Specifications

● Color CCD chips have one fixed set of filters without the possibility to

exchange them or to completely remove them. Monochrome chip is

capable to take images with narrow-band filters like Hα, OIII, etc.

● Color chips have less Quantum Efficiency (QE) then monochrome

ones. Limiting QE from around 80% to around 30% by color filters

only wastes light in number of applications.

● Interpolation of pixel luminance from surrounding pixels, necessarily

performed when processing images from color chips, introduces

significant error and prohibits precise measurement of position

(astrometry) and brightness (photometry).

● Color CCD chips do not allow reading of binned images.

● Color CCD chips do not allow so-called Time Delay Integration (or

Drift-Scan Integration).

Another huge advantage of monochrome chip is the possibility to combine

color images from three color images and one luminance image. Luminance

image is captured without filter, using maximum chip sensitivity. This

technique is often called LRGB imaging.

Inserting the color filter into the light path significantly reduces the amount of

light captured by the chip. On the other side the human eye is much less

sensitive to changes of color than to changes of brightness. This is why the

CCD chip can be binned when capturing color images to 2×2 or 3×3 to

significantly increase its sensitivity. Luminance image is taken without binning

so the image resolution is not degraded.

Let us note that imaging through separate color filters is close to impossible in

some cases. For instance taking images of some fast evolving scenes, like

planet occultation by Moon, imaging of fast moving comet etc. There is no time

to take separate exposures through filters, because the scene changes between

individual exposures. Then it is not possible to combine red, green and blue

images into one image. In such cases using a single-shot color camera is

necessary.

The color images can be combined in the (L)RGB Add Tool in SIMS. This

tool is thoroughly described in the SIMS User's Guide.