NGC 891 -- Spiral Galaxy in Andromeda
Ghostly Splinter of Light
NGC 891 is an edge-on spiral galaxy. Through large telescopes at dark sites or through the
eye of a camera this galaxy is divided length wise with a massive dark dust belt making it
one of the most impressive looking galaxies in the night sky.
At magnitude 9.9 one is led to believe that this would not be a super difficult target for smaller
telescopes under less than completely dark skies. Many 9th to 10th magnitude galaxies are
within easy reach under similar conditions. However, NGC 891 is not one of them. Its famous
dark dust belt saps the glow from this galaxy’s light reducing its surface brightness to 13.7
(magnitudes per square arcsecond). In the 155mm refractor from my suburban backyard this
galaxy is a real challenge, even on a good night. At low power it is at first invisible. With
some effort one can begin to tease out the slightly brighter core, but to see any glimpses of
the spiral arms requires more magnification and even more patience. In the drawing the
eyepiece star field was provided at 84x while the details in the galaxy was at 137x. The only
hint of the famous dark belt was when it was silhouetted against the bright core; I knew it
extended completely through the spiral arms, but outer sections of the dark belt were beyond
my ability to see.
eye of a camera this galaxy is divided length wise with a massive dark dust belt making it
one of the most impressive looking galaxies in the night sky.
At magnitude 9.9 one is led to believe that this would not be a super difficult target for smaller
telescopes under less than completely dark skies. Many 9th to 10th magnitude galaxies are
within easy reach under similar conditions. However, NGC 891 is not one of them. Its famous
dark dust belt saps the glow from this galaxy’s light reducing its surface brightness to 13.7
(magnitudes per square arcsecond). In the 155mm refractor from my suburban backyard this
galaxy is a real challenge, even on a good night. At low power it is at first invisible. With
some effort one can begin to tease out the slightly brighter core, but to see any glimpses of
the spiral arms requires more magnification and even more patience. In the drawing the
eyepiece star field was provided at 84x while the details in the galaxy was at 137x. The only
hint of the famous dark belt was when it was silhouetted against the bright core; I knew it
extended completely through the spiral arms, but outer sections of the dark belt were beyond
my ability to see.