|
I think with solar viewing the exit pupil would not be terribly critical as the observing will be done during the day, in full Sun. Therefore the pupil will be virtually fully contracted anyway, so even an exit pupil of 4mm may be excessive. At night time however, it is dark and the pupils will be dilated considerably, making the exit pupil more important.
I have found that putting the Pentax XW-10 or 14 give a larger image, but because of the wider view (70 degrees) you can see the whole Sun (a Plossl is usually 55 degrees, I don't know what sort of view a Kellner gives). The larger eye lens also makes viewing much easier, the eye lens in the Kellner that comes with the scope is pretty small. All of the wider angle eyepieces I have seen have a much larger lens, so this may also help. Maybe you could try a wider angle eyepiece with a shorter focal length and see how you go. I think your thoughts of 9.5 to 12 is probably on the money!
BTW, the Sun is pretty boring at the moment, haven't looked at it for a couple of months now!
|