My version of Eta Carina

[Tom Davis (Tom)]

I've never really done any narrowband stuff, but since putting a scope in South Australia I've ad to use every clear night. So since the moon gets in the way during a portion of the month I'v tried some NB imaging. Processing this stuff is challenging.

Here is my version of your Eta Carina nebula. It is in the Hubble palette. Man, I'd love to see this baby through binoculars!

http://www.tvdavisastropics.com/astr...s-1_000072.htm

I hope you enjoy. It does look different in this palette but the detail is quite amazing.

Tom

[renormalised (Carl)]

Just blew everyone else's shot away there, Tom. That is an exquisite image!!!. Well done

[strongmanmike (Michael)]

I think I already commented on this image elsewhere..? But it's worth another comment - Bluudy Marvelous mate!

I just posted a couple of crops of Eta in Halpha myself, love to see the same bits cropped from your image so they'd be in colour (all be they funny colours )

Mike

[strongmanmike (Michael)]

Actually Tom, can you describe how you add the RGB data to just the stars without affecting the rest of the image?

Mike

[Tom Davis (Tom)]

Originally Posted by strongmanmike

Actually Tom, can you describe how you add the RGB data to just the stars without affecting the rest of the image?

Mike

After assembling your S-H-O and R-G-B images, align then with your favorite program (use Registar for this because I want them to be exact).

In PS open the SHO and with the Select>color range tool select the magenta halos which surround the stars (this is inherent to the SHO combine). Select>Modify>expand by one pixel. Feather by 1 pixel. In Image>adjustments>color balance move the slider away from magenta towards green until most the the magenta is gone. Deselect.

Now use the color range tool to select just the stars. Modify>expand by 1-2 pixels. Feather by 1 pixel. Go to Select>Save selection and name it something like "stars".

Open aligned RGB image. Select>Load selection "stars". Now your exact star selection is mapped into your RGB image. Cntrl-C to copy the selection.

Go back to your SHO image and Cntrl-V to paste the RGB stars exactly onto the SHO stars! Here's where you have to play with it a bit. Change the blend mode from normal to lighten or color. Sometimes one looks better than the other. Flatten.

Now your RGB stars have replaced your funny looking SHO stars. Let me know if this is not clear

Cheers,
Tom

[Hagar (Doug)]

Although not a real fan of false colour this is a stunning image with so much detail.
Lovely detailed image Tom

[Garyh]

Tom! I love it! You have done a beaut job with this!

[strongmanmike (Michael)]

Originally Posted by Tom Davis

Now use the color range tool to select just the stars.

How do you do this bit exactly..?

Thanks heaps Tom, I'll give it a go. I have just recieved a set of Astronomiks HaOIIISIIHbeta so this was the thing that was outside of my current processing skills

Mike

[atalas]

Great work Tom!

[gregbradley]

Lovely fine detailed image. Thanks for the stars tutorial. Funny as I was just watching an educational DVD on how to select out the stars separately. Wodaski's book goes over a method to do this but I did not find it to work very well.

Whilst there appears to be no right or wrong in narrowband I have found in my dabblings with it and from advice from others (notably Richard Crisp who has done a lot of work in narrowband) that the red channel - S11 is where it gets hard and breaking the Ha dominance in the image is key.

My first efforts with Eta C in narrowband came out similarly with blue and green being dominant. I think this is common with most narrowband imaging. Fred could comment here.

So you have some choices:

1. Expose much more of S11 and use 2x2 binning.
2. When doing RGB combine work out various combine ratios pumping up the S11 and O111 as Ha will almost always be very dominant and overwhelm the image.
3. In the final image using Ha as a luminance layer will also add some sparkle and detail to the image.

I found I had to push the red channel with curves to bring it up and the blue/green dominance became more balanced and overall a more "traditional" Hubble narrowband look.

So one formula is:

1. Image Ha 1x1 but O111 and S11 in 2x2.
2. Use much longer subs for O111 and S11 (20-30 minutes or even longer) to get the signal to noise ratio up. Use longer total exposure times for these as well with S11 getting the most.
3. When doing your SHO combine weight S11 the highest, then O111 the next highest and Ha leave at 1.
4. Be prepared to push the red channel harder with curves to break the blue/green dominance in some images.
5. Taking shorter RGB image for the stars and installing as you have detailed in your excellent tutorial.

Another formula I personally like is:

1. Do an LRGB image.
2. Take O111 and Ha and add to the image.
3. I usually don't bother with S11 as it adds little to the final image.

So HaO111LRGB can make a very interesting image on some objects like Vela and appears to be more of a tradiitonal LRGB but with extra details enhanced. Don Goldman has done some great work in this format.

I hope this helps and I don't consider myself an expert on narrowband nor like it that much but this is what I have learnt so far.

There are some stunning narrowband images around. Ken Crawford has done a marvellous NGC3576 for example. That object looks better in narrowband than LRGB. But it also requires a largish image scale.

Greg.

[Tom Davis (Tom)]

Originally Posted by strongmanmike

How do you do this bit exactly..?

Mike

Open your image in PS, then go to Select>color range tool. Move the slider almost all the way to the left. Then use the eye dropper and click on various stars in your image. I start with the brightest then move to the next dimmest and so forth. In the color range window you will see the stars appear. After you get a fair number selected move the slider slowly to the right. This will bring more stars in. Do not move so far as to select any of the nebula. When you have all the stars you want click ok.

Just play with it.

Tom

[gregbradley]

Hi Tom,

Do you make a separate star layer like this in all your images so you can process the stars separately from the main image?

How do you do your colour balance?

You often achieve a unique and very aesthetic colour balance in your images.

Greg.

[Tom Davis (Tom)]

Originally Posted by gregbradley

Whilst there appears to be no right or wrong in narrowband I have found in my dabblings with it and from advice from others (notably Richard Crisp who has done a lot of work in narrowband) that the red channel - S11 is where it gets hard and breaking the Ha dominance in the image is key.


I found I had to push the red channel with curves to bring it up and the blue/green dominance became more balanced and overall a more "traditional" Hubble narrowband look.

Greg.

Yes, since there is no G2V calibration for NB images it is much more of an art form than LRGB. My blend weights for this image was SII 5, Ha 1, OIII 7.

Tom

[gregbradley]

Originally Posted by Tom Davis

Yes, since there is no G2V calibration for NB images it is much more of an art form than LRGB. My blend weights for this image was SII 5, Ha 1, OIII 7.

Tom

What about in LRGB imaging?

Your blend weights seem similar to what I have used as well. Even with that I think the red channel needed to be pushed hard.

Here is an example of what I mean about S11 being dim.

Recently I imaged the Horsehead and swapped what I thought was the Ha filter from my Apogee U16M to my FLI ML8300 and filter wheel.

It was in fact the S11 Astrodon 5nm not the Ha.

I took 10 and 15 min subs and was disappointed why the "Ha" was so dim and noisy.

I went to 2x2 binning and ended up doing 7 hours 15 minutes for an overall disappointing and still dim and noisy result. I only discovered a few weeks later it was the S11 filter and then reimaged Horsehead with the Astrodon 5nm Ha.

The links below show the 2 results:

Ha 1 hour 50 mins 1x1 binning

http://upload.pbase.com/gregbradley/...09682619/large

S11 7 hours and 15 minutes mostly 2x2 (some 1x1)

http://upload.pbase.com/gregbradley/image/109682983

Are you doing your SHO combine by assigning each to a channel in Photoshop rather than an RGB combine in Maxim or CCDstack? I found it worked better using the former and more control and using curves to get the combine to suit.

Cheers,

Greg.

Greg.

[Tom Davis (Tom)]

Originally Posted by gregbradley

What about in LRGB imaging?

Are you doing your SHO combine by assigning each to a channel in Photoshop rather than an RGB combine in Maxim or CCDstack? I found it worked better using the former and more control and using curves to get the combine to suit.

Cheers,

Greg.

Greg.

In LRGB my color combine weights are based on G2V calibration.

I do all color combine (RGB, SHO, HOO) in Maxim. I then adjust in PS for histogram balance.

Tom

[gregbradley]

Thanks Tom.

I appreciate the tips.

Greg.

[Quark (Trevor)]

Hi Tom,

What an outstanding image, such delicate detail, incedibly well done.

Tom, your the man.

Regards
Trevor

[Tilt (Michael)]

So... much... data.

Superb image

Michael

[Tom Davis (Tom)]

Thanks everyone for the kind comments.

Tom

[multiweb (Marc)]

that looks unbelievable Tom. Top work. Thanks for the masking tips on keeping star colors. Very instructive.