This area in Ophiuchus and Scorpius is a popular target for astro imagers and for obvious reasons. Whilst it is generally referred to as the RHO Ophiuchus Cloud Complex, the area overlaps from Ophiuchus into Scorpius and includes the Antares nebula as well as other deep sky objects in Scorpius. The colourful reflection nebulae make for a stunning and interesting field with the range of colours from blue to orange and red. Combined with this is are the deep brown colours exhibited by the dusty dark nebula that cross the field.

This image is a two panel mosaic captured with an ASI6200 full frame CMOS camera attached to a Canon EF200mm f2.8 prime lens. This combination is well suited for wide fields such as this one. It is, in fact, my first attempt at a mosaic with this set up and I'm pleased with the way that it has developed. It was also my first use of the Pixinsight Photometric mosaic tool which worked a treat and seamlessly combined the master panels very well.

The image is approximately 15 degrees across the diagonal and has been reduced in resolution by 50% for this posting. The full resolution JPEG comes in at 73Mb and the full resolution TIFF at a very generous 545Mb. One of the factors that must be contended with when using a full frame CMOS camera with small pixels is the large file size per capture, particularly when capturing un-binned data. Combine this with a mosaic capture and the numbers start to get quite big very quickly. One of the benefits of this configuration though is that the image scale of the full resolution image comes in at approximately 4" / px which is very good for such a wide field.

The area is comprised of multiple deep sky objects including emission, reflection and absorption nebula along with a number of well presented globular clusters. Included with this post is an annotated image produced in Pixinsight showing the different range of deep sky objects represented within the LBN, LDN, Sharpless, NGC and Messier Catalogue. (See image B). The star Antares is very prominent and accompanied by the globular cluster M4.

Interestingly, the only catalogued HII region in his field is Sharpless 2-9 surrounding the star Alniyat (20 Sco) and most widefield images of this area (including this one) are captured using LRGB filters only with no Ha data. Time and cloudy weather have prevented an attempt at Ha for this season which leaves a good target for next year when the object is back in view.