Well I have been having fun with my PST for some weeks now, in spite of a dreary sun surface. But I am not getting the best out of it due to my lack of suitable EPs.
The 20mm Kellner EP that comes standard is pretty useless as the image, though sharp is very small. I do a lot better with my 15mm Plossl, but still not enough detail. I have been advised that some folk use around 10 - 12mm EPs successfully. So I tried the Kellner with a 2x Barlow. Now I am closer to 68 than 67
so things like eye relief and exit pupil are important to me as my pupils don't contract as much as those of a younger person.
I cannot get any joy out of the 20mm plus Barlow as the exit pupil seems to be very large. I have calculated that the exit pupil with the 20mm given the 40mm aperture of the PST is 2.00 and I can handle that. But I don't know how to calculate the exit pupil with the Barlow. I suppose its academic really as I just get to see a blob of orange/red instead of a decent image unless I pull my face away from the EP and look around the edges of it for just glimpses of a much larger limb. Any ideas on how to work out the exit pupil with a Barlow?
Cheers!
Bert