Alternatives to the Hubble Palette

Alternatives to the Hubble Palette

The Great Orion Nebula (M42, NGC 1976) is probably the brightest, most
famous and most imaged nebula in the night sky. About 1,500 light
years away, M42 is a very active and turbulent cloud of gas and dust
and an important star forming region.. There are many hot young stars
(most notably the Trapezium stars which can be seen clearly in these
images) which ionise the surrounding gas. There is also a significant
amount of reflected light which contributes to the wide range of
visible colours.

http://www.martin-nicholson.info/cfh...lepalette3.htm


Martin Nicholson, Daventry, England.
http://www.martin-nicholson.info/1/1a.htm
Visit the Astronomical Hall of Shame at http://www.geocities.com/queen5658/

here's another way to mix the so called Hubble Palette for M42, Martin

http://www.narrowbandimaging.com/m42...2hao3_page.htm

unfortunately the seeing wasn't especially good when I took that image. It
is really nice when the seeing is good when using that 18" f/12.6 classical
cass...

On the processing, part of the trick is to stretch each channel
independently so that the full extent of the dynamic range is used by the
histogram. That gives you the full gamut of the color range.

your Hubble image of M42 is completely dominated by the hydrogen signal and
it should be since it is about an order of magnitude more abundant than the
other species. You can solve that by histogram stretching.

Part of the reason why many of my images run for 20-30 hours is to get
sufficient signal in the Sulfur and Oxygen channels so that they can be
properly stretched in order to accomplish the histogram manipulations I
mentioned above. Without a lot of signal in the Image, The Darks and The
Flats, you can get a noisy mess on your hands after aggressive stretching.
Don't overlook the importance of high S/N flats and high S/N darks too. They
are all important.

Some of these objects simply are not for the faint of heart: Jones 1 comes
to mind in that regard: you need tons of exposure time to shoot it in
emission line at long focal length.

rdc



"ukastronomy" wrote in message
oups.com...
Alternatives to the Hubble Palette

The Great Orion Nebula (M42, NGC 1976) is probably the brightest, most
famous and most imaged nebula in the night sky. About 1,500 light
years away, M42 is a very active and turbulent cloud of gas and dust
and an important star forming region.. There are many hot young stars
(most notably the Trapezium stars which can be seen clearly in these
images) which ionise the surrounding gas. There is also a significant
amount of reflected light which contributes to the wide range of
visible colours.

http://www.martin-nicholson.info/cfh...lepalette3.htm


Martin Nicholson, Daventry, England.
http://www.martin-nicholson.info/1/1a.htm
Visit the Astronomical Hall of Shame at
http://www.geocities.com/queen5658/

Thank you for sharing your thoughts and experiences on narrow band
imaging.

One of reasons I have for posting to the astro groups is to hear from
the experts - such as yourself - which then has the added bonus of
improving to signal to noise rating within the group. The percentage
of non-astronomical spam goes down!

Martin Nicholson, Daventry, England.

Visit the Astronomical Hall of Shame at
http://www.geocities.com/queen5658/



On 6 Nov, 03:39, "Richard Crisp" wrote:
here's another way to mix the so called Hubble Palette for M42, Martin

http://www.narrowbandimaging.com/m42...2hao3_page.htm

unfortunately the seeing wasn't especially good when I took that image. It
is really nice when the seeing is good when using that 18" f/12.6 classical
cass...

On the processing, part of the trick is to stretch each channel
independently so that the full extent of the dynamic range is used by the
histogram. That gives you the full gamut of the color range.

your Hubble image of M42 is completely dominated by the hydrogen signal and
it should be since it is about an order of magnitude more abundant than the
other species. You can solve that by histogram stretching.

Part of the reason why many of my images run for 20-30 hours is to get
sufficient signal in the Sulfur and Oxygen channels so that they can be
properly stretched in order to accomplish the histogram manipulations I
mentioned above. Without a lot of signal in the Image, The Darks and The
Flats, you can get a noisy mess on your hands after aggressive stretching.
Don't overlook the importance of high S/N flats and high S/N darks too. They
are all important.

Some of these objects simply are not for the faint of heart: Jones 1 comes
to mind in that regard: you need tons of exposure time to shoot it in
emission line at long focal length.

rdc

"ukastronomy" wrote in message

oups.com...



Alternatives to the Hubble Palette

The Great Orion Nebula (M42, NGC 1976) is probably the brightest, most
famous and most imaged nebula in the night sky. About 1,500 light
years away, M42 is a very active and turbulent cloud of gas and dust
and an important star forming region.. There are many hot young stars
(most notably the Trapezium stars which can be seen clearly in these
images) which ionise the surrounding gas. There is also a significant
amount of reflected light which contributes to the wide range of
visible colours.

http://www.martin-nicholson.info/cfh...lepalette3.htm

Martin Nicholson, Daventry, England.
http://www.martin-nicholson.info/1/1a.htm
Visit the Astronomical Hall of Shame at
http://www.geocities.com/queen5658/- Hide quoted text -

- Show quoted text -

you are more than welcome Martin

Here's an article I wrote on the subject a few years back

when I read it now I realize there's much more to add but it is a good
starting point

http://www.narrowbandimaging.com/tri...crisp_page.htm

Your images are definitely on the right path but it looks to me that a few
basic things can be improved

the key ones are flats look to be problematic and then there's the exposure
time/stretching issue I previously mentioned

For flats, the most important things are

1) no light leaks if you shoot in the daylight like i do

2) keeping the same level of exposure frame to frame (usually I adjust
exposure time to do that at evening twilight)

3) getting sufficient numbers of flats. To get the best results you need
about 1million electrons in the flat data set at a minimum

Much less than that and your flats will contribute to the noise of the
image. The goal is to have shot -noise limited performance from the
transistion from read noise limited all the way to full well.

here's a bit more on that:

http://www.narrowbandimaging.com/noi...flats_page.htm

http://www.narrowbandimaging.com/fix...noise_page.htm


note that unless flats are used you have three distinct regimes of
operation: read noise limited, shot noise limited, fixed pattern noise
limited.

the flats remove the fixed pattern noise limit which otherwise occurs when
the PhotoResponseNonUniformity* signal level (electrons) SQRT(signal) [in
electrons]

for a 1% PRNU spec, that works out to be 10,000 electrons: above that and
you will be FPN limited and below it and above the Read noise limit, you are
Shot noise limited


"ukastronomy" wrote in message
oups.com...
Thank you for sharing your thoughts and experiences on narrow band
imaging.

One of reasons I have for posting to the astro groups is to hear from
the experts - such as yourself - which then has the added bonus of
improving to signal to noise rating within the group. The percentage
of non-astronomical spam goes down!

Martin Nicholson, Daventry, England.

Visit the Astronomical Hall of Shame at
http://www.geocities.com/queen5658/



On 6 Nov, 03:39, "Richard Crisp" wrote:
here's another way to mix the so called Hubble Palette for M42, Martin

http://www.narrowbandimaging.com/m42...2hao3_page.htm

unfortunately the seeing wasn't especially good when I took that image.
It
is really nice when the seeing is good when using that 18" f/12.6
classical
cass...

On the processing, part of the trick is to stretch each channel
independently so that the full extent of the dynamic range is used by the
histogram. That gives you the full gamut of the color range.

your Hubble image of M42 is completely dominated by the hydrogen signal
and
it should be since it is about an order of magnitude more abundant than
the
other species. You can solve that by histogram stretching.

Part of the reason why many of my images run for 20-30 hours is to get
sufficient signal in the Sulfur and Oxygen channels so that they can be
properly stretched in order to accomplish the histogram manipulations I
mentioned above. Without a lot of signal in the Image, The Darks and The
Flats, you can get a noisy mess on your hands after aggressive
stretching.
Don't overlook the importance of high S/N flats and high S/N darks too.
They
are all important.

Some of these objects simply are not for the faint of heart: Jones 1
comes
to mind in that regard: you need tons of exposure time to shoot it in
emission line at long focal length.

rdc

"ukastronomy" wrote in message

oups.com...



Alternatives to the Hubble Palette

The Great Orion Nebula (M42, NGC 1976) is probably the brightest, most
famous and most imaged nebula in the night sky. About 1,500 light
years away, M42 is a very active and turbulent cloud of gas and dust
and an important star forming region.. There are many hot young stars
(most notably the Trapezium stars which can be seen clearly in these
images) which ionise the surrounding gas. There is also a significant
amount of reflected light which contributes to the wide range of
visible colours.

http://www.martin-nicholson.info/cfh...lepalette3.htm

Martin Nicholson, Daventry, England.
http://www.martin-nicholson.info/1/1a.htm
Visit the Astronomical Hall of Shame at
http://www.geocities.com/queen5658/- Hide quoted text -

- Show quoted text -