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Old 11-01-2009, 11:58 AM
Smirnoff
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Ic 418; Ngc 2022; Ic 2165

Seeing a rare forecast of "clear" (in those actual words, a novelty here in southern Vic), I decided to make use of it. Although there was a full moon, you got to make use of it, especially here. So, I made up a list of small, high surface brightness planetaries to observe, as these should be largely resistant to moonlight, and armed with my filters, I have the upper hand.

Charts showed an ideal setup for good seeing, but alas, southern Victoria is not known for its steady seeing. I was confronted with rubbish seeing. It was fun watching slightly out of focus stars get warped into all sorts of funky shapes!!!

Scope: 12" dob
Time: 11pm-1am
Seeing: 2/10
Transparency: 0/5 (full moon)


IC 418
Somewhat egg-shaped, uniformly bright disk at 283x. Completely disappears when you stare directly at it! Somewhere I heard that this PN responds well to the H-beta filter, so I decided to try it. With the H-beta, it was a definate improvement over the non-filtered view. None of that red that is supposedly visible at the eyepiece, although any hints of colour would've been washed out by the moon.

NGC 2022
Faint PN in northern Orion. At 176x, it appeared circular. At 283x with OIII filter, there was a hint of annularity, but the combo of moonlight and poor seeing made this hard to confirm. At this mag, signs of elongation became evident, in a NNE/SSW direction. Increasing power to 326x confirmed its annular form, but the interior was not completely dark. Its elongation was more appearent aswell.

IC 2165
Tiny, tiny PN in Canis Major, but distinctly non-stellar at 176x. It appeared somwhat pale bluish in colour. Upping mag to 353x with the OIII filter, I suspected annularity, with a hint of E-W elongation. Size is quoted as 9"x7" so it appears my suspicions of elongation are correct. Despite shoddy seeing, I decided to try what real high mags would do, so I stuck 5mm EP into the barlow for 566x (without filter). I was convinced that there was some annularity, and that this PN was also showing elongation. But it didnt appear to be an oval per se, but more of a "flying saucer" shape with a flat 'bottom' and domed 'top'. I'm suprised I got this good a view at this magnification, as when I tried to focus on some stars, all I got was a boling, mushy, quivering mess!!

At this point, the infamous southern Victorian cloud came tearing in off the icy ocean, ruining my plans for the rest of the night.

Tonight is supposed to be clear...
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  #2  
Old 11-01-2009, 01:10 PM
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ngcles
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Small Summer PNe

Hi Smirnoff & All,


Re IC 418 (Spirograph Nebula), I hadn't heard it responds well to H-Beta so I must give this a go. Im not certain, but still pretty sure the red in the rim is visible to an extent in 12". I don't have a 12" observation to back that -- just going on memory but I also seem to remember that the red rim is more evident at low-medium powers (approx x100) than high.

More/Other observations are encouraged!

My 25cm observation for IC 418 is a 1996 note that is a bit disappointing on detail:

"x181 17' TF. Mag 9.3 Size 12". Quite small but a lovely object, quite exquisite. Very hard edges, brightens smoothly to the centre where there is embedded a mag 11.5 central *."

But I seem to remember the effect of it "disappearing" too. From memory (unfiltered), if you stare at the central star (ie direct vision), the disc disappears. NGC 3132 on the Vela/Antlia border in an 8" does a similar trick.

My 2006 46cm observation is a bit more detailed and on a very good night at Bargo when the seeing was somewhat better than average:

x85, x185, x317, x371 x634 (Unfiltered, UHC & OIII)


IC 418 Planetary Nebula *
RA: 05h 27m 28.2s Dec: -12 41' 49"
Mag: 10.7 (P) Size: 12.0" Class: 4
Mag C. Star: 10.1 R.V.: ---

This is an easy find about 5 degrees SE of Rigel. At lower magnifications, this PNe shows something visually that is near unique in the sky -- unfiltered, the edges of the halo are a dull crimson red, while the inner halo is bright blue. Overall it is very small, about 15" diameter but at higher magnifications (x371 & above) seen to be very slightly off-round in PA 30. The disc is bright blue with a very bright rim and a very bright bluish central star. There seems to be a slight dimming just outside and around the central star. Overall has very high surface brightness. Best at x 317 and x371.

The "spirograph" type detail didn't show up though!

Re NGC 2022, this is a quite nice PNe and my own impressions are similar to yours. In 1996 with 25cm under a suburban sky this is the note:

"x181 17' TF x276 11' TF. Mag 11.9 Size 25". Sparse field. Small, 25" diameter, slightly elong in PA??, grey annulus in form with a central hole which is not quite dark and seems about 10" diameter. Looks like a donught.

And with 46cm in 2006:

x185, x317, x371, (Unfiltered, UHC & OIII)


NGC 2022 Planetary Nebula *
RA: 05h 42m 06.2s Dec: +09 05' 13"
Mag: 12.4 (P) Size: 35.0" Class: 4+2
Mag C. Star: 15.8 R.V.: ---

At x185 this PNe seems round but is shown to be oval at x317 and x371, about 30" x 25" in PA 0. It has a well defined rim that is slightly brighter than the balance of the halo and it dims slowly to centre making it seem weakly annular. There is some ill-defined faint fuzz outside this rim that adds little to the overall size. Responds strongly to OIII. Weakly bluish unfiltered. No central star visible though at mag 15.8 it does not seem out of the question, but it wasn't there to be seen.

So there you go.

Another good report mate and thanks for letting us all know you impressions of these nice PNe.

Smirnoff wrote:

"Tonight is supposed to be clear... "


Of course, its Full Moon -- isn't that always the way!


Best

Les D
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Old 11-01-2009, 04:53 PM
Rob_K
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Nice report again Smirnie! Intelligent choice of targets to suit the moonlit conditions, well done! Loved the descriptions...

Cheers -
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Old 12-01-2009, 09:37 PM
Smirnoff
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Thanks Les and Rob!

Les, it seems that IC 418 doies respond quite well to H-beta, because using this filter, the nebula wasnt dimmed at all, infact the filter seemed to improve upon the non-filtered view. ANd thankyou for your own accounts, I enjoy reading these as it helps with my own obervations! You say that the central star of NGC 2022 is mag 15.8, I've seen mag 15.95 stars with my 12", however I doubt I'll catch the central star in NGC 2022, as my obs of such extremely faint stars have been done under exceptional winter transparency, while hunting galaxies in areas such as Pavo and Phoenix (i.e. almost directly overhead!!)

Cheers and clear skies!
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Old 12-01-2009, 09:55 PM
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ngcles
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Hi Smirnoff & All,

Quote:
Originally Posted by Smirnoff View Post
You say that the central star of NGC 2022 is mag 15.8, I've seen mag 15.95 stars with my 12", however I doubt I'll catch the central star in NGC 2022, as my obs of such extremely faint stars have been done under exceptional winter transparency, while hunting galaxies in areas such as Pavo and Phoenix (i.e. almost directly overhead!!)
Well there's that and the fact that the PNn (central star) is sitting within a (relatively) "bright" spot -- the PNe halo itself that makes it harder to see the faint star, rather than in native "uncluttered" sky.

Still, the halo of NGC 2022 is not overly bright so I thought 15.8 was do-able in the 18". Can't discount the possibility of seeing it in 12 but much, much harder in that aperture I'd think.

You'd need quite dark sky and very good seeing and fairly high magnification at least to succeed and the concurrence of dark sky, and very good transparancy and good seeing is not all that common -- particularly at Vostok!

Best,


Les D

Last edited by ngcles; 12-01-2009 at 11:55 PM.
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Old 12-01-2009, 11:45 PM
Smirnoff
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Quote:
Originally Posted by ngcles View Post
Hi Smirnoff & All,



Well there's that and the fact that the PNn (central star) is sitting within a (relatively) "bright" spot -- the PNe halo itself that makes it harder to see the faint star, ratherr than in native "uncluttered" sky.
that's true, probably not much chance really until one makes it to the big leagues

Quote:
Still, the halo of NGC 2022 is not overly bright so I thought 15.8 was do-able in the 18". Can't discount the possibility of seeing it in 12 but much, much harder in that aperture I'd think.
I doubt it would be possible in a 12", unless one was observing from pristine skies. IMO it should be within reach of an 18" under excellent conditions. I've noted that these mag 15.9 stars in near perfect transparency, from my outer suburban location, nearly overhead, are that they are very feeble, just barely visible with averted vision, and only held in sight intermittently. The added complications of nebulosity and lower altitude would almost certainly be the nail in the coffin for this aperture class.

Quote:
You'd need quite dark sky and very good seeing and fairly high magnification at least to succeed and the concurrence of dark sky, and very good transparancy and good seeing is not all that common -- particularly at Vostok!

Best,


Les D
That's for sure! Down here at Vostok (better known as Melbourne), seeing has been garbage every night I've been out since last summer. My last nights of good seeing were last January and February! Realistically, I'm limited to 200x at best with my scopes, although pushing 300s and even 400s doesn't seem to bother these PNe's much despite the poor seeing. Stars however ,unfocusable at anything beyond 200x.

I did get a fantastic view of the the 6 trapezium components at sub 200x mags.
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