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Cosmic Challenge: IC 418
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Cosmic
Challenge:
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January 2023 |
Phil Harrington |
This month's suggested aperture range:6- to 9.25-inch (15- to 24-cm) telescopes |
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Target |
Type |
RA |
DEC |
Constellation |
Magnitude |
Size |
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IC 418 |
Planetary |
05h 27.5m |
-12° 41.8' |
Lepus |
9.6 |
12" |
If you have ever glanced at a compendium of images taken with the Hubble Space Telescope, then chances are you have seen this next challenge. You may not know it by its catalog number, IC 418, but instead may recognize it by its nickname, the Spirograph Nebula. That nickname came about because the Hubble images show an amazingly complex cloud of entangled filaments that create a strange, oval cloud that looks like it could have been drawn using a child's Spirograph toy. Remember those? You would trace intertwining arcs by rolling a color pen in a circle along the inside or outside of another circle.
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Above: Evening star map showing the location of this month's Cosmic Challenge.
Credit: Map adapted from Star Watch by Phil Harrington |
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Above: Finder chart for this month's Cosmic Challenge.
Credit: Chart adapted from Cosmic Challenge by Phil Harrington
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Despite its disk shining at magnitude 9.6, IC 418 remains an underappreciated target among amateur astronomers. Why, I don't know. It might be that there is just so much to look at in the winter sky that nobody pays much attention to a planetary nebula that even the Herschels missed during their sky surveys. That could lead some to think that any planetary listed in the Index Catalog is probably so difficult to see that they don't even try. Too bad because they are missing a nice catch.
To find IC 418, drop 4° southward from Rigel [Beta (β) Orionis] to a keystone of four 4th- and 5th-magnitude stars -- Iota (ι), Kappa (κ), Lambda (λ), and Nu (ν) Leporis. By tracing a line from Iota southeastward through Nu, and continuing that line an equal distance further beyond, you'll come right to the field of IC 418. Look for a close-set pair of 12th-magnitude stars lies just 10' to its west-northwest.
Once you have the nebula in view, switch to as high a magnification that seeing conditions will allow for the best view. My notes jotted down several years ago at the eyepiece of my 8-inch reflector at 203x evoke memories of a "small, bright disk, perhaps a greenish-gray, surrounding an obvious central star. Although clearly not a ring, averted vision suggests a darker central area adjacent to the central star, just to its north and south." The sketch below was also made at the time.
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Above: IC 418 through the author's 8-inch (20.4-cm) f/7 reflector.
Below: Hubble Space Telescope image that led to the "Spirograph Nebula" nickname. Purists still prefer to call it the "Raspberry Nebula." |
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What color is IC 418? In its most famous Hubble rendition, IC 418 shows off a burnt orange edge fading into a purplish disk. A blue inner disk surrounds the white hot progenitor star buried within. That color, however, is false, induced to accent subtle contrasts in the Spirograph-like structure.
How about you? What color do you see when you look at IC 418? Observers seem to disagree. Some, like me, see a gray disk with just a hint of a greenish tinge. Others recall a pinkish or reddish tint. The issue appears to boil down to aperture. The larger the instrument, the more distinct IC 418's ruddy hue. Magnification also plays a role. While higher magnifications are needed to see the planetary's disk, they tend to dilute any coloring. To see the reddish or pinkish effect that has led to IC 418's original nickname, the Raspberry Planetary, stick to magnifications below about 175x.
Have a favorite challenge object of your own? I'd love to hear about it, as well as how you did with this month's challenge. Contact me through my website or post to this month's discussion forum.
Remember that half of the fun is the thrill of the chase. Game on!
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About
the Author: |
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Phil Harrington's Cosmic Challenge is copyright 2023 by Philip S. Harrington. All rights reserved. No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder. |
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- Mike Allen, okiestarman56, John O'Hara and 3 others like this
29 Comments
IC 418 will always be the Raspberry Nebula to me. My first view of this interesting planetary nebula was through a 25" Dob at the 1995 Winter Star Party. IC 418's peculiar color was clearly evident.
Since then, I've observed IC 418 a number of times through various apertures. Sometimes I've seen the pinkish/reddish/purplish color. Other times I haven't. Aperture and the quality of the observing conditions certainly seem to play a role in being able to perceive it.
https://www.lcas-ast...egory=observing
Yup, it has always been "The Pink Planetary" or "The Raspberry Nebula" to me long long before some "person" took a look at the first HST image of it and gave it the name of a somewhat obscure toy. I first saw the nebula in the mid to late 1980's in a 10 inch, and I was shocked at the time with the distinct reddish hue found along its outer edge at low to moderate power. Clear skies to you.
I only discovered this nebula was visible late last summer, when it was sinking in the west.
Now if we can have some clear nights, I’ll search it when it’s high overhead.
Thanks for the article Charlie, and of course Phil.
I have a few pics of this planetary I will post.
This was taken using Firecapture 2.4 back in 2015, just when I was getting my feet wet in astro-imaging.
Taken with my new Evolution 6 and ASI533MC camera, post processing into mono.
Do any of you think I could see this through a 5 inch reflector?
Absolutely you can. I have seen this nebula multiple time before with my 6 inch dob under the murky city sky (1 inch bigger than your scope but you should be able to bag it as well). It's very bright but also tiny in size so throw as much magnification as seeing condition allow. Just be careful when searching for it, it looked pretty much like a star at low magnification.
Only one way to find out! But as TienTran@134 also advised, use moderately high magnification to make it out from surrounding stars.
Would around 50 - 70x be good? or do I need 120x?
Thats good, my skies are more suburban, still polluted, but my skies should make up for the 1 inch aperture.
To me, 75x with my 6 inch was enough to distinguish it from the surrounding stars; higher power can be use to make it look bigger. These tiny PNs usually have very noticeable bluish color which stands out in the FOV. So be careful when star hopping, you may mistake the nebula for a star. And just as PhilH said earlier the only way to find out is give it a try. Good luck
!!!
Did you use a nebula filter?
No, it was already bright enough. Although an UHC can be used to dim the stars down and makes the nebula stands out better; I haven't tried my OIII yet. But after all I preferred the unfiltered view most.
An OIII makes it stand out even better than a narrow-band "UHC-like" filter, but unless it has one of those broad "red leak" secondary passbands like the old Lumicon OIII once did, you won't see the reddish fringe around the edge of the disk. Clear skies to you.
Can I see this in a short tube 120 achro refractor?
Yes you can, but it wont be a large object in your field of view.
This guy was quite obvious in my old Tasco 3" f/15 refractor from the suburban backyard - no filter required. Stellar at less than 100x but definitely non-stellar at 160x and above. Surprisingly bright, no central star.
I took a shot at this one tonight with the 15".
To me, the nebula had a light blue color, but I did not see any red. With a UHC it stood out like a sore thumb, but it was pretty obvious without it too.
Thank you for continuing to post these challenges every month Phil!
Bagged this last night for the first time in a 12.5" dob. Thanks for the article! What a nifty little gem.
I got IC 418 tonight with my 130mm refractor. Very nice little planetary nebula and a new one for me
I found 240x worked quite well on it and the central star showed up very nicely.
Many thanks Phil
I captured this image with my eQuinox. There’s no structure visible, but it was a short exposure, and quite low in the sky. It was one of the objects on the AL’s PN list, which I completed last year. I wasn’t sure if the pink color was due to it’s being in the murk near the horizon but I guess that’s its natural hue. It’s a cool target.
Attached Thumbnails
I've seen this nebula numerous times in scopes of a great variety of apertures. I decided to take a look last night from the high desert in my 16 inch.
I was cranking up the magnification to see if I could see more detail. I was at 590x and to my surprise, I noticed a thin reddish-purple fringe around the outer edge.. I'd never seen it before, I wasn't looking for because of the small exit pupil but there it was..
Jon
Wow, I would expect color to be gone at a small exit pupil. That's cool!
I was at the Naylor Observatory on Tuesday night. After a quick look at M42 through the observatory's 17" f/15 classical Cassegrain, I located IC 418. I observed the Raspberry Nebula or the Spirograph Nebula for HST fans at 116, 170, 216, 259, 324, and 462x. The seeing wasn't all that great and neither was the transparency but IC 418's central star was easily visible. However, I didn't notice any color this time around.
A bit later while I was talking with a fellow ASH member who was observing with a 8" f/10 Celestron NexStar 8SE SCT that he purchased recently, I mentioned IC 418 and Phil's observing challenge. He wasn't familiar with the curious planetary nebula so he put it into view. The central star was visible and both he and I thought we could see the slightest hint of blue in the interior of the nebula but not the odd color around the perimeter that IC 418 is known for.
I had hoped to observe Comet C/2022 E3 (ZTF) when it rose a bit higher but clouds covered the sky earlier than I had expected and eventually I drove home.
I've included an iPhone Night mode photo of the 17" f/15 classical Cassegrain and a screen capture from SkySafari.
Attached Thumbnails
I plan to go for it tonight with my 100mm ED refractor from a dark sky site in SW Arizona. I'll post my results.