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Cosmic Challenge: IC 418

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Cosmic Challenge:
IC 418


January 2023

Phil Harrington

This month's suggested aperture range:

6- to 9.25-inch (15- to 24-cm) telescopes












IC 418


05h 27.5m

-12° 41.8'





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.


Above: Evening star map showing the location of this month's Cosmic Challenge.


Credit: Map adapted from Star Watch by Phil Harrington


Above: Finder chart for this month's Cosmic Challenge.


Credit: Chart adapted from Cosmic Challenge by Phil Harrington
Click on the chart to open a printable PDF version in a new window



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.

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."


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!

About the Author:

Phil Harrington writes the monthly Binocular Universe column in Astronomy magazine and is the author of 9 books on astronomy.  Visit his web site at www.philharrington.net to learn more.

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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