Chuck and Kim, My experience has been that O3 filters are of little help with many planetary nebula, a consensus on wether it helped with the Helix did not occur at SPOC with many experienced SLAS observers last year. It is kind of large for the Grims' general field of view. The best views come from smaller lower magnification scopes (IE <32"). In the case of the helix, I read (from a google search) that expelled gases from the red giant can travel at different rates and have different temperatures, so they become illuminated by mixing gases of different temperatures, and form some comet like patches that could perhaps from pluto size objects. The Helix is the closest of the planetary nebulas, so I imagine more subtle illumination can be seen. It does seem the very definition of a planetary is an emission nebula with its primary illumination coming from a White Dwarf. Erik --- kimharch@cut.net wrote: From: "Kim" <kimharch@cut.net> To: "'Utah Astronomy'" <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] White dwarfs and YOU Date: Sun, 25 Jan 2009 20:51:55 -0700 Like you, Chuck, I haven't had the time to do any immediate research, but I seem to recall that the radiation energy (what radiation I can't say - I'm no physicist, either) that causes the pn to be visible is ionizing radiation causing the pn to emit light from O3 emissions - therefore, not merely a reflection phenomena, but I’m certain that could also be a component. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Sunday, January 25, 2009 8:18 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] White dwarfs and YOU No, I didn't mention that. Jerry was the one who posted about the visibility of white dwarfs in a cataclysmic variable system, not Bishop. I was attempting to distance that from Bishop and try to underline the differences. In my post, Bishop's comments were in quotes, mine were not. Sorry for the apparent confusion. Also, I need to research this, but I'm not sure that planetary nebula are illuminated by the central star, but by the expelled material colliding with material ejected previously. These are glowing, ionized nebula, not merely reflection nebula. On Sun, Jan 25, 2009 at 8:05 PM, <zaurak@digis.net> wrote:
You also mention that he is talking about white dwarfs from cataclysmic double stars. Perhaps in the case of planetary nebula (I believe most of these are not from cataclysmic doubles), that there is nothing to see until the "life" of White Dwarf is turned on, to illuminate the gases expelled from the red giant. Simply the intermediate period is before the nebula is visible. Again, I imagine most white dwarfs are not the product of double star systems gone wrong.
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