Quote:
Originally Posted by nightstalker
I understand now that however well I can referance them the data I see regarding magnitude, and a lot of it is likely close , is still a little Arbitrary in regard to these historical catalouges ?
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There are several considerations with regards visual magnitudes.
For extended objects, the concept of magnitude itself can become a little
nebulous. For example, many extended objects such as some galaxies can
have what appear to be reasonably bright integrated magnitudes but their
overall surface brightness can be quite low.
Historically, many of the definitive observations of objects have been performed
by professional astronomers by way of various surveys. Many of these surveys
were conducted using glass emulsion plates and filters that had a different
frequency response compared to the human eye. As a result, many of the
visual magnitudes for objects are often synthesized estimates, using
inputs such as the magnitudes from the red and the blue plates combined with
corrections for the size of the object, the type of the object and so on. However,
wherever possible, a visual magnitude taken from direct visual observation is
used when available.
Quote:
(OPEN CLUSTER or BRIGHT NEBULA) with regard to ngc 2264 you have
nailed exactly what I did , in that ok your not showing up as a OC
so you must be a NEBULA , referance some more info still
get (no more objects )...haha.
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Just to clarify it, Argo Navis
will present you with NGC 2264 either if you
have searched for a NEBULA or an OPEN CLUSTER.
However, Argo Navis has the concept of a special magnitude selection called ANY.
Since NGC 2264 currently has not been assigned a magnitude, unless one uses
a MAG selection of ANY, then NGC 2264 will not appear in a tour.
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