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IC 2118: The Witch Head Nebula

Explanation: Double, double toil and trouble; Fire burn, and cauldron bubble -- maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion. More formally known as IC 2118, the Witch Head Nebula glows primarily by light reflected from bright star Rigel, located just below the lower edge of the above image. Fine dust in the nebula reflects the light. The blue color is caused not only by Rigel's blue color but because the dust grains reflect blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in Earth's atmosphere are molecules of nitrogen and oxygen. The nebula lies about 1000 light-years away.

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Double, double toil and trouble - Gimmi Ratto and Davide Bardini had to suffer a lot of toil and trouble to collect enough light to produce this very fine picture of the Witch Head Nebula. Congratulations on having your picture chosen as a well-deserved Astronomy Picture of the Day!

Ann+

FYI, the date listing here is incorrectly identifying it as Jan 17th 2011 (instead of 2012) http://apod.nasa.gov/apod/
The archive listings show the right 2012 dates but the individual pages for this year are still showing "2011"

Thanks, Nightfly; the editor has been notified.

Very nice! I also like this one! http://apod.nasa.gov/apod/ap091229.html

So if the nebula is reflecting blue light, what type of filter would be helpful to observe the Nebula? Or is any necessary?

My guess is that this nebula will be very hard to observe.

Since the nebula is a reflection nebula, it reflects much of the light that hits it more or less equally. Admittedly it reflects blue light far better than red light. That still leaves a broad range of wavelengths that are reflected by this nebula. You may try to use an OIII or an H beta filter, which will let through some of the blue-green light from the nebula and block a lot of the background light, but you will still miss a lot of the light from the nebula this way.

A wide wavelength blue filter might be the best, if there are any such filters. But a problem is that many of the stars in the vicinity are blue themselves, and the blue filter will let through most of their light. So the light from the stars will overwhelm the light of the nebula, which is fairly faint anyway.

Ann

KCM wrote:
So if the nebula is reflecting blue light, what type of filter would be helpful to observe the Nebula? Or is any necessary?

You want to let light in NOT reduce it.

So why would a filter be necessary (or even desired)?

(Unless, of course, your name is Ann and you don't want to risk the possibility of seeing any red. )

neufer wrote:

KCM wrote:
So if the nebula is reflecting blue light, what type of filter would be helpful to observe the Nebula? Or is any necessary?

You want to let light in NOT reduce it.

So why would a filter be necessary (or even desired)?

(Unless, of course, your name is Ann and you don't want to risk the possibility of seeing any red. )

You've got it, Art!

Ann

Take cream in your coffee?


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Boomer12k wrote:Take cream in your coffee?

And jam on your brakes?

I'll pass on the brakes, owlice-but how about toast? Or even better, a muffin?

I think this is a very interesting image. I need to start looking for these objects myself, if it isn't so cold.

G'day all.
Pardon my ignorance here but I cannot, for the life of me, identify the "witches head" in this APOD?
Should I be standing on my head to see it, or perhaps on my left ear (yes, I've tried both!) but still can't seem to see anything resembling a witch...
Thanks in advance.

The nose of the witch is the bluest protrusion pointing down in the middle of the picture. To the left of the nose is a "wavy line" which is the upper lip, the open mouth and the lower lip of the witch. (The witch has a large yellow "pimple", a bright yellow star, on her upper lip.) At lower left if the witch's chin. Her forehead and hat are presumably at upper right.

Ann

wbd wrote:G'day all.
Pardon my ignorance here but I cannot, for the life of me, identify the "witches head" in this APOD?
Should I be standing on my head to see it, or perhaps on my left ear (yes, I've tried both!) but still can't seem to see anything resembling a witch...
Thanks in advance.

Try standing on your RIGHT ear..... Or just tilt your head to the right and (hopefully) the witch's profile will become apparent.

Thanks for that explanation - I can now see some semblance of a witch's head... just!