This is a "false-color" or "mapped color" image of the Pelican using narrowband filters to bring out structural detail, similar to the way Hubble Space Telescope images are often presented (e.g. Pillars of Creation). OIII, H-a and SII data were color mapped to blue, green and red, respectively. The golden brown color therefore denotes a strong mixture of H-a (G) and SII (R) at ionization fronts. RGB data were added for star color.
A picture of the imaging train on the FSQ-ED is shown below. This arrangement results in the focus tube extending only about 1/4". It includes:
Takahashi FSQ-ED with RoboFocus
Astrodon 92-98 mm adaptor for TAKometer
Astrodon TAKometer (cable not connected in this photo)
Astrodon CAA-APF (92mm – 2.7" female, 0.4" thick)
Astrodon Spacer27 0.15" long "washer" fitting over 2.7" threads
0.75" Astro-Physics 2.7" extension tube
Astrodon MonsterMOAG off-axis guider with Starlight Loadstar guide camera
Apogee AI-FW50-9R filter wheel with 9 50mm slots
Apogee U8300 with 3326x2504 5.4 mic pixels
The Takahashi FSQ-ED is an improvement over the original FSQ106N refractor, the latter of which had significant focus differences between red, green and blue.