Newbie Question (sorry) 
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 Newbie Question (sorry)
I know this is a newbie question but... How do I find out the field of view
of my telescope?

Bryant Allen
Lat:  36.310357  36:18:37.285N
Lon:  -085.634043  85:38:2.555W

Wed, 20 Mar 2002 03:00:00 GMT
 Newbie Question (sorry)
Hi there.  You asked:

> I know this is a newbie question but... How do I find out the field of
> view of my telescope?

You can use a variety of methods.  The first is to compare the field you
see with the size of the moon.  The moon is about 1/2 degree across, so
if you can fit all of it in your eyepiece, your field is over half a
degree.  If the moon just fills half of your field of view, your field
of view is about a full degree.  You can also use the Pleiades star
cluster to judge field size, since a one degree field is about the
distance from Atlas to Electra.  A more rigorous method is to time how
long it takes a star to drift all the way throught the field of view of
your scope (ie: edge to center to edge).  The diameter of the field is
then given by the equation: d = 15*T*cos(delta), where T is the time,
delta is the declination of the star you are watching, and d is the
field diameter.  For example, if you have a star with a declination of
30 degrees and it takes 4.0 minutes for the star to drift through your
field of view, the field of view is 51.96 arc minutes across (about
0.866 degrees).  If you time is in minutes, the diameter of the field
will be in minutes of arc, and if your time is in seconds, the field
units will be seconds of arc.  You can also use a star on the celestial
equator and then forget about the cosine function, since cos(0) = 1.  I
hope this helps you.  Clear skies to you.


Prairie Astronomy Club, Inc.
Hyde Memorial Observatory,
*   Attend the 7th Annual NEBRASKA STAR PARTY   *
* July 29-Aug. 5th, 2000 *

Thu, 21 Mar 2002 03:00:00 GMT
 Newbie Question (sorry)
Good question, and IMO, no reason to be sorry...
     A good book I got is "The Backyard Astronomers Guide" by{*filter*}enson & Dyer.
It covers this question really well and tells you how to calculate things like
this very easily. Well worth it (IMO).

Happy gazing...

Thu, 21 Mar 2002 03:00:00 GMT
 [ 3 post ] 

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