NGC 2251, NGC 2254, Basel 7 & Basel 8 -- Open Clusters in Monoceros
Four Unicorn Clusters in One Eyepiece View
Modern eyepieces with wide apparent Field-of-Views and fast refractors with short focal-lengths
are a welcome addition to amateur astronomy. For most of my life enjoying the stars, if you
wished for a wide field-of-view your only choice was binoculars. But then your magnification was
limited. Only in the past few decades have the glories of large complex, widely dispersed
clusters and nebula have become available to the visual amateur.
The star complexity around the Monoceros (Unicorn) Open Clusters, NGC 2251, NGC 2254,
Basel 7 and Basel 8, is a case in point. With an eyepiece that provides 100-degree apparent
field-of-view in my 155mm refractor (f7), I can get all four clusters within the same eyepiece view
using a magnification of 52x. I did explore and tease out details using higher magnifications, but
the overall view of the clusters in a wide two-degree field was far more esthetically pleasing to the
eye. The drawing circle is the view (although it really does not do it justice) through the wide field
eyepiece, but details (mainly details in Basel 7 and NGC 2254) using 137x was also incorporated
in the drawing.