LRGB Manual Alignment & Merging

[groberts]

Can someone point me towards a simple (I hope!) processing tutorial, preferably video but text is also OK, that shows how to manually align the merge LRGB channels in PS. 

Thanks, Graham

  

[Tim]

I might be wrong but I don't think PS has an easy function for registering one image against another and then altering the geometry of the image to match your reference image, so you will need to use another program to sort out the alignment. Normally you would align your colour RGB data sets to your stacked Luminance master file.

Once that is done there are a couple of ways to assign the mono RGB masters to the appropriate RGB channels in PS. I'll see if I can find a video.

[Tim]

Does this one help you?

 

[groberts]

Thanks I'll take a look. 

I already have the stacked and registered LRGB images taken as a sequence at the same time + tracking and guiding, which I normally merge using the Channels in PS. However, on this occasion the final image below (something of an experiment), looks to me like the red channel is not aligned - hence my thought that perhaps I could align the channels manually?

Graham

       

[Freddie]

How do you normally align the individual stacks?

[carastro]

This is the method I always use but you have to register your stacked images first.  I do that in Registar.

http://www.eprisephoto.com/videofiles/h1b3af346#h1b3af346

I do apologise there seems to be an issue with running the video, I think she mentions some people are having problems with videos on her site but if you can get past it its a good tutorial.   I managed to get it to work after fiddling with it. 

Carole 

[groberts]

Thanks Carole, looks like there's some good stuff there, will take a look.

Graham

[carastro]

Basically, you need to register the images so that they sit accurately on top of each other, make a duplicate of one of them and call it say RGB, then convert this into RGB as its currently mono (Image/Mode RGB), and then go into channels.

Paste Red into the Red channel

Green into Green channel 

Blue into Blue channel

Click on the RGB at the top of channels and hey presto you have a coloured image.

If the various channels are slightly mis-aligned you can slide them around using to move tool but this will only work if the filters are registered to each other first. 

Carole 

[Freddie]

It's odd that whatever you are using to stack hasn't aligned the individual stacks properly. I assume you have done that?

[groberts]

1 hour ago, carastro said:

If the various channels are slightly mis-aligned you can slide them around using to move tool but this will only work if the filters are registered to each other first. 

Thanks Carole.

As you say, I'm having problems running some of the videos. Notwithstanding, I'm OK with registering + stacking in DSS + combining through RGB channels in PS, which most of the time come out fine. It's the last part that interests me, can you expand on how to do this + at what stage e.g. is in in the compiled RGB image?

Graham

  

[groberts]

8 minutes ago, Freddie said:

It's odd that whatever you are using to stack hasn't aligned the individual stacks properly. I assume you have done that?

Yes - see above.  It's just this particular image that's gone awry and to me the red channel looks to be the problem?  

[carastro]

Are you on TViewer, or where abouts in Surrey are you, I am in Bromley, might be easier to show you.

Carole 

[Freddie]

Do you align the r g and b files after or during stacking in DSS?

[carastro]

After  stacking in DSS, if you put them all in DSS it will stack them all as one file and you'll end up with a mono image.

Carole 

[groberts]

3 minutes ago, carastro said:

Are you on TViewer, or where abouts in Surrey are you, I am in Bromley, might be easier to show you.

Thanks for the offer Carole but no.

3 minutes ago, Freddie said:

Do you align the r g and b files after or during stacking in DSS?

I register then stack in DSS and it's always been OK, not aware of any specific Align action, or am I missing something? Once I have three RGB images I paste into respective PS channels.  

[carastro]

If you're using photoshop, open the channels tab and click on the colour that is misaligned, but make sure you have all the colours switched on at the same time, then use the "move tool" top left of the tool bar in PS then simply put your cursor onto the image and move it it will move that colour only.  

tip: Zoom in so you can see accurately what you are doing, and when the colours are aligned you are done.

The biggest problem is if the stars are of different sizes.

Ideally try to shrink the stars on the filter that are too large.  

There are some more complicated ways to deal with star sizes, but try this in the first instance.

Carole 

[groberts]

Thanks Carole that's very helpful, I'l give it a try this afternoon.

[carastro]

I just tried to align the stars in your crop above, but it was quite difficult as there are some very different shapes to the stars in the different filters, particularly in the blue.  Might be worth taking another look at the stacks there could be some rogue images in there. 

Plus I wonder how good the registration is as I could get them to "sort of" line up in one place but not so well in another.

Carole 

[Freddie]

53 minutes ago, carastro said:

After  stacking in DSS, if you put them all in DSS it will stack them all as one file and you'll end up with a mono image.

Carole 

If you don't align the individual R,G and B stacks during the stacking process they can be aligned in DSS after. This does not refer to stacking the individual subs this refers to aligning the individual R, G and B stacked files. You are referring to stacking, I and talking about aligning. 

[Freddie]

1 hour ago, groberts said:

Thanks for the offer Carole but no.

I register then stack in DSS and it's always been OK, not aware of any specific Align action, or am I missing something? Once I have three RGB images I paste into respective PS channels.  

You are missing something !! As well as stacking the individual subs to produce the R G and B files you also need to ensure this R G and B files are aligned. Aligning and stacking are two different things.

Easiest way is to align during the stacking process. This done as follows:-

Load your R subs as normal but then right click on an individual sub in the list and select "use as reference" Then stack as normal.

When you load the G subs also load the R sub you selected as the reference frame. Find it in the sub list and again right click and select "use as reference" now make sure that sub is not ticked to ensure it is not included when the G subs are stacked.

Now load the B subs and repeat as above.

You will now find that the three R G B files are aligned so when you put them into PS there will be no need for manual adjustment. This method should always be used to ensure your files are aligned properly.

You may however find some slight misalignment if as Carole says you have some different star shapes. Registar (as Carole has referred to) is better at aligning but is not free like DSS.

Hope that helps as I think there has been some confusion over stacking and aligning.

 

[groberts]

Many thanks Freddie, I think I am doing most if not all of what you outline.  My workflow is:

1. Load all subs;
2. Run to Register all subs once;
3. Select the sub with the highest score, whether its RRGBHa or OIII and choose that as the reference frame;
4. Re-register again, now with reference to the aforesaid 'best score' frame;
5. Stack respective wavelengths to produce pre-processed stacked images;
6. Thereafter I take each stacked image stack, stretch + all the other usual Photoshop stuff and combine using the channels.

Hope that's correct? I presume that through the registration process all the subs are now aligned, using the reference frame as the point of teferecne for alignment before stacking.   

Graham 

     

[Freddie]

I haven't used DSS in years (I use AA6) so I'm not sure exactly what registering does. Does it actually align all the frames?

The key of my method is that the same reference frame is used for each stack so when you save the stacked R, G, B etc files the stars are all aligned to the same reference frame in each of the files so the R G B etc files will all be aligned. 

I guess to be sure both methods produce the same results you could compare my method to what you do.

The other thing you could try if you are still getting slight misalignment after stacking and combining in PS is to load the combined RGB file from PS into Registax and do an RGB align in there.

[carastro]

Quote

When you load the G subs also load the R sub you selected as the reference frame. Find it in the sub list and again right click and select "use as reference" now make sure that sub is not ticked to ensure it is not included when the G subs are stacked.

That's interesting information Freddie I did not know you could do that in DSS, not that I have used DSS for mono imaging stacking since I first started and then soon changed to Astroart.  

Carole 

[Freddie]

Yes, it was the way I aligned R, G, B, Ha etc etc before I too moved to AA.  Have you seen there is now SP4 available for AA?

[groberts]

OK thanks Freddie I think we're doing the same thing and the registering ensures that all the subs are indeed aligned with reference to one master sub i.e. the best one.