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I find that seven degrees of field is the "magic number" (that is, the optimal value) for a finder telescope (or an even wider field, if you can get one or make one). A seven degree field is twice the area of a 5 degree field, so this makes it much easier to find and recognize the star patterns.
I don't know why so many people put up with narrow field finders, or finders that do not show the field in its true orientation.
I recently obtained a really cheap 80mm F4 objective (320 mm focal length) of mediocre quality and put it in a tube, together with a 26 mm eyepiece of 65 degrees apparent field, which yields a magnification of 12.3x and a sky field of about 5.3 degrees.
This instrument is going to be mounted on the main telescope, and aside from being an effective but modest Rich Field Telescope, it will be useful in more precisely pointing the main telescope....yes, believe it or not, my telescope is going to have two finders, a 50mm and an 80mm !!
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