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lrgb percentage


iwols

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I usually decide how long I can image for - lets say 6 hours.

I will use about half the time on Lum binned 1x1 and the other half split equally between RG and B binned 2x2

If the target starts low to horizon but is climbing I take the RGB first so my Lum is taken at the highest/clearest point.

If its a descending target I take Lum first then RGB.

Not saying its the best way but it works for me !

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That sounds a good strategy Dave, I must admit I tend to do a sequence of twice as much Luminance as RGB just repeating itself, but using the higher altitude for the Luminance does sound a good plan.

Carole 

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5 hours ago, Skipper Billy said:

I usually decide how long I can image for - lets say 6 hours.

I will use about half the time on Lum binned 1x1 and the other half split equally between RG and B binned 2x2

If the target starts low to horizon but is climbing I take the RGB first so my Lum is taken at the highest/clearest point.

If its a descending target I take Lum first then RGB.

Not saying its the best way but it works for me !

why RG and B binned 2x2 thanks

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I believe this is because your luminance layer contains the important detail of the object and RGB is just adding the colour information and doesn’t need to have all the detail of the luminance.

i too am just learning the right balance with a mono camera. 

One thing to remember, if you do take the rgb 2x2 then don’t forget to take 2x2 flats! 

Bryan 

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I spend an evening on a filter. Current project, trying to get 3 hours each RGB and as much Lum as possible. Some cameras have a different QE response also. Like my ASI1600 is more receptive to red and green and a little less blue, but not by much. So you could say you'd need a little bit extra blue to match the others. I just shoot equal RGB. An hour each at least.

 

Regarding Carole's point above, if you bin RGB and you have Pixinsight, a star alignment will auto align the binned and non binned files without fuss.

zwo_asi1600mm-pro_qe_graph.jpg

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I don't like binning colour because I tend to use little or no luminance on the final stars, certainly on targets with starfields on 'empty' background. So I want nice tight stars with good colour close into the core rather than too saturated.

On the main question of the L to colour ratio, you'll probably find processing easier if you shoot the same amount per filter. However, if the target has interesting faint signal to bring out then shooting more luminance will do exactly that. You can shoot vastly more luminance to find the faintest stuff but combining it with the colour becomes considerably more difficult. Very strong Lum needs to be added in small interations, the colour saturation increased, the noise reduced and the partial lum re-applied, this process repeated several times. The last application of Lum is done without noise reduction to restore detail.

If imaging at high resolution it is worth allowing the seeing to inform your decision of what to shoot and when. If the FWHM values are good, shoot lum. If not, shoot colour. At lower resolution this is less critical.

Olly

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On 18/04/2019 at 12:14, ollypenrice said:

I don't like binning colour because I tend to use little or no luminance on the final stars, certainly on targets with starfields on 'empty' background. So I want nice tight stars with good colour close into the core rather than too saturated.

On the main question of the L to colour ratio, you'll probably find processing easier if you shoot the same amount per filter. However, if the target has interesting faint signal to bring out then shooting more luminance will do exactly that. You can shoot vastly more luminance to find the faintest stuff but combining it with the colour becomes considerably more difficult. Very strong Lum needs to be added in small interations, the colour saturation increased, the noise reduced and the partial lum re-applied, this process repeated several times. The last application of Lum is done without noise reduction to restore detail.

If imaging at high resolution it is worth allowing the seeing to inform your decision of what to shoot and when. If the FWHM values are good, shoot lum. If not, shoot colour. At lower resolution this is less critical.

Olly

If capturing RGB without binning, is it OK to use just the RGB without luminance?

In other words, what does the luminance add to the process, as the full spectrum of RGB has been captured with the highest resolution?

There's probably an obvious answer, but I'm only just beginning to learn how to use a mono camera.

Thanks

John

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Quote

If capturing RGB without binning, is it OK to use just the RGB without luminance?

Quote

your luminance layer contains the important detail of the object and RGB is just adding the colour

Quote

I don't like binning colour because I tend to use little or no luminance on the final stars, certainly on targets with starfields on 'empty' background. So I want nice tight stars with good colour close into the core rather than too saturated.

On the main question of the L to colour ratio, you'll probably find processing easier if you shoot the same amount per filter. However, if the target has interesting faint signal to bring out then shooting more luminance will do exactly that. You can shoot vastly more luminance to find the faintest stuff but combining it with the colour becomes considerably more difficult. Very strong Lum needs to be added in small interations, the colour saturation increased, the noise reduced and the partial lum re-applied, this process repeated several times. The last application of Lum is done without noise reduction to restore detail.

What you suggest Olly is great in an ideal world, but since here in the UK  we struggle with poor weather and some of us little access to darks skies, this is not always practical so we have to make the most of what little opportunities we get.

Carole 

 

Edited by carastro
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2 minutes ago, carastro said:

What you suggest Olly is great in an ideal world, but since here in the UK  we struggle with poor weather and some of us little access to darks skies, this is not always practical so we have to make the best of what little opportunities we get.

Carole 

May be OK for me though as I've recently emigrated to Malta, so hoping for plenty of clear skies soon.  Not had much opportunity to image yet as Malta's having one of the the worst springs in living memory with lots of windy cloudy days.  Four+ hours of astro-darkness in mid-summer to look forward to though. ?

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31 minutes ago, Starwiz said:

If capturing RGB without binning, is it OK to use just the RGB without luminance?

In other words, what does the luminance add to the process, as the full spectrum of RGB has been captured with the highest resolution?

There's probably an obvious answer, but I'm only just beginning to learn how to use a mono camera.

Thanks

John

You probably could just use RGB if you wish but it would be very slow indeed compared with using LRGB. Indeed the LRGB method was invented specifically to save time or get the best signal possible in limited time. (In professional imaging time is always limited.) The reason is simple: the L filter passes the full RGB spectrum simultaneously so you are capturing about 3x the signal per unit time as in any given colour filter. I added the word 'probably' because, in the case of very faint objects or parts of objects (galactic tidal tails, Integrated Flux etc etc) you may not be able to get the signal above the noise floor in anything but the L filter. There is no need for all the data to contain colour information so shooting some without it, at far higher signal to noise, makes excellent sense.

Theory might lead us to expect that 3 hours of RGB with the colour discarded would be roughly equivalent in signal to 1 hour of luminance. My own experiments find that it never is. An hour of luminance goes deeper than an hour per colour filter combined. I don't know why this is.

If you do shoot in RGB only, or try OSC imaging, you can still exploit a technique which is standard practice in LRGB processing: the processing objectives in RGB are entirely different from those in luminance processing. RGB is best processed for low noise (at the cost of both depth and resolution of detail) and intense colour. Luminance should be for processed for depth, resolution and low noise (which cannot be done unless you have collected a lot of signal which is where the L filter comes in...) In RGB-only or OSC processing you can make a synthetic luminance and process that as you might process a regular luminance, then add it a colour layer processed as described above.

At the risk of subjecting you to 'too much information,' lovely monochrome imaging :D offers still another option: on emission nebulae with overwhelming starfields you can make a gentle RGB layer with the smallest possible stars and then use that as a vehicle to carry Ha in red and OIII in green and blue. Done properly this can give you small, naturally coloured stars and vibrant, natrually coloured nebulosity. The problem with luminosity on such targets is that it tends to increase star size.

Olly

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46 minutes ago, ollypenrice said:

You probably could just use RGB if you wish but it would be very slow indeed compared with using LRGB. Indeed the LRGB method was invented specifically to save time or get the best signal possible in limited time. (In professional imaging time is always limited.) The reason is simple: the L filter passes the full RGB spectrum simultaneously so you are capturing about 3x the signal per unit time as in any given colour filter. I added the word 'probably' because, in the case of very faint objects or parts of objects (galactic tidal tails, Integrated Flux etc etc) you may not be able to get the signal above the noise floor in anything but the L filter. There is no need for all the data to contain colour information so shooting some without it, at far higher signal to noise, makes excellent sense.

Theory might lead us to expect that 3 hours of RGB with the colour discarded would be roughly equivalent in signal to 1 hour of luminance. My own experiments find that it never is. An hour of luminance goes deeper than an hour per colour filter combined. I don't know why this is.

If you do shoot in RGB only, or try OSC imaging, you can still exploit a technique which is standard practice in LRGB processing: the processing objectives in RGB are entirely different from those in luminance processing. RGB is best processed for low noise (at the cost of both depth and resolution of detail) and intense colour. Luminance should be for processed for depth, resolution and low noise (which cannot be done unless you have collected a lot of signal which is where the L filter comes in...) In RGB-only or OSC processing you can make a synthetic luminance and process that as you might process a regular luminance, then add it a colour layer processed as described above.

At the risk of subjecting you to 'too much information,' lovely monochrome imaging :D offers still another option: on emission nebulae with overwhelming starfields you can make a gentle RGB layer with the smallest possible stars and then use that as a vehicle to carry Ha in red and OIII in green and blue. Done properly this can give you small, naturally coloured stars and vibrant, natrually coloured nebulosity. The problem with luminosity on such targets is that it tends to increase star size.

Olly

Thanks for the info Olly, it makes more sense now.

John

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