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4 Filters - R,G,B to make colour image with Mono - but whats IR Block used for?

Fordos Moon

By Fordos Moon
in Imaging - Discussion

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lensman57

lensman57

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Merrily imaging Jupiter tonight with RGB filters and Firecapture.

About to start processing, and wondering what the IR Block filter is used for when imaging?

Fordos Stupid Question no 23.

For planetary and normal DSO imaging you need to use the IR block as LUM filter. For full spectrum DSO imaging you use the clear filter as some people do DSOs with IR as part of the capture. Some galaxies for example emit quite a bit of IR radiation and if the capture is for research then you don't want to block these out and yes lack of IR will cause star bloat or those lovely magenta rings around the stars with less than well corrected ED scopes ( that is the case for most of us mortals ) in the blue region of the spectrum.

Regards,

A.G

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JamesF

JamesF

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If anyone can direct me to a guide for adding a luminance channel in Photoshop I would appreciate it!

Can't give you a URL, but from memory it goes something like:

Read your combined RGB image in as one image and the lum image in as another.  Cut/copy the lum image and paste it into the RGB image as a new layer.  Set the lum layer to be the luminance channel in the channels menu, twiddling the opacity to your preference and then flatten the image.

I think :)

James

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JamesF

JamesF

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Can't give you a URL, but from memory it goes something like:

Read your combined RGB image in as one image and the lum image in as another.  Cut/copy the lum image and paste it into the RGB image as a new layer.  Set the lum layer to be the luminance channel in the channels menu, twiddling the opacity to your preference and then flatten the image.

Does that give you enough to work with?  I'm no Photoshop geek, but if it helps I can note down what I do next time...

James

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Fordos Moon

Fordos Moon

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Does that give you enough to work with? I'm no Photoshop geek, but if it helps I can note down what I do next time...

James

Yep I reckon I can give that a go James with the blend option thank you as always I must owe you about ten pints!

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ollypenrice

ollypenrice

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I'm not a planetary imager but don't some of the experts use the red channel as luminance? Or is that only on the moon? The thinking is that the red suffers the least atmospheric molestation since it has the longest wavelength.

In Ps you can put a lum layer over an RGB layer and then, in the layers palette, open the Blende Mode drop down and select luminosity. Or you can convert the RGB to Lab colour mode, split the channels, then recombine them putting the luminance in as the L in the Lab drop down. The first method has the advantage of not requiring you to apply the L at 100% opacity.

Olly

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ollypenrice

ollypenrice

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Many thanks Olly. I will give that a go. For sure the red filter gave much better clarity than the green and blue, possibly even sharper than the IR filter.

Don't know why I put an 'e' on 'blend.' Old age. Worse to come!!

I think that you should always try things and see. I do lots of DS processing using experimental techniques and I find people don't seem to object until I confess to how I did it...

Olly

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Fordos Moon

Fordos Moon

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Don't know why I put an 'e' on 'blend.' Old age. Worse to come!!

I think that you should always try things and see. I do lots of DS processing using experimental techniques and I find people don't seem to object until I confess to how I did it...

Olly

The blend luminosity route seemed to work I just think I need to work on better captures. The 200P not the ideal planetary scope perhaps! Had a go at Mars last night, it was very wobbly out there but all in the name of progress!

post-26268-0-42897900-1397907834.jpg

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ollypenrice

ollypenrice

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The blend luminosity route seemed to work I just think I need to work on better captures. The 200P not the ideal planetary scope perhaps! Had a go at Mars last night, it was very wobbly out there but all in the name of progress!

attachicon.gif20140418-Mars.jpg

Well, you have real details showing there. Pretty exciting.

Olly

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Fordos Moon

Fordos Moon

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Well, you have real details showing there. Pretty exciting.

Olly

Thanks Olly. I am now back at work and looking at my images on a different screen - everything seems over saturated with colour! I think my laptop screen I work on at home must desaturate my images! Note to self - Be more subtle with wavelets and tone down the colour when working on laptop!

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JamesF

JamesF

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Thanks Olly. I am now back at work and looking at my images on a different screen - everything seems over saturated with colour! I think my laptop screen I work on at home must desaturate my images! Note to self - Be more subtle with wavelets and tone down the colour when working on laptop!

I have found it impossible to get a decent colour balance on my laptop display so far.  I find it much better on a proper monitor.

James

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