1.25'' VS 2'' and other newbie ponderings...j

[Sonicfishcake42]

Hi all, 

I was just wondering if you kind folk can help me understand the following things a little better, bare with me... i'm new to this and i'm sure plenty of silly questions are going to be involved! 

First of all, when I see the term 'field of view' does that mean (here comes the silly question) the amount of sky visible in the eyepiece? i've noticed with the cheap EPs that come with telescopes the higher power magnifications 6mm, 8mm, 10mm have progressively smaller circumference openings in the EPs... with some of the more expensive EPs their seems to be a much larger circumference 'view hole' (for lack of a better phrase). So for example it's like looking at the sky through a straw VS looking at the sky through a tube?

is this (or related to) field of view?

And with a more expensive EPs with lets say 8mm magnification do you see more of the sky at the same magnification than a cheaper budget version? Would this be due to cost and manufacturing of the glass

Secondly of course you can get 1.25 and 2'' Eps, does a 2'' EP directly affect how much of the sky is visible through the lens? Meaning do you see more through a 2'' than a 1.25''? if not what is the benefit/difference between using either size lens?

I've seen 1.25 to 2'' diagonals allowing you to use existing 1.25 scope barrel to attach 2'' eyepieces -OR- alternatively you can buy a 2'' visual back for the scope to take the existing 1.25 off and replace with a 2'' meaning any 2'' equipment can be used without the aforementioned adapter. My question is do these both form the exact same function and have absolutely no difference between one another? or is replacing the visual back better than buying an adapter?

So does a 2'' EP in a 2'' visual back perform exactly the same as in a 2'' diagonal converter?

Thanks in advance! 

James 

[-Aldebaran-]

The more expensive eyepieces you refer to probably have a higher Apparent Field Of View, which is usually measured in degrees° your 8mm eyepiece with a higher field of view, say a 68° will show more area of sky than an 8mm with 50°

2" eyepieces generally have longer focal lengths / lower magnification, and require this larger size to get the full view in the eyepiece.

[Gino Arcari]

Hi James, i put up a topic not too long ago similar to what you're asking, perhaps having a read through will help you understand a bit more about 1.25" and 2":

http://stargazerslounge.com/topic/242213-choosing-a-new-eyepiece/#entry2629143

[Sonicfishcake42]

Perfect, thanks for the link Gino!

So I'm clear the 2'' lower power EPs use the 2'' for higher field of view where as higher power EPs are usually always standard 1.25'' however with the multi 1.25/2'' hybrid higher power EPs only have the 2'' option for extra security/stability? With essentially little or no impact on how much you can see?

(just want to make sure I'm clear) 

Thanks for the help! 

[Gino Arcari]

Yes thats correct I can also imagine them making the hybrid eyepieces to make it easier to use with different telescopes whether its a 1.25" telescope fit or a 2" fit,  and no problem James, I'm happy to help, 

[triton1]

Yes my higher power eps are hybrids wheras my two lower ones are 2inch only.This helps so I don,t have to faff around with an adapters.Also a lot easier to hold when wearing gloves,you can,t poke your eye out(like I did once with a volcano top,noob mistake)and the screw up eye cups are very comfortable