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Janoskiss is right on the money.
The widest widefield available in a 1.25" format is the 24mm panoptic, which happens to have the same true field as a 32mm plossl.
A 40mm 1.25" plossl is a white elephant, in that you dont see any greater field than you do with a 32mm plossl, but suffer from a smaller AFOV and bigger exit pupil meaning the sky background is brighter.
The rule of thumb is if you want a greater true field than that provided by a 32mm plossl at 50 degrees afov, you need to go to 2 inch format.
For smaller fields, some people still buy in 2 inch format just for the convenience of having a collection with the same barrel sizes and not having to mess with swapping adapters in and out.
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