipse, brighter at the NE end, but averted vision and patience reveal 2 galaxies, 7176 the brighter with stellar core and 7174 as a faint oval glow. 3 to the west is the core of 7173 which looks about 1 across and might be a elongated N-S. 7 to the NW of 7173 is 7172 which is larger and fainter 2.5x1.5, a SW-NE oval with a nucleus just discernible in a faint halo
NGC 7201/7203/7204 GX in Pisces Austrinus
175X This is a nice SSE-NNW line of 3 galaxies of similar size and magnitude. 7201 is at the southern end and looks 1.5x0.5 E-W with a bright nucleus. 8 to the north is 7203 which is a tad larger and rounder with a bright nucleus. A further 10 to the north is 7204, a fainter 2x1 E-W oval with no nucleus.
26-09-2011, 10:31 PM
Made the best of a bad situation there, good work. Was considering going out last night but was a tad windy, and for some reason my gut was telling me bad seeing. Thanks for the confirmation!
26-09-2011, 10:36 PM
Good to see you out observing, really makes me feel I need to put the effort in and at least do something in my limited courtyard space.
27-09-2011, 09:48 PM
Nice work Paddy, sometimes you just have to get out there.
27-09-2011, 09:55 PM
Too true Michael. I find it very hard to stay inside on a clear moonless night however poor the conditions might be.
28-09-2011, 07:17 AM
Nice observations in poor conditions:thumbsup:,
The Ngc 7172/72/74/76 group is a nice little gathering of galaxies.
The other group you observed sounds interesting i'll give it a go next time i'm out.
Thanks for posting
Good on you Paddy! :thumbsup:
And you still managed to bag some nice things despite the conditions.;)
See my little quote under my signature....
When you do that, then we'll start to worry :screwy: :lol:
03-10-2011, 05:51 PM
I'll let you know when that starts happening. It is good to live on the dry side of the Great Divide
04-10-2011, 02:58 PM
Very Good observation, Paddy, to disentangle the NGC 7174 plus NGC 7176 pair.
N7174 is a highly distorted object of "disky" morphology, with plenty of disturbed-looking dust, and it forms an overlap pair with the elliptical galaxy NGC 7176.
It looks like NGC 7174 is somehow stretched out, rather than being just a normal undisturbed galaxy:
(The above image is from the Atlas of Structures in Early Type Galaxies.)
Of the four galaxies in this compact group of galaxies, which is known as Hickson Compact Group 90 (= HICK 90)(= HCG 90), it seems to me that NGC 7172 is the most likely to show some kind of internal structure in visual observations, as it has an "equatorial" dust lane which is quite broad and which is noticeably distorted and/or non-planar;
The above image of NGC 7172 is a composite of two DSS images which I downloaded from the "Aladin previewer" (my favourite version of the Digitized Sky Survey).
I have in front of me a paper copy of Paul Hickson's "Atlas of Compact Groups of Galaxies", including images of all 100 compact groups; this Atlas is a nice tool for frontier-level visual observers, because the included images of the groups are not too detailed, so they do bear some relation to what can be seen visually.
P.S. NGC 7172 has a Seyfert nucleus, so you might be seeing some of the light from the Active Galactic Nucleus at the very centre of this galaxy..... but it is extremely hard to disentangle the contribution of the central active nucleus from that of the surrounding material (e.g. bulge light, central star formation, etc.)
05-10-2011, 12:30 AM
Oh, and just one more thing....
"Just for fun and profit", here is a pair of images of NGC 7172 from a paper by S. Hameed and N. Devereux :
The Left panel is optical continuum light (red light), and the Right panel is H-alpha line only.
06-10-2011, 12:15 PM
I'll try a revisit of 7172 under better conditions and see what other structure is visible. Quite a list of observing challenges that I'm putting together from your posts!
07-10-2011, 01:30 PM
N7172 is going to be a tough nut to crack, but given the amount that you do see in other objects, I think that there is a good chance that you will crack it.
You live away from the major cities, I do believe.
This must be a great blessing for a visual observer.
I always had to drive three or four hours to my observing site, and then face the prospect of being clouded out. Perhaps my large amount of time-commitment relative to my very modest actual amount of useful observing time, was why I stopped doing regular visual observing and astrophotography.....the ever-increasing masses of unanalyzed imaging data on the internet make it much more efficient for me to spend my limited free time with other people's data. In any case, I am primarily interested in the morphologies and properties of galaxies, so I will use whatever data is best for this very specialized purpose.
Best regards, robert
The "warped and bent" and/or "thickened" and/or "non-planar" dust disk in NGC 7172 is something that I must pay more attention to. I have a large "Rogues Gallery" on disk drive...which is full of many weird and wonderful Spirals and S0 Galaxies that have a wide variety of strange non-planar features (bends, twists, thickenings, tilts, etc, instead of simply the canonical "planar galaxy" that we find in the old textbooks)
07-10-2011, 08:23 PM
I do live under lovely dark skies. I have great respect for the commitment of those who pursue observing and live in cities!
08-10-2011, 10:31 PM
Currently, I probably manage about five or six visual observing sessions per year with a 12 inch Newt./Dobsonian. The interest is probably not there to pursue it very regularly, as I did for 26-27 years.
I am fortunate enough, about one month from every two, to be able to spend 5 hours every day thinking about nothing else apart from galaxies , and this has to be my focus.
The other month out of the two, I am usually studying "dirt"(invertebrates in the soil) or practicing my other scientific hobbies..... such as looking for the earliest fossil evidence of multicellular life.
11-10-2011, 06:42 AM
I'm very impressed you were able to pick up the Aquarius Dwarf in poor conditions! LEDA lists a pretty daunting surface brightness of only 16.56(B) mag per square arcmin.
I wonder if others have seen this local group dwarf and under what conditions?
11-10-2011, 10:27 PM
Thanks Steve. I was a bit surprised myself, but for once I was sure it wasn't imagination. When I cross checked with a DSS image, it all checked out. I was quite chuffed!
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