12 replies to this topic

[poolemarkw]

I'd like to combine images taken with the Optolong L-Extreme filter with images taken with the Optolong L-Pro filter.   The goal is to capture the Ha and Oiii data, which restricts the star colors, and combine it with L-Pro data that DOES capture the star colors.    I'd like to know if these get stacked together (I use Deep Sky Stacker) or do they get stacked separately, then combined in some way.   I only use PhotoShop for post processing.   Please let me know how you do this, or if there are any youtube videos our other websites that relate how to best do this.

 

Thanks!

 

Mark

[DirtyRod]

Stacked separately and then combined in post. You have to use the same reference frame in DSS in order to ensure both are oriented correctly. 

[poolemarkw]

Thanks DirtyRod.   That makes sense.   Does each image get fully processed in PhotoShop and then combined, or do they get combined in PhotoShop and then processed?

 

Mark

[drd715]

There are a couple of programs that can be used to separate the stars from the main subject (nebulae) .  Then the stars and nebulae can be processed separately to retain star color, Then recombined.  Sometimes you can take your images both in a longer exposure and a shorter exposure then separate the stars from the short exposure and recombine with the nebulae images from the longer exposures. The  shorter exposures of the stars will tend to not saturate the pixels and should retain the correct star colors.

[BucketDave]

The idea is that you take images with each particular set-up and then stack. You also to gradient reduction etc at this stage. Save the stacked image and repeat for images from other set-ups.

Now bring the stacked images back into DSS (or siril, PI, APP etc) and register them as a group. Save them.

You can now remove stars etc. because the image files contain the registration data on their stars (even if the stars in the image have been wiped).

Finally, bring them back into your program and add together.

This took me ages to figure out because i didn't realise that images have to be registered together in order to overlay one on another. I thought they just had to be the same size. D'oh!

[poolemarkw]

Hi BucketDave,

 

I was with you until you got to step 3:

 

- Step 1 is stacking the L-Extreme files (lights, darks, flats, dark flats).   I'll save that stack as L_Extreme.tif

- Step 2 is stacking the L-Pro files (lights, darks, flats, dark flats).  I'll save that stack as L-Pro.tif

- Step 3 is registering and stacking the L-Extreme.tif and L-Pro.tif files, or just registering?

- Step 4?

- Step 5?

 

Thanks,

 

Mark

[DirtyRod]

Thanks DirtyRod.   That makes sense.   Does each image get fully processed in PhotoShop and then combined, or do they get combined in PhotoShop and then processed?

 

Mark

Depends. On this M31 in my gallery, I did a complete processing of each and then brought in the Ha I wanted. On the M42 I'm working on now, I'm integrating a separate stack for the core so I did a partial processing of each image before combining. I stretched them both and got the colors pretty close before blending the core of the 15 second stack into the stack with 60 second subs. After blending I will finish processing the combined image. 

 

Lots of different ways to skin this cat but I do not bring them back into DSS after stacking each one. I go directly into Gimp. I remove the stars on the broadband image using Starnet and will only use those stars to get better colors.

Edited by DirtyRod, 28 November 2022 - 03:24 PM.

[Psyire]

I did this recently but I use PixInsight so my exact process was a bit different.

 

The theory is the same though.  I stacked both sets separately and then just used the RGB stars for my HOO palette image.  I also then did an HaRGB image using both sets of data.

 

As others have already said, the key is to register them to the same image.  If you forget this step you can align in PixInsight using Staralign process.  I think there are also a few other methods floating around out there.

 

 

You can see the result of both images here: https://elusivephoto...hant_Trunk.html

[poolemarkw]

Thanks everyone for your replies.   A related question is:  Can you simply stack the two resulting stacks to obtain both reflection and emission data and more star color?  For example, I took the picture below using just the L-Extreme filter.   What is obviously missing is the blue reflection data.   Would this work?

 

- Stack the L-Extreme lights, darks, flats, flat darks - Save as L-Extreme.tif

- Stack the L-Pro lights, darks, flats, flat darks using the same reference frame as used for the L-Extreme data - Save as L-Pro.tif

- Stack these two stacks

 

Wouldn't this accomplish the goal of getting more detailed emission data, capture the reflection data, and add color to the stars?

 

Thanks,

 

Mark

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[DirtyRod]

Thanks everyone for your replies.   A related question is:  Can you simply stack the two resulting stacks to obtain both reflection and emission data and more star color?  For example, I took the picture below using just the L-Extreme filter.   What is obviously missing is the blue reflection data.   Would this work?

 

- Stack the L-Extreme lights, darks, flats, flat darks - Save as L-Extreme.tif

- Stack the L-Pro lights, darks, flats, flat darks using the same reference frame as used for the L-Extreme data - Save as L-Pro.tif

- Stack these two stacks

 

Wouldn't this accomplish the goal of getting more detailed emission data, capture the reflection data, and add color to the stars?

 

Thanks,

 

Mark

I get better results by merging the two stacks together in post processing versus stacking them together. I've tried that in the past but all it did was average the colors so I lost some parts of each by averaging all the pixels across the image. When I have only a portion of the image I want to bring out I generally bring in each stack as a layer and then blend the sections I want. 

 

Give it a shot though. You may have better luck than I have.

[poolemarkw]

Thanks DirtyRod, I really appreciate your help.

 

Mark

[Drothgeb]

I just did my first image like this using Siril and Photoshop. It was three images, regular RGB, DualBand, and short RGB exposure for stars. Each image was stacked and minimally stretched in Siril. Then I used Siril to register and align the 3 images. Once that was done, I moved them to Photoshop. Base layer was from the OSC, Ha and Olll was added as a luminosity layer, then a separate layer of stars on top.

[poolemarkw]

Hi Drothgeb.   Was the OSC stack stripped of the original stars before bringing into Photoshop as the base layer?

 

Mark