Many observers, however, are surprised by how difficult it is to see the Trifid through binoculars. Like M8, M20 is a combination of an open star cluster surrounded by faint tendrils of nebulosity. The open cluster portion of M20, cataloged separately as NGC 6514, is a tight collection of 70 stars spanning half a degree. It’s the collective glow of these stars that many misinterpret as the Trifid Nebula. In reality, they are really only seeing the Trifid Cluster. Again, from dark skies you’ll be able to see both.
I have never spotted the intertwining lanes of dark nebulosity that give rise to the “Trifid” nickname through my 10x50 binoculars. They are, however, fairly evident through my 16x70s. What is the smallest binocular that will show them? I would be interested in hearing your results.
Open cluster M21 is just half a degree northeast of M20. Its 70 stars are packed into an area spanning less than a quarter of a degree, so things are tight. Most shine below binocular threshold, although a few individual points of light shine through the soft glow formed from the rest.
I’d love to hear about your binocular conquests. Email me at
binophil@outlook.com.
The area around M8, M20, and M21 is lovely for just idly stargazing on a warm August night. I hope you’ll get out and enjoy all there is to see here the next opportunity you get. And as you do, remember that two eyes are better than one.