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Old 10-12-2009, 08:33 AM
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tnott
Oblonnygox

tnott is offline
 
Join Date: Aug 2006
Location: Adelaide
Posts: 221
I have tried various televue eyepieces in an 18 inch F4.5 and found that the paracorr made a big difference to the sharpness at the edge of the field in all of them. Stars were much more pinpoint at the edge and more stars were visible due to their light not being spread out as much.

It won't help the astigmatism you get from cheaper wide fields not handling the wider cone of light in a faster scope much (ie seagulls), just coma (ie comets).

I obviously keep it in the focuser of my 22 inch 3.6 scope the whole time.

It also flattens the field, which is good for eyepieces with some field curvature like the 28mm UWAN.

I notice less difference in an F5 scope, but the new owner of the 16" F4.9 scope I built now uses one and likes it.

The 15% reduction of the true field seems trivial to me compared to the improvement of the view. It is fairly heavy though, so may require counterweight on a LB with its small diameter side bearings.
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