The third open cluster , Pismis 20 , contains 12 stars in a diameter of 4.5 arcseconds .
The third open cluster , Pismis 20 , exhibits a magnitude similar to NGC 5823 ( 7.8 ) .
The third open cluster , Pismis 20 , contains 12 stars in a diameter of 4.5 arcseconds but exhibits a magnitude similar to NGC 5823 ( 7.8 ) .