The benefit of RGB imaging

[mswhin63]

Hi All,

Thought I would show by pix some of the issues experienced by myself and most probably many other.

Most beginners use straight colour cameras and this is a really good start, I have now realised the benefit of RGB, although I don't have a mono camera yet i expect that I will evenutally.

I no longer have time for imaging for a while now so for tonight thought I would see what I could do reprocessing some of the close up moon images.

All my images of the moon using a barlow never felt right, slightly blurred so I split the images into their components RGB and saw my Red was the only colour in focus. This issue is more to do with my Barlow lense than anything else as without the barlow these images are great with no colour issues at all - http://www.waelect.com.au/mswhin63/Malcolm%20Whinfield%20Astro%20Photo graphy/Moon%20-%20Wide%20View/index.html#8

Attached is some images:


RGB Original
Red only
Green only
Blue only
Red re-processed to final image.


Hope someone will get some benefit from this. I know i have especially with some of my deepsky stuff.

[mswhin63]

Forgot to mention the cause of the is Chromatic aberration from the Barlow (thank-you Rally for reminding me :thumbsup: ). If you cant afford a Power mate like me at the moment to get the best image would be to place filters in front to separate RGB and focus on each colour.

Another way mention by Bojan in another Deepsky image post is to off adjust the the focus in one direction to find the sweet spot for each colour. I have tried this on my 450D with 75-300mm lens and works but is better with filters.

[multiweb]

There is a 'all in one' barlow system from Baader called a FFC. It is a small fluorite quadruplet that will give you anything between x3 to x8. I have been looking a long time at powermates and the like. Problem was the price for me so I bit the bullet and paid a bit more for this knowing it would give me more flexibility in choosing magnification, works with various scopes and has flawless colour correction if you use an OSC. Of course if you put it on a refactor it'd better be an APO. Still cheaper than buying an assortment of various powermates.

[irwjager]

If you have troubles like these because of CA, then make sure it's the green channel that is in perfect focus, rather than the red or blue.

The reason for this is that a single pixel on your typical OSC or DSLR is recorded by two green sub-pixels and only one blue and one red sub-pixel.

Debayering and using only the red channel is throwing away 75% of your data, whereas debayering and using only the green channel is only throwing away 50% of your data.

Additionally, you could decide to use your green channel as a luminance channel and recomposite your image. This way your image is sharp and it's still in color (though brightness in some areas may be slightly off due to the missing brightness contribution of the red and blue channels).

[mswhin63]

Many thanks :thumbsup: This is really great to know, had a quick look at the product, wow quite impressive. I know I use a DOB but to have such a variable magnitude is awesome in it own right. It will take some time to get the mullah together but it does seem to be the answer.
My optics are good (not perfect), but for CA as seen from the link to the moon done without a barlow the only color issue with that is a distorted CCD from excessive stress.



That is also good advise, unconditionally a lot of my Deepsky is done show green in focus, plus this was also imaged before I purchased the remote focuser so the focus is rough. I am going to go through a lot of my images one at a time and replace them where necessary although Jupiter images are not going to be easy to deal with.
The post was really to help with some aspect of imaging and already the additions will be of great benefit.

I think if I am going to do detail imagery I would still go for mono CCD camera and LRGB filtering so that all the pixel are covered by all colours.