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Chromatic Aberration Correction is now available in SharpCap 4.1

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#26 Borodog

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Posted 01 February 2024 - 09:19 AM

That is amazing. I am so happy to see you post those images, FSS. It looks like the extra glass is enough to keep the defocused blue under control enough that no extra filtering beyond the uv/ir cut is needed. That’s awesome. I hope that 140mm beast becomes an EAA workhorse for you.

 

Edit: Actually, looking closely, it looks like the part in bold is not actually quite the case. It looks like you still have some bloated halos on bright blue stars; they just aren't blue anymore. To get the full benefit, I would try adding a minus violet filter to the UV/IR cut. I think you will really like the results.


Edited by Borodog, 01 February 2024 - 01:40 PM.

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#27 roncarr880

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Posted 01 February 2024 - 07:32 PM

This is using the CA tool on an existing image.  The image is from a svbony 60mm F/4 guide scope, sv305c camera and #8 yellow filter.  I am not seeing a lot of CA with this equipment. but I have been compensating the lack of blue by using the Sharpcap image controls to boost the blue channel.  It is difficult to get a good color balance.  Anyway here is a picture with no adjustment and with DeepSky2 setting which I liked the best.  It just pops so much more than the slightly greenish original.

 

I am thinking with this new tool I can reset my color adjustment back to 128 for all channels.  Another thought is that I am surprised by the amount of blue one gets when the blue is not used at all.

 

gallery_481504_25210_25599.jpeg


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#28 Borodog

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Posted 01 February 2024 - 07:37 PM

Looks great, Ron!

 

It is good to see the pale yellow #8 working in action. I had only suspected it would perform well. I actually ordered and have one, but I have not had a chance to test it yet.


Edited by Borodog, 01 February 2024 - 07:40 PM.


#29 Far_Southern_Skies

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Posted 01 February 2024 - 10:02 PM

That is amazing. I am so happy to see you post those images, FSS. It looks like the extra glass is enough to keep the defocused blue under control enough that no extra filtering beyond the uv/ir cut is needed. That’s awesome. I hope that 140mm beast becomes an EAA workhorse for you.

 

Edit: Actually, looking closely, it looks like the part in bold is not actually quite the case. It looks like you still have some bloated halos on bright blue stars; they just aren't blue anymore. To get the full benefit, I would try adding a minus violet filter to the UV/IR cut. I think you will really like the results.

 

Yes, I had noticed the slight bloating. There is also a lack of colour in some stars where I would expect to see more. I am looking forward to experimenting live, to ensure accurate focus and have all the adjustment controls available.

 

As you say, I may have a killer EAA scope without the need for additional filters.

 

I have the Baader 495 Longpass and Semi APO filters from visual use and will experiment with these first. The minus violet could be a good option as it will block less of the useable light than these two.

 

I’ll keep you posted.


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#30 Borodog

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Posted 01 February 2024 - 10:19 PM

Not a fan of the so-called "semi-APO", which is pure marketing malarkey. It cuts out way too much well-focused light. But that 495 stacked with your uv/ir cut will work well I would wager.

 

By cutting out the defocused blue you will get better focus on the green and red as well.



#31 alphatripleplus

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Posted 03 February 2024 - 08:29 PM

I did some experimentation last night with an old f/2.8 135mm telephoto that has significant CA. I've been using it stopped down to f/4, and wanted to see how much improvement the synthetic blue tool makes in CA on a couple of targets. I used just a UV/IR block filter and Player One Neptune-C II camera.  I took identical 5 minute exposures  with: (i) regular blue channel, (ii) Deep Sky 1 synthetic blue channel, and (iii) Deep Sky 2 synthetic blue channel.

 

The first target was NGC2237, the Rosette Nebula, and the second was (more challenging), M45, the Pleiades.

 

 

Here are the comparisons for the Rosette Nebula:

 

NGC2237; (regular blue channel); 20 x 15 sec

 

 

NGC2237_UVIR_f4.0_RS_G300 2024-02-02T20_55_55_Stack_20frames_300s.jpg

 

 

Comment: Significant blue halos noticeable around brighter stars; click to zoom and the halos are easier to see,


Edited by alphatripleplus, 03 February 2024 - 08:57 PM.


#32 alphatripleplus

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Posted 03 February 2024 - 08:34 PM

NGC2237; (synthetic blue channel, Deep Sky 1);  20 x 15 sec

 

NGC2237_UVIR_f4.0_SyBDS1_RS_G300 2024-02-02T21_11_18_Stack_20frames_300s.jpg

 

Comment: Blue halos seem to be gone. Don't see noticeable halos in other colours.


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#33 alphatripleplus

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Posted 03 February 2024 - 08:37 PM

NGC2237; (synthetic blue channel, Deep Sky 2);  20 x 15 sec

 

 

NGC2237_UVIR_f4.0_SyBDS2_RS_G300 2024-02-02T21_03_13_Stack_20frames_300s.jpg

 

Comment: As with the first synthetic blue channel, the blue halos are gone. I also prefer the colour balance of the nebulosity with Deep Sky 2 vs 1, although I'm guessing that this could have been adjusted on the fly.


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#34 alphatripleplus

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Posted 03 February 2024 - 08:41 PM

Moving onto the Pleiades, which have a lot of bright blue stars:

 

M45; (regular blue channel); 20 x 15 sec

 

M45_UVIR_f4.0_RS_G300 2024-02-02T21_38_31_Stack_16frames_240s.jpg

 

Comment: Significant blue halos noticeable around most of the stars.



#35 alphatripleplus

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Posted 03 February 2024 - 08:46 PM

M45; (synthetic blue channel, Deep Sky 1);  20 x 15 sec

 

M45_UVIR_f4.0_SyBDS1_RS_G300 2024-02-02T21_25_08_Stack_16frames_240s.jpg

 

Comment: The blue halos are gone around all the stars. If you click to zoom, you'll notice that on the very brightest stars there is a weak colourless halo around them that seems to have replaced the strong blue halo in the original. However, the less bright stars seem to have both lost any blue halo they had, and have no new colourless halo. So this tool seems to be fairly effective even on a tough target like the Pleiades.


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#36 alphatripleplus

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Posted 03 February 2024 - 08:48 PM

M45; (synthetic blue channel, Deep Sky 2);  20 x 15 sec

 

M45_UVIR _f4.0_SyBDS2_RS_G300 2024-02-02T21_31_57_Stack_16frames_240s.jpg

 

Comment: Very similar result to first synthetic blue channel.


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#37 alphatripleplus

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Posted 03 February 2024 - 08:55 PM

Overall comment: On these two targets, I'm very happy with the results using Deep Sky1 and 2 synthetic blue channels. I'm impressed that using just a UV/IR filter and this tool can be so effective on CA with a fast telephoto lens. 

 

After looking at the captures, and zooming in, I could not find any noticeable increase in the noisiness of the background when utilizing the synthetic blue channels versus captures with the regular blue channel.

 

I don't do very much EAA in colour, but I'll definitely use this tool on achromats and  camera lenses going forward. Very nice work from the OP and Robin.


Edited by alphatripleplus, 03 February 2024 - 08:56 PM.

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#38 Borodog

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Posted 03 February 2024 - 09:57 PM

Overall comment: On these two targets, I'm very happy with the results using Deep Sky1 and 2 synthetic blue channels. I'm impressed that using just a UV/IR filter and this tool can be so effective on CA with a fast telephoto lens. 

 

After looking at the captures, and zooming in, I could not find any noticeable increase in the noisiness of the background when utilizing the synthetic blue channels versus captures with the regular blue channel.

 

I don't do very much EAA in colour, but I'll definitely use this tool on achromats and  camera lenses going forward. Very nice work from the OP and Robin.

Fantastic. I have to say I am impressed that no additional filtration is needed beyond the UV/IR cut. But I do want to warn people that I suspect this may be dependent on the scope, and maybe the target. For example, I have not seen any examples of planetary images posted in my MMPI thread on the synthetic blue channel method captured through achromats without additional filtration where the color balance was not utterly destroyed by color bleed of defocused blue light into the red channel in particular, and this method could not save those images in post. Although it occurs to me as I right this that, if they captured with no filter at all, not even a uv/ir cut, it could have mainly been IR that destroyed the red channel, not blue. 


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#39 artik

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Posted 04 February 2024 - 01:16 AM

Moving onto the Pleiades, which have a lot of bright blue stars:

 

M45; (regular blue channel); 20 x 15 sec

 

attachicon.gif M45_UVIR_f4.0_RS_G300 2024-02-02T21_38_31_Stack_16frames_240s.jpg

 

Comment: Significant blue halos noticeable around most of the stars.

Which scope is it?



#40 alphatripleplus

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Posted 04 February 2024 - 08:38 AM

Which scope is it?

In my introductory post of the series (post #31), I said:

 

" I did some experimentation last night with an old f/2.8 135mm telephoto that has significant CA. I've been using it stopped down to f/4, and wanted to see how much improvement the synthetic blue tool makes...."


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#41 Borodog

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Posted 04 February 2024 - 01:22 PM

After looking at the captures, and zooming in, I could not find any noticeable increase in the noisiness of the background when utilizing the synthetic blue channels versus captures with the regular blue channel.

 

What you will find is negligible change in the luminance, the color reproduction is very good, but the color noise becomes "two toned", as the noise in the blue channel is no longer independent of the green and the red, but a linear combination of the two. Personally I don't find this objectionable at all. It's an automatic "SCNR"-like process, i.e. "green noise removal" (which if you invert the image can be used as a magenta noise removal), because the method cannot approximate colors where G > R and G > B (i.e. greenish tints) or colors where G < R and G < B (i.e. magneta tints). 



#42 RMS82

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Posted 05 February 2024 - 04:33 PM

I tried this feature last night with my Optolong UV/IR filter which can give quite strong blue fringing on stars. Scope was Starwave Ascent 80ED F/5.6. Camera was a Player One Saturn-C (IMC 533).

 

The target was NGC 2516. 4 second exposures and 300 gain.

 

No CR reduction

 

NGC 2516 Stack 102frames 408s WithDisplayStretch
 
CA Reduction/Synthetic Blue=Deep Sky 1 (Blue=Green+Clip(Green-Red))
 
NGC 2516 Stack 101frames 404s WithDisplayStretch

 

Also tried Deep Sky 2 and found it quite similar to 1, but with a slight green tinge.

Edited by RMS82, 05 February 2024 - 04:34 PM.

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#43 Borodog

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Posted 05 February 2024 - 05:48 PM

Looks great. Personally, for pure stars without nebulosity I prefer the "solar system" method. It does quite well at reproducing the Planckian locus.


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#44 RMS82

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Posted 05 February 2024 - 07:38 PM

Looks great. Personally, for pure stars without nebulosity I prefer the "solar system" method. It does quite well at reproducing the Planckian locus.

Oh thanks, I didn't even think of trying the solar system one! Next time.


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#45 Borodog

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Posted 05 February 2024 - 08:38 PM

And when say “nebulosity” I mean specifically H alpha emission. Pretty much any broadband target including the Moon, planets, stars, galaxies, reflection nebula, you should be using the “solar system” method. I didn’t pick the names . :O)
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#46 roncarr880

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Posted 05 February 2024 - 10:19 PM

Flaming star nebula with method 2, B=G.  Borodog has me looking at color wheels but not understanding a whole lot.  But blue = green is cyan or darker versions of the same and Red is opposite on the wheel so how they mix is what I am not understanding.  Of interest in this image is the cyan colored hot pixels. 

 

My focus looks off or the 20mph wind was pushing things around, I think I cooked it a bit too much, 15 minutes and a lot of saturation.

svbony 60mm guide scope, #8 filter, sv305c camera.

 

gallery_481504_25210_131504.jpeg


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#47 Far_Southern_Skies

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Posted 06 February 2024 - 04:38 AM

Had my first chance last night to practice live, rather than simply trying examples through the test camera. Being able to fine tune adjustments makes a big difference to the outcome.

 

This is a follow up to the images in my early post - No.21, for the Carina Nebula. You can see the original blue bloated stars in all their messy glory.

 

Vixen NA140SS NEO ACHROMAT reduced to f3.9 with dedicated Vixen reducer. IR cut filter - no other filters. Deep Sky 1 CA Reduction.

 

NGC 3372,Eta Carina Nebula_2024-02-05_NA140SS at f3.9_SC_154X4.0s_616s_Gain300_Deep Sky 1 CA Reduction. Good seeing in Bortle 4 skies.

 

The stars are still missing some colour and there is a faint blue cast in the dark sky sections close to the red nebula - hard to see in the CN compression. Still, I am very happy with progress.

 

NGC 3372,Eta Carina Nebula_2024-02-05_NA140SS at f3.9_SC_154X4.0s_616s_Gain300_Deep Sky 1 CA Reduction.jpg


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#48 Far_Southern_Skies

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Posted 06 February 2024 - 04:46 AM

M46 and NGC 2438.

 

Another all star experiment using the new CA Reduction tool for my Vixen NA140SS at f3.9. IR cut filter only. Good seeing in Bortle 4 skies.

 

I am getting closer to finding the right SharpCap settings for good star shapes and colours. 

 

M46 (NGC 2437)_2024-02-05_NA140SS at f3.9_ASI585_SC_38X8.0s_304s_Gain300_Solar System CA reduction.

 

M46 (NGC 2437)_2024-02-05_NA140SS at f3.9_ASI585_SC_38X8.0s_304s_Gain300_Solar System CA reduction.jpg


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#49 Far_Southern_Skies

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Posted 06 February 2024 - 05:24 AM

Another follow up to the images in my early post - No.21, for Omega Centauri, globular cluster.

 

Vixen NA140SS NEO ACHROMAT reduced to f3.9 with dedicated Vixen reducer. IR cut filter - no other filters. Solar System CA Reduction.

 

NGC 5139,Omega Centauri_2024-02-05_NA140SS at f3.9_ASI585_SC_75X4.0s_300s_Gain300_Solar System CA reduction.

 

NGC 5139,Omega Centauri_2024-02-05_NA140SS at f3.9_ASI585_SC_75X4.0s_300s_Gain300_Solar System CA reduction.jpg


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#50 Borodog

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Posted 06 February 2024 - 07:35 AM

Those are gorgeous, FSS.

Getting brilliant star colors is a matter of other SharpCap settings; I promise you that the CA correction is capable of producing them. Check out Clouzot’s tutorial on good star colors in the other thread; it’s very good.
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