1.25' or 2' ep's

[Jiggy 67]

I've just took possession of a new SW 200P DS, which is currently looking sexy as hell in my conservatory. I already have a collection of 1.25' ep's from my previous scope. My question is would I gain a huge advantage by investing in 2' ep's or should I just stick with my current ones??....what are the differences between the two sizes??

[Moonshane]

there's no real difference between the two but you can get a wider field in the 2" eyepieces so for 16mm+ they are useful. That said, a 32mm 1.25" eyepiece is also excellent. many people have only one 2" eyepiece (myself included despite having a total of 12 eyepieces) as a widest field/finder eyepiece. for this purpose, I would certainly recommend at least one.

assuming your scope is f6 then you'd be pretty much OK with an eyepiece up to maybe 32mm in a 2" as any more than this and you may find the sky washes out due to the large exit pupil. f6 is also not too harsh on eyepieces but you'd gain in buying a decent quality one.

[GazOC]

A 32mm Plossl will still give you the same view in 1.25" as in 2" but if you go to longer focal length eyepieces and/or eyepieces with a larger field of view then the 2" will show more.

As a rough rules of thumb if the focal length of the eyepiece multiplied by the apparent view of view of the eyepiece is greater than around 1650 then its too wide for a 1.25 fitting and a the 2" will show more.