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Old 20-04-2020, 11:03 AM
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NorthernLight (Max)
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Blending different camera exposures

Hi guys,

I couldn’t really find a useful workflow description to blend images by 2 different cameras with different values and image types in Photoshop or Startools (don’t want to get into Pixinsight yet).

Here is what I’m trying to achieve:

I’ve got a Baader modded Canon 450D and a Stock Canon RP. The 450 takes exposures through a Dual Narrowband on a 50mm f/1.8 while the RP is taking broad spectrum through a 70mm f/4.

How do I blend the final stacked images of both into a single image so that the narrow band data augments the broad spectrum in a meaningful way and I end up with a final image that combines the smoothness at high ISO of the RP with the colour and contrast gained from the narrowband shots of the 450?

Looking forward to any suggestions or ideas for further reading.

Cheers
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Old 20-04-2020, 11:53 AM
glend (Glen)
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From my perspective, this is about image scale. If you were using two 450Ds one modded and one not, and have taken shots through the same scope, then yes absolutely you could put them together. And in my experience, using Photoshop Layering this would be easy.
While it maybe possible to manipulate your final images to overlay, it's sort of like the old guy answering a question about directions to a location, saying " if I wanted to get to where you want to go, I would not start from here".
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Old 20-04-2020, 02:59 PM
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Not an ideal situation but trying to make do with what i got and nodding the RP is out of the question for the foreseeable future as it’s the offical family camera. I thought along the lines of up/down sampling the images and applying some layering techniques but other than trial and error I have no clue how to do this effectively in my limited time allotment for the hobby.

Hope some others can chime in too.
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Old 22-04-2020, 11:20 AM
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If it were me,


Make your RP data black and white and layer it in as a Luminance channel in Photoshop or GIMP.

To get them to try and line up, choose one image, and select it as a reference image in Deep Sky Stacker when you go to stack both sets of subs separately - hopefully DSS is able to align everything nicely for you..

cheers
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Old 22-04-2020, 01:42 PM
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Registar is the best program for aligning different image scale images.

I have used it several times that way. Data from different telescopes

Pixinsight probably would do it as well using Star Alignment.

You are not that far off as 80mm on full frame is equivalent to 50mm on APSc.
So you are a tad wide on the full frame right?

Greg.
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Old 22-04-2020, 07:17 PM
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RobF (Rob)
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As Greg said, Pixinsight would make short work of the alignment issue.

Then you get into the main game of deciding whether to do Narrowband + broadband, what to use for Lum, what is quality, what is better thrown away.....
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Old 29-04-2020, 03:12 PM
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NorthernLight (Max)
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Quote:
Originally Posted by rustigsmed View Post
If it were me,


Make your RP data black and white and layer it in as a Luminance channel in Photoshop or GIMP.

To get them to try and line up, choose one image, and select it as a reference image in Deep Sky Stacker when you go to stack both sets of subs separately - hopefully DSS is able to align everything nicely for you..

cheers
I thought along those lines but wouldn’t it be more useful to use the NB frames from the 450 as a luminance layer? Just how to overcome the pixel pitch and more than half the resolution is what I ponder 🤔
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Old 29-04-2020, 03:16 PM
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NorthernLight (Max)
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Quote:
Originally Posted by gregbradley View Post
Registar is the best program for aligning different image scale images.

I have used it several times that way. Data from different telescopes

Pixinsight probably would do it as well using Star Alignment.

You are not that far off as 80mm on full frame is equivalent to 50mm on APSc.
So you are a tad wide on the full frame right?

Greg.
If Registar does the alignment, does that mean it stacks them into a single output FITS or TIF for post production? And if so, what size/ resolution would one expect from these different cameras (12MP APS-C size or 26MP FF?
I’ll have to try Registar and see but wonder how it copes with those different colour infos and sensor outputs.
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Old 29-04-2020, 03:21 PM
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NorthernLight (Max)
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Quote:
Originally Posted by RobF View Post
As Greg said, Pixinsight would make short work of the alignment issue.

Then you get into the main game of deciding whether to do Narrowband + broadband, what to use for Lum, what is quality, what is better thrown away.....
The 450 has its shortcomings when it comes to noise. The RP is a total game changer in that respect. But I guess it cooks the RAWs very different having a DIGIC 8 vs DIGIC 4. I was hoping - naively - that I could get the best of both: a clean black sky with nice star colour and the Ha shining bright in good contrast.

PS: wish I could just buy an Ra but $5k for a SLR makes me wanna buy a ASI1600GT with filters 🤣 if only the piggy bank had so much fat
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