Object of the Week December 23, 2012 - IC418 The Spirograph Nebula

[Dragan]

IC 418 (The Spirograph Nebula)

Planetary Nebula in Lepus the Hare

05 27 28.2
-12 41 49

Mag: 9.7
CS: 10.1

IC 418 is unique in that its one of the few objects in the night sky that can exhibit some distinct colors other than the drab grays and greens we're accustomed too. This is one object that consistently seems to display the most color to the most amount of observers. Disclaimer: Color perception in an object is obviously a subjective matter and its an attribute that is hard to quantify objectively. Your results may vary. (this OOTW has got me to thinking and I'll post a new thread shortly to get us all talking about color in an EP)

Located south of Orion near the northern border of Lepus, IC 418 is 12" across and somewhat comparable in size & brightness to NGC6543 in Draco or NGC6826 in Cygnus. Scopes as small as 4" should pick out IC418 though you'll probably need something larger to make out the color. I've never purposely looked for color in IC418 in anything smaller than a 16", but even in the 16" I was able to make out a ring of color along its circumference.

In my 25" and other larger scopes the true colors of this object come alive. I'm able to see a pink/magenta color along the circumference with a what appears to be a white core. Its this contrast between the core and edge that simply amazes me. No other object I know of has this stark contrast of colors. Simply beautiful!

Now, in the 48" the view becomes unreal. (Is it just me or am I really starting to see a connection between really big glass and incredible, knock your socks off views :thinking:) The first time I observed IC418 in the 48" was on the 23rd of February 2009.

At 375x & 488x, faded mottling was visible throughout the core as was the CS. The core is visibly white with the PN exhibiting a bright pink circumference. Pink! Pink! Pink! Wow!.

410
(Hubble Heritage-APOD)


411
Here's an image that gives kind of a representation I see in the EP. The core I see isn't quite as large or bright as it is in this image, but the color contrasts are somewhat accurate for me. (Unfortunately I couldn't find a credit for it.)

One last thing. In the above image, you can see what appears to be an extended halo. This isn't anything I've ever observed visually before nor have I ever heard of anyone else seeing it. (I've never known about this until now) I did find this paper (http://arxiv.org/abs/1204.5816) on the subject confirming an extended halo around IC418 in the IR. Is this the same halo that's described in the paper? Is it at all visually observable?

And of course,

"GIVE IT A GO AND LET US KNOW"

GOOD LUCK AND GREAT VIEWING!

[Jimi Lowrey]

That halo around IC 418 looks interesting. I did not know that it was there. I am going to try for it with low power and the NPB filter next time I am out. I'll report back if I have any luck with the faint halo.

[Paul Alsing]

Hi Jimi,

An alternate name for this guy is the Raspberry Nebula, and it is easy to see why. According to Kent Wallace, this is only 1 of 3 DSO's in the entire sky that can distinctly be seen as red, although I have seen it mostly as pink.

This is another object that I viewed through the 82" up the road from you, and my experience was different than any of the other observers there that night. Here is what I wrote at the time;

"IC 418; This smallish PNe is said to have a red rim. When I first put eye to eyepiece this red rim was obvious, but after just a few seconds the red almost completely disappeared! If I closed my eye for several seconds, it came back for a moment or 2. Anyone have an explanation? Otherwise, this is a bright planetary with a bright CS. The interior was not exactly smooth, but not exactly detailed, either, very hard to describe. I guess that the word "mottled" works here. It seemed to me to have an overall color, but it was difficult to tell exactly what that color was... hmmm... a very curious object."

[Dragan]

Paul,

When you observed IC418 with the 82", do you remember any hint of the halo? Did anyone that night make mention of it by chance?

I'm sure if it was a visual target, the 82" would show it.

And its good to see you again posting on here!! Welcome back! :)

[Paul Alsing]

Hi Dragin,

The FOV of the 82" with its largest-field eyepiece is only 5.5 arc-seconds, so no, I didn't look for or otherwise notice the halo... I see now that there is a nearly 18th mag galaxy about 1.7 arc-minute west of IC 418... I shoulda looked for that!

Jimi, when are they re-opening that Big Fellow again?

[Steve Gottlieb]

Paul, wouldn't a 31mm Nagler yield a 5 arc-minute field with the 82" at f/13.7?

As far as the halo, here's an observation that was made by Mike Kerr from Australia in 2003 with a 25-inch (63 cm) ...

Impressive planetary. Low power without a filter shows a bright, slightly oval, pink disk with a very bright central star. Spectacular view at 650x without a filter, which shows a bright, high surface brightness 14" x 12" disk, elongated N-S, with distinct bright rim and suggestions of an extremely faint halo. The rose tint is particularly noticeable in the rim below 200x but is still visible even at 350x. The thickness of the rim varies and the disk inside the rim appears grainy at 200x and 270x, slightly less so at 350x. No gain with filters but the UHC and OIII filters do confirm the presence of the faint halo, which appears to be about 40" diameter with averted vision. Best viewed at 270x or 350x without a filter, but higher magnifications also work well. (29 Jan 03)

[Paul Alsing]

Steve, yes, arc-minutes would be correct, my bad. IIRC, the eyepiece we used was an older Televue, perhaps a 41 Panoptic? All I remember is that it was the lowest-power eyepiece available. Perhaps Jimi has better details.

I just love the way Mike Kerr wrote, he was among the best ever, IMHO. He had a real gift of identifying subtle details that I never saw until I re-visited them with his report in-hand. RIP Mike.

Of course, I could say much the same of a select group of others... Steve... ;>)

[Jimi Lowrey]

Paul, They were using a old 50MM Tak. I always bring my own eyepieces when I am working up there. Most I use the 41 Pan it works great when the beast cools down.

As far as when it will reopen for public viewing I think it has been moved back to late January. I am going up there for a talk next week and will find out for sure.

[Uwe Glahn]

Very very cool object Dragan, thanks for the OOTW

I tried IC 418 once in while but the low elevation makes it difficult to detect the inner structure from a German place.

With 27" (47,5° N) and 20" (28,5° N) I noticed also a very tiny rose tint along the edges with higher AP. For me the color wasn't very striking. I remember the color of Campells Hydrogen Star as more obvious. Noticeable is the positive reaction with a Hß filter, especially along the edges.

At La Palma with 20" I noticed a faint glow around the PN (see sketch) but I explained it for me as the blooming of the bright surface PN. I don't think, that I saw the Halo.

Another very interesting detail within IC 418 is the faint shell around the CS. The "inner disk" can be seen very good at the Hubble picture. Up to now I could not see anything of that ring. Did anyone has positive observation, perhaps with bigger aperture, Jimmi, Paul?

20", 900x, NELM 7m0+
426

[Jimi Lowrey]

I looked at IC 418 last night I wanted to see if I could see the outer halo in the Image that Dragan posted. The conditions were not the best for here with high humidity and below average seeing. With a 25MM eyepiece @ 195X with a NPB filter the faint outer halo was visible with AV only. I tried several filters but got the best response with the NPB. The halo seemed to be a little brighter on the South East side. I judged the size to be around 1.6' to 1.8'. The halo looked to be round and circular with smooth edges.

[bearkite]

This has been a favorite of mine since I first observed it through Robert Werkman's Classic 18 Obsession form Dolly Sod's WV. It is actually part of my "Eye Candy" rotation during late fall/winter observing sessions. Paul mentioned the alternate name of Raspberry Nebula. I've also heard it called the Strawberry Nebula which is probably closer to how I see it.

For some reason I don't have any log entries for this object over this past winter (part of the problem of being part of an Eye Candy rotation is I generally don't log them). Was hoping to see what I had to say about this object AFTER Mr. Zambuto had worked his magic on my mirror. I know prior to the refigure, I see flashes of red that steadies to a deep red as the seeing improves. Have never really pushed the power on this as it is quite low up here in Pennsylvania. That'll have to change this coming winter. Need to spend some time to see how the improved optics affect my view.