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Field Of View Calculator

If you want to get a better idea of the field of view (FOV) of different eyepieces or CCD cameras when used on a particular optical system (scope), Jesús Rodríguez has created a small application called What U See.  He offers two versions on his Web site - the older Version 1 for Windows 3.X works better for a screen view than his newer version 2 for Win9X, because it includes a view of the Andromeda galaxy (M31) that helps you see what the eyepieces are showing.  But his version 2 prints better because that same galaxy interferes with the eyepiece circles in the printout.

Below is an image of What U See version 1. Note that the fields of view of the eyepieces listed, are displayed superimposed on the photo of the galaxy on the right. (The yellow square of the TC-237 camera’s field of view is also displayed but hard to see here - it is inside the red circle of the 8mm eyepiece.  This small field of view for affordable CCD cameras is why you need a focal reducer if you want to shoot deep-sky objects.)

There are two other sites that you may also find helpful for CCD cameras.  Ron Wodaski's Magic CCD Calculator page shows a CCD's field of view (for different scopes and CCD cameras) along with a number of deep-sky objects shown, so you can an idea of what to expect for various combinations of equipment. Similarly, the Astronomical Society of Southern New England has a free down-loadable software application that allows you to see the field covered by commercially available CCD cameras. (Wodalski’s is better but it isn’t a stand-alone application like the ASSNE one or Jesús Rodríguez’- you need to use his on the Web directly.)

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