The combination of Hα SII and OIII with RGB is more or less similar to the combination with Hα, OIII and RGB only. SII emission is very weak but strongly correlated with Hα emission.
Nearly 90 hours of exposure times were collected for this image.
Image orientation : North is on the right.
Date: Fourteen nights in August / September 2016.
Telescope: #1: Skywatcher Esprit Apo 80 / 400 with flattener. #2: TS Apo 60 / 260 (with reducer). Both telescopes were mounted parallel on Mesu 200 mount.
Camera: #1: Nikon D5100a. #2: MI G2-8300FW @ -25°C.
Exposure: #1: 150x300s + 71x240s+ 103x180s @ ISO 200. Total exposure time 22h23m. #2: Hα (6nm): 1x1500s + 15x1200s; Hα (12nm): 46x900s (16h55m); SII (12nm): 68x900 (17h00m); OIII (12nm): 132x900s (33h00m).Overall exposure time: 89h18m.
Location: Rhein-Main area, Germany.
Processing: MaximDL, Pixinsight.