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HaRGB Imaging - Sub Lengths... Help Please!


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So, I am slowly clambering up the mono CCD learning mountain and really enjoying the results so far. My next project is to be The Elephant's Trunk, which I intend to shoot in HaRGB, but I am not confident that I know what subs and lengths I should go for. I will be using the ED80 with a reducer and the QSI683. Would the following recipe be the most effective?

6 x 1200s Ha

3 x 1200s R

3 x 1200s G

3 x 1200s B

All at 1x1 binning

As for processing, should I use the Ha as the Luminance and perhaps mix some Ha with the R?

Do I not need to shoot any L at all?

What about shorter binned RGB data? Would that be better?

Please share your experience and knowledge with me and help me to avoid some clangers!

Thank you.

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If i was to do an HaRGB then i would process the RGB image and then apply the Ha in PS as lighten red in layers to a level that looked good. But you can use it as a LUM layer but you need to watch the blue rings around the stars as the Ha stars will be smaller.

The best thing is to play around as there is a lot of options and more than one will work for a pretty picture.

Here is an image of mine that is only HA, green and blue, no red was taken.

NGC6559 and surroundings L(HA)RGB

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Personally my recipe would be something like 1800s in Ha and get about 7-8 hours of that in total. Then I'd be looking at much shorter RGB subs, otherwise you are going to burn out the cores of the stars - My last RGB runs were about 120s each, and 50 or so of them - All 1x1 bin for me!

As said above, you can skip the green if you are short on time and use a synthetic green channel. In fact, I often skip the green channel on the few occasions I do RGB imaging.

I'd be adding the Ha to the red as you say and also using the Ha as a luminance layer.

Well, that's how I'd start to plan it anyway!!

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Thank you Raymond & Sara, though the horse has bolted... I collected a set of subs for this target last night. Fingers crossed that they make some kind of a pic. In the end I got 8 x 1200s Ha and 6 x 600s of RGB each. Pic to follow at some point!

Raymond, just had a look at your Flickr page, wow, some fabulous images there and that is a mighty scope!

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Im going to revist some HaRGB soon, lsat time i tried i Binned the colour and it did not at all help with star size which i prefer from the Ha data.

Not sure on what target though yet, I need to find something to sink the subs into while im waiting for Orion.

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Don't bin the the colour unless you are going to tidy the stars up again with Lum and even then I woudn't advise it. Ha gives small stars, L gives big ones and RGB gives something in between in the kind of real world sub lengths you're likely to use. Binned stars are horrible big bricks unless you are working at a long focal length. They sit very badly with Ha data and its tiny stars. To be avoided.

I agree with Sara. Long Ha and shorter RGB. I've done this in HaLRGB and HaRGB. I rather prefer the HaRGB. But they have different looks.

As RAC suggested, Ha into red in blend mode lighten is the most honest way because Ha is red. A little applied as Lum will be very tempting but more than a little will be 'pink with bue halo' territory.

Enjoy the project.

Olly

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Thank you Olly. I have the subs and will now give the processing a try... Fingers crossed!

Earl, there's plenty up there, the tricky thing is picking where to concentrate the efforts. Look forward to seeing the results wherever that may be. Good luck!

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