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View Full Version : ASTRO: Finally finished: Thor's Helmet in [SII], Ha and [OIII]


Richard Crisp
January 24th 04, 01:51 AM
The seeing was terrible for two of the past three nights, but I'll take
clear skies and bad seeing over cloudy skies, especially after three weeks
of the Seattle Nebula, a large naked-eye object figuring prominently in both
the daytime and night skies.

Anyway, being work nights, I had to shut down pretty early so it took a few
nights to gather up the 4 hours and 20 minutes worth of data.

I used my C14 at f/12.46 and FLI Dream Machine camera.

The sub exposures were all 20 minutes, and I took three through Ha, and five
through each [SII] and [OIII]

I wish the seeing had been better but I am tired of this object and will
just move on.

http://www.rdcrisp.darkhorizons.org/ngc2359_thor_s2hao3_page.htm

who knows, I may gather up some more data before it goes out of season, but
for now I think I am finished with it.

Richard

Bill Meyers
January 24th 04, 02:27 AM
Another great picture! Thank you,
Bill Meyers

Richard Crisp wrote:

> The seeing was terrible for two of the past three nights, but I'll take
> clear skies and bad seeing over cloudy skies, especially after three weeks
> of the Seattle Nebula, a large naked-eye object figuring prominently in both
> the daytime and night skies.
>
> Anyway, being work nights, I had to shut down pretty early so it took a few
> nights to gather up the 4 hours and 20 minutes worth of data.
>
> I used my C14 at f/12.46 and FLI Dream Machine camera.
>
> The sub exposures were all 20 minutes, and I took three through Ha, and five
> through each [SII] and [OIII]
>
> I wish the seeing had been better but I am tired of this object and will
> just move on.
>
> http://www.rdcrisp.darkhorizons.org/ngc2359_thor_s2hao3_page.htm
>
> who knows, I may gather up some more data before it goes out of season, but
> for now I think I am finished with it.
>
> Richard

Stefan Lilge
January 24th 04, 12:42 PM
Richard,

beautiful and interesting image. You certainly don't take "snapshots" with
all the time you spend on one object.

Stefan

"Richard Crisp" > schrieb im Newsbeitrag
om...
> The seeing was terrible for two of the past three nights, but I'll take
> clear skies and bad seeing over cloudy skies, especially after three weeks
> of the Seattle Nebula, a large naked-eye object figuring prominently in
both
> the daytime and night skies.
>
> Anyway, being work nights, I had to shut down pretty early so it took a
few
> nights to gather up the 4 hours and 20 minutes worth of data.
>
> I used my C14 at f/12.46 and FLI Dream Machine camera.
>
> The sub exposures were all 20 minutes, and I took three through Ha, and
five
> through each [SII] and [OIII]
>
> I wish the seeing had been better but I am tired of this object and will
> just move on.
>
> http://www.rdcrisp.darkhorizons.org/ngc2359_thor_s2hao3_page.htm
>
> who knows, I may gather up some more data before it goes out of season,
but
> for now I think I am finished with it.
>
> Richard
>
>

Richard Crisp
January 24th 04, 03:04 PM
Thanks for taking the time to comment Stefan.

You are right, it is hard to do these shots very fast for me. I am imaging
using my C14 without a focal reducer. With the very long imaging train I am
using, it affects the focal length of the scope. I had measured it using
Image Link in The Sky and determined it to be f/12.46 focal ratio or
F=4430mm. That is a bit slower than the stock f/11, F=3910 Celestron quotes.

Anyway that certainly makes for longer exposures, but it does let me go for
some smallish objects.

The other major factor is that I am using 3nm FWHM emission line filters and
they really reduce the light intensity quite a lot, even in the passband.
Making matters worse is the fact that the light must first go through a "hot
mirror" in my beam splitter before it even goes into the filter. The
dichroic Hot Mirror also has a light loss associated with it.

So those are the key reasons the exposures tend to be long.

I should try Thor's Helmet using my AP155EDF and my ST10XME with the same
filters sometime and compare. But I just love my Dream
Machine/C14/BeamSplitter AO7 rig....

Richard


"Stefan Lilge" > wrote in message
...
> Richard,
>
> beautiful and interesting image. You certainly don't take "snapshots" with
> all the time you spend on one object.
>
> Stefan
>
> "Richard Crisp" > schrieb im Newsbeitrag
> om...
> > The seeing was terrible for two of the past three nights, but I'll take
> > clear skies and bad seeing over cloudy skies, especially after three
weeks
> > of the Seattle Nebula, a large naked-eye object figuring prominently in
> both
> > the daytime and night skies.
> >
> > Anyway, being work nights, I had to shut down pretty early so it took a
> few
> > nights to gather up the 4 hours and 20 minutes worth of data.
> >
> > I used my C14 at f/12.46 and FLI Dream Machine camera.
> >
> > The sub exposures were all 20 minutes, and I took three through Ha, and
> five
> > through each [SII] and [OIII]
> >
> > I wish the seeing had been better but I am tired of this object and will
> > just move on.
> >
> > http://www.rdcrisp.darkhorizons.org/ngc2359_thor_s2hao3_page.htm
> >
> > who knows, I may gather up some more data before it goes out of season,
> but
> > for now I think I am finished with it.
> >
> > Richard
> >
> >
>

Tristan DiLapo
January 25th 04, 01:36 AM
Hi Richard,

A very spectacular image! Congratulations. However, I'm somewhat
confused about your technique. You're using the Sulfur II filter for the
red component, the Hydrogen Alpha for green and Oxygen III for the blue.
I would assume the H-alpha would be red, OIII for green and SII for
blue. What's the "rational" behind your choices?

Thanks,

Tristan

Richard Crisp wrote:
> The seeing was terrible for two of the past three nights, but I'll take
> clear skies and bad seeing over cloudy skies, especially after three weeks
> of the Seattle Nebula, a large naked-eye object figuring prominently in both
> the daytime and night skies.
>
> Anyway, being work nights, I had to shut down pretty early so it took a few
> nights to gather up the 4 hours and 20 minutes worth of data.
>
> I used my C14 at f/12.46 and FLI Dream Machine camera.
>
> The sub exposures were all 20 minutes, and I took three through Ha, and five
> through each [SII] and [OIII]
>
> I wish the seeing had been better but I am tired of this object and will
> just move on.
>
> http://www.rdcrisp.darkhorizons.org/ngc2359_thor_s2hao3_page.htm
>
> who knows, I may gather up some more data before it goes out of season, but
> for now I think I am finished with it.
>
> Richard
>
>

Richard Crisp
January 25th 04, 05:55 AM
"Tristan DiLapo" > wrote in message
...
> Hi Richard,
>
> A very spectacular image! Congratulations. However, I'm somewhat
> confused about your technique. You're using the Sulfur II filter for the
> red component, the Hydrogen Alpha for green and Oxygen III for the blue.
> I would assume the H-alpha would be red, OIII for green and SII for
> blue. What's the "rational" behind your choices?
>


Hi Tristan

Gee since the colors are "false color" almost any way will do I suppose. I
used the color assignment that I did to arrange the emission lines in
strictly descending wavelength starting with the longest, [SII] (673.4nm).
The next would be Hydrogen Alpha at 656.3nm. Then last would be [OIII] at
500.7nm

By the way the famous Hubble shot "Pillars of Creation", which is a shot of
the Star Queen in the middle of M16, was shot using exactly the same filters
in exactly the same color assignment. For that reason I call that palette
the "Pillars Palette".

I shot the Pillars once using that palette:
http://www.rdcrisp.darkhorizons.org/m16_in_sulfur_ii_page.htm

I also have used the color assignment you suggested: Red = Hydrogen Alpha,
Green = Oxygen III and blue = Sulfur II.

I agree, it gives the Hydrogen and Oxygen their familar colors, and Sulfur,
which is really redder than Halpha, is just left over and assigned to Blue.
I used that with my Rosette Nebula some time back. Turns out the CFHT
observatory in Hawaii used that particular color assignment when they shot
their Rosette. I therfore call that color palette the "CFHT Palette".

Here is that Rosette in the CFHT palette:
http://www.rdcrisp.darkhorizons.org/ngc2244_rosette_cfht_page.htm

Of course the color assignments are somewhat arbitrary, but those are the
ones I have used.

Richard