I Filter Effect

Usually we sellect RGB filters' range, 600-700、500-600、400-500 nm. These rages are based upon our human eyes' spectral response. CCDs' spectral range is wider than ours, so it will be different color if the filters' spectral ranges are different.
I know the red image role in color. Red image helps color image's colorfulness as the red rage is far from G and B. I sellected I filter instead of R filter and took M31.  

Left : RGB filters , Right : IGB filters

Filters and CCD spectral responses

The edge of M31 is enhaced in blue because this is due to the color distribution of M31. The red and yellow stars are concentrated in the center than blue relatively.
This I filter effect can apply to the Milky Way, Orion area, and so on. I will take those pictures, and look forward to seeing them.

Camera : Meade Pictor416XTE
Filters : IDAS UBVRI filter set
Optics : 180mm F3.5->3.75 Sigma APO
Mount : Takahashi EM-200
Guiding : without guide system, just star tracking mode

2000,11,3 original in Japanese
2000,12,8 translated in Enligsh