The big Kahuna

[Octane (Humayun)]

alpal,

There's a reason why people get their DSLRs modified -- to give them a similar spectral response as monochrome CCDs. You need to stop worrying about what your camera shows you in the blue channel (oxygen emission). DSLRs are designed as primarily terrestrial imaging devices. Astrophotographic CCDs are designed to capture as much of the spectrum as possible. What you're seeing is scientific but, with a big splash of subjective creativity.

Once you get over the hurdle of not seeing what you see in /your/ images, you'll want to get your camera modified, or buy a CCD that isn't limited by an IR/UV blocker filter.

H

[alpal]

Peter,

If being pink makes you happy, then so be it.

Accurate? I'll go with David's rendition.

Actually it's going blue.

I have been affected by watching Ken Crawford's videos
on digging out the details.

First of all I thought it was cheating but then I thought -
why not do it with colour too?
If there is a colour information that allows you to see detail that
would otherwise be invisible - then accentuate it!
It's really a matter of taste & trying to get the most out of data.

David's rendition is your taste & is of course more accurate.

It's all good fun - anyway!

[alpal]

Originally Posted by Octane

alpal,

There's a reason why people get their DSLRs modified -- to give them a similar spectral response as monochrome CCDs. You need to stop worrying about what your camera shows you in the blue channel (oxygen emission). DSLRs are designed as primarily terrestrial imaging devices. Astrophotographic CCDs are designed to capture as much of the spectrum as possible. What you're seeing is scientific but, with a big splash of subjective creativity.

Once you get over the hurdle of not seeing what you see in /your/ images, you'll want to get your camera modified, or buy a CCD that isn't limited by an IR/UV blocker filter.

H

Don't worry ,
I'm researching cameras every day.
I just can't decide which one to buy.
I will however go it alone on processing if need be.
I like to dig out colour detail.

[Peter Ward]

Originally Posted by alpal

Don't worry ,
I'm researching cameras every day.
I just can't decide which one to buy.
I will however go it alone on processing if need be.
I like to dig out colour detail.

As you should!

I've made a few tweaks... including a just tad more blue

[alpal]

That's much better & a larger picture too!
I can make out different detail now.

[Peter.M]

If realism is what your looking for Alpal, Hydrogen typically ionises between 5000 and 10000 kelvin. So if we were out in space and could view it with our own eyes I can assure you we would be vaporised, along with any DSLR we took with us.

[alpal]

Originally Posted by Peter.M

If realism is what your looking for Alpal, Hydrogen typically ionises between 5000 and 10000 kelvin. So if we were out in space and could view it with our own eyes I can assure you we would be vaporised, along with any DSLR we took with us.

Sure - but the DSLR camera is made to match the human eye
so that the pictures of say people's faces look real.
If the DSLR says there is blue there -
then blue is there.
Anyway - great job - your optics are perfect - you'd
have to be very proud of that last pic.
The FOV is huge & I could only dream of doing that.

[Peter.M]

The DSLR is made to match the human eye on earth, and unfortunately a sensor does not discriminate between NIR and visible photons. Anything with a temperature will emit black body radiation in the NIR and this is what the cameras filter is there to block (otherwise our photos would all look like they were taken from a COPS helicoptor), unfortunately the filter does not stop sharply where NIR becomes visible, and this causes low QE for the longer wavelegnths.

The human eye percieves red and blue relatively poorly as shown here.

http://en.wikipedia.org/wiki/File:Eyesensitivity.png

[TrevorW]

Nice tweaking Peter, there appears to be better definition in the core and little more colour depth but I'm now viewing this on my home monitor

[alpal]

Originally Posted by Peter.M

The DSLR is made to match the human eye on earth, and unfortunately a sensor does not discriminate between NIR and visible photons. Anything with a temperature will emit black body radiation in the NIR and this is what the cameras filter is there to block (otherwise our photos would all look like they were taken from a COPS helicoptor), unfortunately the filter does not stop sharply where NIR becomes visible, and this causes low QE for the longer wavelegnths.

The human eye percieves red and blue relatively poorly as shown here.

http://en.wikipedia.org/wiki/File:Eyesensitivity.png

That just proves that if there is plenty of blue
& red in the DSLR histogram then those colours are
in reality actually quite bright.
In fact even brighter as the Bayer Matrix has 2 greens for every red or blue pixel.


I think the processing theory is correct if a DSLR palette is used
& enhanced for the dynamic range of all colours to dig out
that little bit more detail than the eye can see.
Also you can get a situation where if the Ha narrowband is used for
luminance then the colours end up all wrong.

Certainly if we look at the Hubble Palette the 3 colour narrow band photo
is being deliberately used to give that detail that would otherwise be unseen.

In the same way microwave radio pictures can be built up with colour.

[troypiggo (Troy)]

Originally Posted by alpal

Certainly if we look at the Hubble Palette the 3 colour narrow band photo
is being deliberately used to give that detail that would otherwise be unseen.

In the same way microwave radio pictures can be built up with colour.

Sounds like you're confusing what part of the spectrum of light is hitting the sensor vs what is displayed on screen here. With Hubble palette, 2 of the 3 color channels are from red spectrum light. To represent those 2 reds on screen we put them in the R and G channel of the final image.

As H said, you need to change your thinking. Separate what the sensor is receiving from what the image displays.

[Peter.M]

You are assuming that you are correct about DSLR being the same as a human eye, and then using that assumption to prove your own point. That logic is a fundamental mistake when evaluating any scientific hypothesis.

The human eyes insensitivity to red and blue can be proven when visually looking at these nebula as they apear greyscale ( I know due to rods). What this dosent prove is that an exposure with a DSLR with more blue than red saturation is a linear representation of the concentration of blue light hitting the camera from that object. Because some of the red is blocked by the IR filter.

I will leave it at this, because I feel like I am hijacking Petes thread. This is a beautiful representation of the object regardless of what colour people think it should be.

[marc4darkskies (Marcus)]

Originally Posted by Peter Ward

I've made a few tweaks... including a just tad more blue

Now you're talking Peter!! Very nice!

[Paul Haese]

Originally Posted by Peter Ward

Appreciate your frank comments Paul.

If by punch you mean: some sort of sharpening... decided to keep it "au naturel ". As you say, dealers choice. But I might fiddle at the edges at tad.

I wont bore interested viewers by heralding the changes, they'll just happen from time to time.

Another object!? What? move away from the program??

Yes, I think it's time to move on. 3576 I've decided looks poor in wide field NB. RGB seems to be the go

As for when...Did I mention the forecast again today???

No not sharpening it was probably more to do with contrast in the original image. I guess I really like high contrast images, but that as you know has to be balanced against the dreaminess (er gaseous nature) of the nebulosity. Your latest version certainly has a lot more contrast in the surrounding nebula and out skirts (especially like the top left of the image which is lovely), but the key hole looks washed out or flat a little to me.

Yeah I hear you about weather. Our turn now. Must have been something I said. Serves me right.

[cventer]

Wow Peter just lovely. Just catching up on this with color added. That STX16803 and scope are a winner of a combination. And o course the processing is excellent as well.

I just put an offer on an unsused STX16803 on Astromart but the seller wont bite. Only wants to ship inside USA :-(

[gregbradley]

Perhaps the most exquisite stars I recall seeing in an astrophotograph.
For that alone the scope was worth the price.

Overall a fabulous image. Flawless.

Greg.

[Peter Ward]

Originally Posted by gregbradley

Perhaps the most exquisite stars I recall seeing in an astrophotograph.
For that alone the scope was worth the price.

Overall a fabulous image. Flawless.

Greg.

Thanks Greg. Very kind. Went with a totally different layered masking technique to blend the Halpha. Seems to have worked

Originally Posted by cventer

Wow Peter just lovely. Just catching up on this with color added. That STX16803 and scope are a winner of a combination. And o course the processing is excellent as well.

I just put an offer on an unsused STX16803 on Astromart but the seller wont bite. Only wants to ship inside USA :-(

They are a superb camera with the RHA, as the off axis Guide stars are pristine dots and very easy to guide on even in SII.

Originally Posted by Paul Haese

No not sharpening it was probably more to do with contrast in the original image. I guess I really like high contrast images, but that as you know has to be balanced against the dreaminess (er gaseous nature) of the nebulosity. Your latest version certainly has a lot more contrast in the surrounding nebula and out skirts (especially like the top left of the image which is lovely), but the key hole looks washed out or flat a little to me.

Yeah I hear you about weather. Our turn now. Must have been something I said. Serves me right.

yep for me weather and work.... Now north of the equator for a bit.
Re: the keyhole, as one David Malin puts it, "respect the light". Unfortunately doing so means it will be bright and lacking contrast... Which is not to say I can't mask it off for a disrespectful version

Originally Posted by marc4darkskies

Now you're talking Peter!! Very nice!

Thanks Marcus. I think I'm bumbling along to a version I'll finally be happy with

[cventer]

Originally Posted by Peter Ward

Thanks Greg. Very kind. Went with a totally different layered masking technique to blend the Halpha. Seems to have worked

Peter dont hold out on us. This is allways a real challenge. Love to hear about how you went about the Ha blend.

[Peter Ward]

Originally Posted by cventer

Peter dont hold out on us. This is allways a real challenge. Love to hear about how you went about the Ha blend.

It's complex..and not easily described on IIS.... but I'm giving it some serious thought and will probably do a write-up when I've got a bit more spare time.

BTW after an absence of a few days, I've uploaded the latest smaller (33%) but higher quality .jpg revision as the prior Las Vegas versions were probably a bit over the top

[alpal]

That's great detail Peter.
I had a go at adjusting it -
I hope you don't mind?
see here:
http://i262.photobucket.com/albums/i...arch2012_d.jpg