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Refined Rosette

ollypenrice

By ollypenrice
in Imaging - Deep Sky

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ollypenrice

ollypenrice

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I did this as an HaRGB nearly a year ago. I didn't shoot any Lum, partly to see what it would be like without. The background was a bit stark with too hard a cutoff between the background sky and the nebula, I thought, so I had a short burst of L on it last night, both Taks catching three hours and the TEC adding a couple of hours on the middle part at longer focal length. The end result isn't vastly different but the trasititions around the edge of the nebula are indeed a bit gentler. The stars have inevitably grown a bit, though.

Happy Christmas to all.

Olly

ROSETTE%20HaLRGB%2016%20Hrs-X3.jpg

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Tom OD

Tom OD

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Super stuff Olly, and the background stars are not that noticeable at all. That region is in the Milky Way so I was expecting a lot more of them really. Beautifully controlled.

I reckon you could push a little more contrast out of the central pink areas to separate the "thorns" more from the background. A little Micro Contrast curve maybe?

Tom.

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ollypenrice

ollypenrice

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29 minutes ago, PhotoGav said:

That's a lovely pink rose!

Your stars are always a wonderful selection of colours... please tell me your secret mix of herbs and spices - what are the RGB sub details for this one?!

I'm not really aware of doing anything particularly remarkable to my stars. I shoot the colour in 10 minute subs, usually, rather than longer. This stops the cores blowing out too much, but they do hit 65000 counts inevitably. On the slower TEC I may go to 15 minutes. It depends on how many stars, how bright, and whether or not there is faint colour data to chase. If so, I'll go for 15 mins rather than 10.

I shoot equal amounts per colour and combine them at parity, which is nearly right. When I run the RGB through PI's DBE the final colour adjustment is made by the alogorithm. (So far, no skill!)

My RGB is almost always given a simple log stretch - by moving the grey point slider to the left. I don't mask stars in the RGB. (Still no skill!)

I run Noel Carboni's Increase Star Colour and thank him from the bottom of my heart, but he does pull my stellar blues a bit too far into the cyan, so I put them back with a lift in magenta applied just to the stars. (A bit of skill, mostly Noel's!!)

I use the two well known colour enhancement tricks of 1) increasig the contrast in a and b channels when the image is in Lab colour mode and 2) creating three layers, the top set to soft light, then flattened, the blend mode changed to colour and flattened. If this has pulled the star colour about, again I select the stars and use Selective Colour to put them back to their original colour. (Very low skill level! Just have the original RGB on one screen - I use two screens - as a reference.)

That's it for the RGB. The thing is not to dump vast luminance stars on top of them, so I do usually mask the L stars when stretching.

I have two advantages, a very dark site needing no LP filtration and a much maligned set of Kodak cameras with fabulous well depth. This does help on stars, I think.

Olly

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swag72

swag72

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7 minutes ago, PhotoGav said:

Olly, you are a gentleman to share such details, thank you. I think my first mistake is that I don't shoot long enough RGB subs. Experiments will follow. Thank you for your help.

Interesting ....... I have recently had a little go at RGB........ and I've done 300s subs. I have THE most massive halos in the blue, so I'll be shooting some shorter subs to try to avoid them and somehow bludgeon the shorter subs in to cover the halos.... that's the theory anyway. I've given it no thought or experiment as yet! 

I could be well off the mark, I don't do enough RGB to know :)

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PhotoGav

PhotoGav

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1 hour ago, swag72 said:

Interesting ....... I have recently had a little go at RGB........ and I've done 300s subs. I have THE most massive halos in the blue, so I'll be shooting some shorter subs to try to avoid them and somehow bludgeon the shorter subs in to cover the halos.... that's the theory anyway. I've given it no thought or experiment as yet! 

I could be well off the mark, I don't do enough RGB to know :)

Interesting indeed... 300s is what I have been doing at around f5 and am suspicious that it is just too short to really capture rich colour. I will be upping the subs to 600s with the next project and will see how that changes things.

As for halos in the blue channel - yup, that sounds familiar! Only the really bright stars are affected. What target have you been on Sara?

Apologies to Olly for taking this thread off on a slight tangent, but hopefully it is a useful one. If not, we can always start a new thread elsewhere...

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swag72

swag72

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A few years ago I found something that recommended how much RGB was needed when compared to Luminance to get good colour. 

I can't find it at all now, but I do remember that it said that if you wanted a 'rich' colour then you had the same amount of RGB as luminance data. I wish I could find it now :(

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ollypenrice

ollypenrice

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33 minutes ago, swag72 said:

A few years ago I found something that recommended how much RGB was needed when compared to Luminance to get good colour. 

I can't find it at all now, but I do remember that it said that if you wanted a 'rich' colour then you had the same amount of RGB as luminance data. I wish I could find it now :(

It's much easier to process LRGB if you have the same amount for each of your four channels. Easier, that is, to go fairly deep with good overall colour saturation. However, if you are chasing the faint stuff then you'll want lots of luminance and then it tends to wash out your colour. Following Rob Gendler, R Jay GaBany and others, what I then do is add the L iteratively to the RGB at low percentages. With each partial iteration of L you can boost the saturation of the lower RGB layer, add a slight blur to the top L layer to keep down the noise, flatten and repeat. Each time you add a tad more L. On the final application of L you don't blur it, of course, since you want all the L sharpness.

Increasingly I stop short of pushing the L as far as it will go in processing. I take it to maybe 70% of a manic stretch and then do the manic bit to the LRGB together.

Olly

PS I first started paying serious attention to star colour thanks to Peter Shah, who showed what was possible. It set his images apart, giving a varied colour context across the frame. I think Paddy is making a similar point. I regard Peter as the master of star colour.

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Tom OD

Tom OD

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I m a fan of the Peter Shah stars too. He mentioned that just make sure you don't clip them with the histogram :)

I tend to run the histo tool in PI up to the point of the white clipping, so I m watching the white clipping % carefully.

I selectively boost the saturation on the red /yellow / golden stars a bit, and maybe a little on the blue separately after using the colour range tool to select them

When layer Lum on top, I generally have the lum stars masked or shrank with the Morph tool in PI or min in PS.

I suppose you could go back and re layer jus the RGB stars back in after the lm has been applied globally.    

 

 

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Petergoodhew

Petergoodhew

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I'm just starting out on adding RGB stars to narrowband images, and seeking guidance from those more experienced.  For imaging the stars I'm proposing 300s subs at F7, but am wondering how many subs I need to shoot for decent colour given that I'm only using the stars and not any nebulosity?

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ollypenrice

ollypenrice

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On 25/12/2016 at 22:28, Petergoodhew said:

I'm just starting out on adding RGB stars to narrowband images, and seeking guidance from those more experienced.  For imaging the stars I'm proposing 300s subs at F7, but am wondering how many subs I need to shoot for decent colour given that I'm only using the stars and not any nebulosity?

Very little, I'd say, Peter. Maybe even the less the better since you want to hold the colour into the stellar cores. However, I only think RGB stars are appropriate in NB images simulating RGB. (That's usually Ha-OIII-OIII. I wouldn't put RGB stars into a Hubbe platee image, for instance.)

Olly

Edit, Although 'platee' is a nice word and deserves to exist I think 'palette' might have been more precise...

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