Re: (IAAC) IC 434 - 17.5inch F/4.5

• To: Internet Amateur Astronomers Catalog - Discussion <netastrocatalog-announce@latrade.com>
• Subject: Re: (IAAC) IC 434 - 17.5inch F/4.5
• From: Lew Gramer <dedalus>
• Date: Tue, 03 Nov 98 14:33:54 -0500
• In-Reply-To: Your message of "Tue, 03 Nov 98 19:47:44 +0200." <l03020702b26489b0b690@[134.157.81.187]>
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• Sender: owner-netastrocatalog-announce

Again thanks for these fine observations, Yann. BTW, bravo on catching
the single useful hour of darkness between moonset and dawn yesterday!
Also, I was curious about IC 466 - you mention it contains both refl-
ection and emission features, and yet its appearance only changed at
the very edge when using emission-band filters. What can be concluded
about the physics inside this nebula from this visual effect?


And now for the Dumb Amateur Astrophysics Question of the Week...

I have always been curious as to the astrophysical explanation behind
the narrow H-beta emission spectra of a few certain nebulae in the sky:
these include the "H-beta four" nebulae which traditionally justify the
use (and so purchase) of an H-beta filter versus an OIII or UHC. Why do
these nebulae (e.g., IC434 around the Horsehead, or the California) emit
so exclusively and narrowly in the Hydrogen beta band?

Lew

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• Re: (IAAC) IC 434 - 17.5inch F/4.5
• From: Owen Brazell <owen@online.rednet.co.uk>

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