Narrowband LRGB clarification & or advice please

[Ewan]

This is a long post i appologise.

Before i start i would like to say i have browsed a lot of help topics regarding these queries on SGL & other comparable websites, maybe i have just missed what i am after or i need it in really simple terms.

I had an all night imaging session last night, matchsticks in eye's kind of night ...but fun.

I decided to uninstall PHD then reinstall as i felt i had adjusted one to many items, lo & behold it seemed to work a lot better, i was managing 10 minute subs, i admit i think the stars could be marginally tighter.

I did 10 x 5 minute subs on M31 1st off to test guiding then slewed to NGC 7000, i am not sure what part i was imagaing as it's so large but i just wanted some data to post process on.

I captured 10 x 5 minute sub's & 6 x 10 minute sub's all in Ha 7nm, i also did 4 x 5 minute OIII & 10 x 3 minute sub's with the Red filter.

Now for my questions :-

1) Do i actually need to collect RGB to form any sort of coloured image ?

2) Can i just use the Red i collected & 'merge' with the Ha ? if so could someone post a link for a detailed tutorial ? (a lot of tutorials assume you know part of the process already which i don't).

3) I am sure i have read that i can just collect the narrowband information, Ha OIII & SII, & create a final shot with that data only ?

4) If so is the RGB mainly used for more depth, contrast & colour ie stars ?

I also have some Artemis queries very sorry.

1) In Artemis i use the FWHM to adjust for focus, i was doing a 10 second binned 2x sub for this & using a sub frame, i was getting the FWHM around 0.79-1.09, once the 10 minute Ha subs were taken & put into DSS the FWHM was averaging 3.34, does this sound good, fair or diabolical ?

As it's clear tonight i may well go out again especially as i had the Planostar flattener delivered today & it needs spacing, i may well save the spacing until another night though.

As usual thank you SGL & all it's members for making the astro journey a joyful if sleepless adventure

I have attached the stacked image just for some ney's or yay's on it's quality & content, oh can someone tell me what part of NGC 7000 i actually captured if it has a name that is ?

[Freddie]

Hi Ewan, you create the colour by assigning the different filters to be red, green and blue in PS. Obvious which is which with your R,G,B filters and there are different ways for your NB filters. The Hubble palette is often used. S to R, Ha to G, O to B. For NB, the true RGB can be added to give proper star colours. So you can create a colour image with anything, just depends what you want to do.

Your Artemis FWHM numbers are good, though 2xbinning may have an impact on the numbers (not sure though) If you get that with no binning that's a good number. Below 1 is VERY unusual for me.

[nmoushon]

1) Do i actually need to collect RGB to form any sort of coloured image ?

2) Can i just use the Red i collected & 'merge' with the Ha ? if so could someone post a link for a detailed tutorial ? (a lot of tutorials assume you know part of the process already which i don't).

3) I am sure i have read that i can just collect the narrowband information, Ha OIII & SII, & create a final shot with that data only ?

4) If so is the RGB mainly used for more depth, contrast & colour ie stars ?

1) You need to collect RGB if you are trying to achieve a natural looking color image.

2) My understanding is the Ha is its own layer. You don't combine it with your R. So you can take a HaRGB just like you would take a LRGB. Or can go farther and do HaLRGB. Could be wrong but thats my understanding.

3) Correct. Its commonly called the Hubble pallet.

4) RGB is used to get a natural star color look to add to the narrowband image. (i.e. Hubble pallet) You do not add RGB to your Ha OIII & SII sets. Unless for star color. But that is a seperate process that involves layers and masks and two sets of combined datea. If you want to add depth to your image take longer subs and more of them. If you want contrast you need to take more subs to be able to play with the data more to pull out the contrast and not the noise.

[Freddie]

Ha and R are often blended. All sorts of ways of doing it but merging two layers, adjusting opacity and then flattening is a simple way.

[Ewan]

Thank you both so far, i think once i get the basics down ill be ok ( bit like the rgb planetary help you gave me Freddie)

So just with the data i have so far, Ha, OIII & Red can i make that into a colour shot for now just to geg the post processing understanding started ?

I will look for an idiots guide for the processing side of things then.

I thought the FWHM looked good Freddie, the reason my stars may look a little odd is maybe from dew as the setup was drippng when i finished. The outter edge stars need flattening but i think guiding was pretty good this time round.

Lesson learned on fiddling with things as phd really very nearly is push here dummy.

Looks like sporadic thin cloud but very small, hoping it blows away though.

[ollypenrice]

Don't bin for focusing. I'd advise 3 to 4 second subs in Bin1. You'll get an artificially low number when binning and less accuracy.

I don't agree with nmoushon's point 2. If you simply apply Ha as luminance to RGB you'll get an awful mess with reds washed out to pink and huge blue star haloes. For a simple but serious way of combining Ha with an RGB or LRGB image, try this;

Align the Ha to the (L)RGB image.

Split the (L)RGB into its channels.

Select and copy (Ctrl A Ctrl C) the Ha and paste it (Ctrl V) onto the red channel.

In Layers, change the blend mode from Normal to Lighten in the drop down menu.

Use the eyeball in Layers to see what the Ha is dong to the red. If it isn't doing much, open Curves and lift the Curve in the top Ha layer to bring it into play.

Flatten (Ctrl E)

If you have 0111 as well you can use this method to add a little in the same way to both green and bue. Don't go mad!

In Channels merge the channels, following the prompts, so choose RGB mode and then put red in the top channel, then green, then blue in the dropdown.

You can also boost Ha signal in any RGB image by going into Image, Adjust, Selective Colour and when it opens the reds by default just move the top slider to the left. This is remarkable, trust me!

Typical RGB with Ha to red and O111 to G and B looks like this:  http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-L2tvm8J/0/X3/BEST%20CLAW%20WEB-X3.jpg

I don't do Hubble Palette or false colour of any kind so I can't help there.

Olly

[Freddie]

Put your R in place of the S II. Will look a bit odd but will give you something to have a go with.

[nmoushon]

I'd disregard what i said in #2 and go with Olly. He's got a bit more experience than me  I thought what a said was a bit off but part of me was saying it was right. My brain must have got it mixed up with somehting else. I did have a disclaimer there though lol but my bad on the not so right info there.

[Ewan]

Thanks Olly, Freddie.

Don't bin for focusing. I'd advise 3 to 4 second subs in Bin1. You'll get an artificially low number when binning and less accuracy.

I don't agree with nmoushon's point 2. If you simply apply Ha as luminance to RGB you'll get an awful mess with reds washed out to pink and huge blue star haloes. For a simple but serious way of combining Ha with an RGB or LRGB image, try this;

Align the Ha to the (L)RGB image.

Split the (L)RGB into its channels.

Select and copy (Ctrl A Ctrl C) the Ha and paste it (Ctrl V) onto the red channel.

In Layers, change the blend mode from Normal to Lighten in the drop down menu.

Use the eyeball in Layers to see what the Ha is dong to the red. If it isn't doing much, open Curves and lift the Curve in the top Ha layer to bring it into play.

Flatten (Ctrl E)

If you have 0111 as well you can use this method to add a little in the same way to both green and bue. Don't go mad!

In Channels merge the channels, following the prompts, so choose RGB mode and then put red in the top channel, then green, then blue in the dropdown.

You can also boost Ha signal in any RGB image by going into Image, Adjust, Selective Colour and when it opens the reds by default just move the top slider to the left. This is remarkable, trust me!

Typical RGB with Ha to red and O111 to G and B looks like this: http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-L2tvm8J/0/X3/BEST%20CLAW%20WEB-X3.jpg

I don't do Hubble Palette or false colour of any kind so I can't help there.

Olly

I'll give that a try Olly when i get the L G & B data, i only went for Red last night as for some reason i assciciated it with Ha, my mistake, just glad i got what i did 1st time round.

Agreed about the Selective Colour, something i had a trial with when i was doing planetary just to adjust a few things.

I did give up using binning on the focussing Olly, as soon as i saw the enlarged pixels i thought 'that cant be as good as a small pinpoint lightsource', i did find myself keep trying to get the stars tighter & tighter, then oops start again but it is a very good way to get focus i thought. I ended up doing 10 sec loops on 1x as i progressed with the learning curve & the figures were from 0.89 - 1.25 sometimes a little higher but in the end i just settled for it & got shooting.

Put your R in place of the S II. Will look a bit odd but will give you something to have a go with.

I follow Freddie, as i have the Oiii & Ha i can do a substitute as it were.

So am i correct in thinking that Ha,OIII & SII are the same thing , to an extent, as RGB but a lot narrower ?

Really please with this setup now & the Atik is a godsend, stunning tech tbh, ran happily at -18.1 all last night so i didn't feel Darks were needed either.

Ok well i think i have enough to go on for now & i will be doing some more reading on post processing as the clouds have joined me again.

[Freddie]

Hi Ewan, SII, Ha and OIII are not related to RGB but just mapped to those colours to give the Hubble palette. They can be mapped in any way as for NB the colours are false so anything goes. In fact as described above Ha is more related to R but in the Hubble is mapped to G. If you have "making every photon count" there is a nice section in there (pg30-32) showing the same images with different colour mappings.

[nmoushon]

So basically Ha is typical mapped to G, as stated above, for hubble pallet. But you could map it to R or B also to switch up the colors.