Imaging filter question

I just picked up a DSI pro II I and I have two questions. First, Is there anything special about the color filters used in imaging other then the uv block, and if not what filter numbers are used IE blue 80A. The other question is how and what are you using to keep the filter slide clean and safe when not in use.

Bob

Hi Bob,

I am no pro but here is my take on it.

Filters absorb light and allow a range of frequencies to pass to either your eye or a CCD. In your case its the latter and for most CCD imaging most people try to collect an equal amount of light across the visible spectrum to create an image close to what we think we would see. Actually we would never see these images but that is another story. These are called RGB images and use a combination of Red, Green, and Blue of equal (or close to) levels of transmission in their range to cover the visible spectrum; add a Luminance or clear to brighten the RGB image and it is an LRGB. Better filters are made with a balance between the three colors across the spectrum so the image is it's self balanced. Even better filters are made to compensate for deficiencies in certain CCDs or even focus the selected frequencies very close to the same distance creating an even more balanced image in color or focus or both.(there is a set for the DSI pro I believe). Most filters block UV and I am not 100% sure but I think the ultra violet frequencies may show up as a distortion in the lower frequencies on your CCD and UV may also have some unwanted reflective qualities due to it's high frequency. Some people (myself included) also use filters to collect light in ranges not visible to create an image or examine something our eyes may never perceive. (see image)

Your 80A is a common light blue filter used to raise color temperature from 3200°K to 4100°K which is another story and used in telescopes to make O2 more visible (I think its O2) by blocking or lowering the transmission of other colors. I don't think it would be a component of an RGB unless the other two filters have transmission levels close to the 80A and if so I don't think you will be needing a separate a Luminance image for that picture as those colors might be a little light.

Well there you go and remember I am no pro and my comments are just that, 'my comments and not fact'

The image is an 16 nm HA with the color added in Photo shop. like i said "no pro"

Enjoy

John 8)

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