Thank you for all the replies. My main purpose in using this eyepiece is to achieve a wider field of view and more stars. I have other pieces for higher magnification. Hubble - the Explore Scientific is a Plossl? What would you suggest for a maximum field of view in an f/5 newtonian without breaking the bank?
The number of stars that you can see in a single field of view depends on the true field of view (TFOV) and on the magnitude of the faintest star that you can see. For any given aperture, the faintest star that you can see is a function of magnification, especially at wide exit pupils. Regardless of how wide your own pupils open, you will be able to see much fainter stars with a 6-mm exit pupil than with an 8-mm exit pupil, and much fainter still at a 4-mm exit pupil.
Achieving wide TFOV is always a compromise. In general, eyepieces with wider apparent fields of view (AFOV) allow you to achieve larger true fields of view without compromising (or with less compromise) in terms of magnification.
In other threads, Jon has suggested the GSO 30-mm SuperView as an inexpensive wide-field eyepiece that doesn't compromise too much in terms of image quality. Based purely on the specs, your 40-mm eyepiece ought to deliver a TFOV around 2.8 degrees wide at 18.75X, compared to 2.7 degrees at 25X for the GSO 30-mm SuperView. For me, the extra magnification would be well worth the slight loss in true field of view.
Be aware that the arithmetic for TFOV in wide-field eyepieces isn't entirely reliable even if the stated AFOV and focal length are precisely correct -- which they often aren't, especially apparent field of view. That's because all eyepiece necessarily distort the image somewhat. To put that in a different way, the focal length at the edge of the field of view is never exactly the same as in the center of the field of view.
Another factor for me is that I get diminishing returns from larger apparent fields of view. I can take in almost the full field of view of a Plossl entirely, at a glance. With a 68-degree eyepiece I need to look around a bit, and the edge of the field is often a little hard to see (depending on the design and the focal length). With a 82-degree AFOV or wider, I find the edge of the field really difficult to see, even if I try hard. So for me, although an 82-degree eyepiece does indeed have a wider effective field of view than a 68-degree eyepiece, it's not as wide as the numbers suggest.
Despite the benefits of a wide apparent field of view, I still find something very solid and comforting about eyepieces with AFOV of 50 degrees or less, where what you see is really what you get. Most people feel just the opposite. Just saying ...