This post presents a narrowband version of the area surrounding the two very well known objects: Messier 16 (Eagle Nebula) and Messier 17 (Omega Nebula).  As part of the same data acquisition activity, broadband data were captured with the LRGB filters and combined with Ha  and is presented as a separate post here. The combination of the ASI6200 full frame CMOS camera and Canon EF200mm prime lens is ideal for these widefield vistas and with the addition of narrowband filters allows one to show off the emission line data present. Image calibration, integration and post processing were completed in Pixinsight and a modified SHO palette was used as the starting point for the narrowband master. The predominant signal was from Ha with strong OIII also present as well as a significant contribution from SII. The presence of OIII is apparent in the teal colour surrounding the wider field. For interest, Revision G has been added to this post which as a copy of the narrowband master produced using the Pixinsight Pixelmath process after a basic stretch and before any further processing steps were applied.

The processing methodology deployed in working with the narrowband master was to acknowledge the strong presence of Ha and that of OIII in the wider field whilst also supporting the significant contribution of SII. This was achieved with the use of curves to work with the respective emission line colours and the development of masks specific to the Ha and OIII emission bands. Of course, where we land with the colour palettes in these narrowband images is always going to be subjective and your author likes it so that is the main thing .

A mouse over image has been added using the Pixinsight render tool to show the main deep sky objects present in the field. This mouse over image is available as Revision F for those that want to peer closer at the identified objects. With an image scale of approximately 4" / Px, a reasonable amount of detail is available in the final image. Note that the image for this post has been reduced to 60% of the original resolution to assist with image display and download speed.

With the number of objects in this ten degree wide field, it can also serve to provide a hit list of targets for subsequent data captures with longer focal length rigs. For interest, some of the better known objects present in this image are listed here:

• Messier 16 (Eagle Nebula)
• Messier 17 (Omega/Swan Nebula)
• Messier 18 (Black Swan Cluster)
• Messier 24 (Small Sagittarius Star Cloud)
• Messier 25 open cluster

My thanks to @Niall MacNeill and @Peter Rejto for providing feedback on this image prior to publishing.

Clear skies,
Rodney