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An 8" SCT only illuminates 38mm of field, so having an eyepiece with a 46mm field stop doesn't really make sense. There is a high likelihood you will see vignetting (light loss) at/near the edge of the field. If you stick with eyepieces closer to the widest field stop, like a 31 Nagler (42mm field stop) or even better a 35 Panoptic (38.7mm field stop), vignetting is less likely, and the higher powers will give a darker field of view and better contrast.
As for exit pupil, most people can tolerate up to 6mm of exit pupil, though it probably stops the scope down for most folks older than 50. My own pupils only open to 4.5mm at night, so, though I can use an eyepiece that produces a 6mm exit pupil, I know my eye is essentially stopping down the scope. The good news is that the light loss at such low power is usually not noticeable because I am not seeking the faintest objects at that low a magnification.
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