Hi there. You asked:

Quote:

> 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. http://www.4w.com/pac

Hyde Memorial Observatory, http://www.blackstarpress.com/arin/hyde

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