luminance

[jonnyboy]

what exactly is luminance when using LRGB filter. any reply would be grateful.

cheers guys

[GordonCopestake]

Brightness?

[CELESCOPE]

Hi Luminance is unfiltered light . need a high signal to noise Ratio, rgb filters usually are binned 2x2 for sensitivity, i never use the lum filter mainly because of the LP where i live , so i use an Ha filter instead of the LUM , . this would be for capturing DSOs, for galaxies i would use the CLS filter for the lum part . hope that helps

Rog

[Astroman]

When using standard LRGB filters with a CCD camera, the image is actually taken in black and white through the filter. The colors are assigned by the software later. A "luminance" image is just the black and white image, or greyscale if you like. So brightness is fairly correct.

[MartinB]

The reason for adding a plain B+W layer to the image is to provide fine detail. The eye is much more sensitive to fine detail in B+W images than colour, so the fine detail of an LRGB is provided by the luminence layer. When combining layers it is quite common to blur the colour layers to reduce noise and sharpen the luminence. I tend to use a CLS filter but as Rog says you can also use Ha very effectively on emission nebulae. You don't actually need to filter the luminence layer at all.

[jonnyboy]

thank for your replies they makes more sense than the books i have they mainly just give you the time they have used for each filter.

cheers jon

[Astroman]

Well said, Martin.

[FLO]

... the fine detail of an LRGB is provided by the luminence layer.

Which is why it is better to apply sharpening to the luminance layer only...