As someone who has looked at all of these nebulas through an OIII, let me
put in my 2 cents. I have not seen the Crab look better through an OIII,
even in big dobs. Others have reported likewise. I saw the Pelican this
year at Calstar and the North American nebula several times by putting an
OIII between my eye and a pair of binoculars or a finderscope. The nebulae
were fairly obvious, especially the North American. The benefits of an OIII
are normally seen only at larger apertures, but it can also enhance a low
power small aperture view -- if the object is bright like those two nebulas.
It may be more a matter of F-ratio than aperture.
Andrew Pierce
-----Original Message-----
From: sf-bay-tac-bounces@No-Spam [mailto:sf-bay-tac-bounces@No-Spam]On
Behalf Of Richard Crisp
Sent: Tuesday, October 11, 2005 5:06 PM
To: The Astronomy Connection
Subject: Re: [TAC] re: Filter Question
well Jamie there really is [OIII] in both the Crab and the North American
Nebula and the Pelican:
Look carefully at this page dedicated to the Crab and its spectrum:
http://www.narrowbandimaging.com/crab_spectrum_page.htm
the Crab is sort of unique as it has both broadband synchrotron radiation in
the core and also has narrowband radiation in several prominent spectral
lines.
The spectrum plot on the top is very clear that [OIII] is the most abundant
species in the Crab. The data is very clear on that.
to see how the narrowband filters will block the broadband synchrotron
radiation, scroll down this page until you see the side by side comparision
of the narrowband crab with the RGB Crab.
http://www.narrowbandimaging.com/m1_crab_nebula_S2HaO3_page.htm
For the NGC7K and IC5070 look at the images below. Blue = [OIII] in these
images
http://www.narrowbandimaging.com/ngc7k_150mm_cm10_s2hao3_page.htm
http://www.narrowbandimaging.com/ngc7000_rift_s2ho3_page.htm
http://www.narrowbandimaging.com/ic5070_st10_s2hao3_page.htm
Because I sort of specialize in nebulae, I pay a lot of attention to the
spectral content of these beasts so I can find cool narrowband targets. This
is my passion at the moment in the world of imaging. Someday I will switch
to another aspect of the hobby once I shoot them all, or I will move to the
Southern Hemisphere and do the same thing there that I am doing up here :-)
----- Original Message -----
From: "Jamie Dillon" <jamie_dillon@No-Spam>
To: <sf-bay-tac@No-Spam>
Sent: Tuesday, October 11, 2005 3:58 PM
Subject: [TAC] re: Filter Question
> While right on the money about the Veil and PN's with the OIII, Crisp went
> ...
>
>>it should do a nice job on both the North American Nebula/Pelican area as
>>well as the Crab.
>
> spoken like a true imager, Richard ole pal <G>.
> An OIII won't do zilch on a dark nebula. Nor on the Crab. Matthew Marcus
> once explained that a supernova remnant, putting out synchrotron
> radiation, radiates across a broad band of visible light.
>
> Sander, meanwhile take heart, that OIII has a ton of uses. Put it on M42
> on a good night and watch details pop out.
>
>
> --
> Jamie Dillon <*> speech pathologist
> jamie_dillon@No-Spam
> "_____" -- Harpo Marx
>
Received on Tue Oct 11 17:27:06 2005