The Outer Limits

The constellation of Andromeda is of course host to the spectacular (and big and bright) M31, but my favorite galaxy in Andromeda is this one, NGC 891.  It is also fairly large at about 13 arc-minutes across (about a quarter of the diameter of the full moon) but is quite dim at magnitude 8.9 making it fairly challenging to see with the naked eye.  It is sometimes referred to as the “Outer Limits” galaxy since an image of it was used in the credits of an old TV show of the 1960’s by that name.

 I took two images of it using the observatory’s ASI533MC camera.  The image on the left is using a 127mm refractor with 40 stacked frames of about 21 seconds each for a total exposure of about 14 minutes.  The image on the left is using the Observatory’s 16” Cassegrain with 30 exposures of 10 seconds each for a total exposure of 5 minutes.  The longer exposure clearly provided more contrast and detail.  I would have taken a longer exposure with the big scope but it was being a bit wobbly on the equatorial axis that night and I couldn’t hold track very well.   

NGC 891 is believed by many to be a spiral galaxy seen nearly edge-on from our perspective.  The conventional red-shift theory puts it at a distance of about 27 million light years from Earth.