Before you can accurately test the centering accuracy of your LX200 you
must know the actual field of view (FOV) of your eyepieces. Calculating
the actual FOV based on the apparent field of view is a good
approximation, but for more precise results follow this method:

Point your scope at a star near the celestial equator (ie dec = 0 deg)
and near the meridian, turn off the telescope drive and time how long it
takes the star to cross the eyepiece's field of view with a stop watch.
The actual field of view in degrees is the time you measured in seconds
divided by 240 seconds. Just multiply by 60 to convert that number to
arc-minutes.

Here are my results on the following eyepiece on my 10-inch f10
(f.l.=2500mm)
12 mm Meade MA illuminated reticle - 10.5 arc-min
15 mm Televue Plossl - 15.25 arc-min
26 mm Meade Super Plossl - 27.25 arc-min
32 mm University Optics Konig - 30.75 arc-min
40 mm Meade Super Wide Angle - 55.5 arc-min (2-inch)

Now I can work the math backward and compare the *advertised* apparent
fields of view with the *real* apparent field of view:

12 mm Meade MA illuminated reticle: advertised 40 deg, real 36 deg.
15 mm Televue Plossl: advertised 50 deg, real 41 deg.
26 mm Meade Super Plossl: advertised 52 deg, real 43 deg.
32 mm University Optics Konig: advertised 50 deg, real 40 deg. (15 years
old eyepiece)
40 mm Meade Super Wide Angle: advertised 67 deg, real 58 deg.

This was quite a revelation for me! It looks like that generally
speaking the advertised apparent field of view is about 10 degrees more
than the real apparent field of view!! Let us know what your
experiences have been!

Regards,
Paul Markov
10-inch LX200 f10
http://home.ica.net/~pmarkov/astro.htm

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