I don't know how that works: not all of the light rays are angled....

Astrodon says lots of things including things that are mutually contradictory;
depending on what he has for sale based on my experience dealing with that guy.
I never believe anything he says.



-----Original Message-----
From: ssb73q
Sent: Oct 20, 2009 10:39 AM
To: Astroimaging_filters@yahoogroups.com
Subject: [Astroimaging_filters] Re: Anybody here using a HeII filter??





Hi Richard, I noticed that AstroDon says he shifts his filters somewhat to the
red to compensate for fast optical systems. He claims that other manufacturers
also do that. My Baader filters seem to be so designed. If your very narroband
filter was designed that way, there's little room for any astronomical blue
shift.

Regards,
Richard
The Bunkroom Observatory

--- In Astroimaging_filters@yahoogroups.com, Richard Crisp <rdcrisp@...> wrote:
>
> mine has a 4.5nm stated bandpass
>
> I have used it with success on M57, M27, NGC7635 and M42
>
> I plan to try with Thor's Helmet when it comes into position
>
> I had no success with NGC6888. It may be due to a doppler shift as you suggest
or it may be due to some other reason
>
>
>
> -----Original Message-----
> From: ssb73q
> Sent: Oct 20, 2009 9:48 AM
> To: Astroimaging_filters@yahoogroups.com
> Subject: [Astroimaging_filters] Re: Anybody here using a HeII filter??
>
>
>
>
>
> Hi Richard, I have been doing a little reading where gas being expelled from
Wolf-Rayet stars can exceed ~4000 km/s. That could cause a spectral shift of
~2.5nm. Too narrow a HeII filter may miss much of the outflow gas.
>
> Regards,
> Richard
> The Bunkroom Observatory
>
> --- In Astroimaging_filters@yahoogroups.com, "Richard Crisp" <rdcrisp@> wrote:
> >
> > 4.5nm
> >
> >
> > ----- Original Message -----
> > From: ssb73q
> > To: Astroimaging_filters@yahoogroups.com
> > Sent: Thursday, October 08, 2009 12:07 PM
> > Subject: [Astroimaging_filters] Re: Anybody here using a HeII filter??
> >
> >
> > Hi Richard, one additional thought. What is the bandpass of your HeII
filter? Gas maybe being expelled from the Wolf so fast that your narrow bandpass
HeII misses the blueshifted HeII?
> >
> > Regards,
> > Richard
> > The Bunkroom Observatory
> >
> > --- In Astroimaging_filters@yahoogroups.com, "ssb73q" <ssb73q@> wrote:
> > >
> > > Hi Richard, as you point out, ngc6888 (crescent nebula) has Wolf Rayet 7.4
magnitude star WR136. See the spectra:
> > > http://www.astrosurf.com/~buil/us/peculiar2/wolf.htm#WR136
> > >
> > > Lots of HeII. I look forward to your results trying to image it again.
> > >
> > > Regards,
> > > Richard
> > > The Bunkroom Observatory
> > >
> > >
> > > --- In Astroimaging_filters@yahoogroups.com, "Richard Crisp" <rdcrisp@>
wrote:
> > > >
> > > > I tried it on the crescent, and it has a Wolf Rayet star. I didn't see
any action in the data but I may give it a half hour with high binning to try
one more time before declaring it devoid of HeII
> > > >
> > > > I plan to try Thor's helmet too, since it also has a wolf rayet star
> > > >
> > > > I forgot to mention that I tried the Orion nebula and got signal
> > > >
> > > >
http://www.narrowbandimaging.com/m42_ap180edt_f9_ml4022_cs_s2hao3_page.htm
> > > >
> > > > Because it looks pretty different than the essentially spherical shells
surrounding the white dwarfs in the PNe, I am suspicious I may be seeing some
broadband light coming through at that wavelength. Spectroscopic data would nail
it for sure
> > > >
> > > > It takes very high energy to create the HeII line at 468nm so it stands
to reason that it would appear spherical and close-in to the white dwarfs. So I
am unconvinced either way on M42: simply needs more investigation
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: ssb73q
> > > > To: Astroimaging_filters@yahoogroups.com
> > > > Sent: Thursday, October 08, 2009 10:47 AM
> > > > Subject: [Astroimaging_filters] Re: Anybody here using a HeII filter??
> > > >
> > > >
> > > > Hi Richard, very interesting! There's a lot of information on HeII in
your images. Seems to be one of the last elements blown off the star. I'm going
to get a HeII ($84 Thorlabs 10nm 470nm filter) and give it a try. Of course it
won't have the % transmission or narrowband of your filter, but it'll be worth a
try.
> > > >
> > > > I have also been considering OI to be used on PNe. What do you think
about OI (6300A)?
> > > >
> > > > Regards,
> > > > Richard
> > > > The Bunkroom Observatory
> > > >
> > > > --- In Astroimaging_filters@yahoogroups.com, "Richard Crisp" <rdcrisp@>
wrote:
> > > > >
> > > > > of course!
> > > > >
> > > > >
> > > > >
http://www.narrowbandimaging.com/m27_ap180edt_f9_ml4022_cs_HaO3HeliumII_page.htm
> > > > >
> > > > >
http://www.narrowbandimaging.com/ngc7293_ap180edt_ml4022_cshao3he2_page.htm
> > > > >
> > > > >
http://www.narrowbandimaging.com/m57_mk1sn2_hao3he2_luminance_schillings_crisp_p\
age.htm
> > > > >
> > > > > who else would be using one except for me Richard?
> > > > >
> > > > > It is most effectively used when you have hot stars such as found as
the central star in many Planetary Nebulae
> > > > >
> > > > >
> > > > > ----- Original Message -----
> > > > > From: ssb73q
> > > > > To: Astroimaging_filters@yahoogroups.com
> > > > > Sent: Thursday, October 08, 2009 8:37 AM
> > > > > Subject: [Astroimaging_filters] Anybody here using a HeII filter??
> > > > >
> > > > >
> > > > > Hi, I see a lot of HeII (4686A) in planetary nebula and I understand
that HeII filters are used for finding Wolf-Rayet stars.
> > > > >
> > > > > Is there anybody here currently using a HeII filter?
> > > > >
> > > > > Regards,
> > > > > Richard
> > > > > The Bunkroom Observatory
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > [Non-text portions of this message have been removed]
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > >
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>