A Sagittarius Triplet
in Narrowband Mapped Colour
Click on the above thumbnails to view cropped regions of interest
This image of the Lagoon Nebula, Trifid Nebula and emission nebula NGC 6559 depict a chaotic and active Sagittarius starscape. These regions are actively undergoing star formation as large clouds of gas and dust coalesce under gravity to form newborn stars. Due to the brightness of these objects, particularly the Lagoon and Trifid, this region is a favourite amongst amateur astronomers.
In this image of the Lagoon and Trifid Nebulae, the object is represented in a different light as opposed its usual true colour depictions. Instead of the usual RGB method of obtaining true colours of deep sky objects, the image featured here is an emission-line filtered image which represents the nebula's chemical composition. In this case, the nebula is photographed using a modified version of what is known as the Hubble palette, in which three filters to isolate Sulfur, Hydrogen and Oxygen emissions are used. The data from these three filters are then mapped to Red, Green and Blue respectively to create a false colour composite as depicted above. Due to the overwhelming presence of hydrogen in the Universe, most of the objects photographed using this palette will therefore appear predominantly green, a contrast from the usual strongly red colours that ionized hydrogen emits when photographed in natural colour.
This object was photographed from a city centre with severe light pollution, although the use of narrowband filters helped to drastically the extent of its effects.
I have also shot this the Lagoon and Trifid in true colour with a narrower field of view, which you may view here.
Location: Toa Payoh, Singapore
Date(s): July & August 2017, September 2018
Telescope(s): Astro-Physics 130 GTX at f/4.5, Takahashi FSQ85ED at f/3.9
Camera(s): ATIK 16200, SBIG ST8300M
Mount: Losmandy G11/G2
Exposure: SII - 30min, HII - 4h, OIII - 30min
Image reduction, integration and processing with Pleiades Astrophoto PixInsight