What would a 2" diagnoal give me on my CPC?

[evilgeenius]

Hi

I have a CPC 925 with some 1.25" eyepieces and all is good.

I'm wondering what using 2" eyepieces would give me that 1.25" can't?? Is it simply wider field of view?

It seems as though the standard is 1.25" and no-one seems to mention 2" eyepieces. Isn't it a waste though?.. missing all that light round the edges?

Also, how does using 2" eyepieces affect imaging?

Cheers

Chris

[John]

I'm not an imager so I can't comment on that but visually 2" eyepieces give you a wider field of view than 1.25" ones. As an example, in the 1.25" size a 40mm focal length eyepiece can deliver a maximum effective field of view of 44 degrees wheras, in the 2" fitting, 70 degrees is possible which shows a lot more sky in the scope.

[Mr Spock]

With the C9.25 you can manage a real field of around 1.3°. This is down to the size of the baffle tube. I can get this with my 42mm LVW, a 2" eyepiece. However, it costs a whopping £300 and you need to add on a 2" diagonal.

For 1.25" the maximum would be a 68° 24mm Hyperion at x98 and 0.7°. You can add a focal reducer, giving 1.1° with the Hyperion.

You can't get wider with the focal reducer and the 2" eyepiece mentioned above. The size of the baffle tube is the limiting factor with any SCT, so the focal reducer does nothing for you; it does reduce aberrations, but it also increase the amount of glass in the light path. The size of the focal reducer aperture can also reduce the field size.

[faulksy]

With the C9.25 you can manage a real field of around 1.3°. This is down to the size of the baffle tube. I can get this with my 42mm LVW, a 2" eyepiece. However, it costs a whopping £300 and you need to add on a 2" diagonal.

For 1.25" the maximum would be a 68° 24mm Hyperion at x98 and 0.7°. You can add a focal reducer, giving 1.1° with the Hyperion.

You can't get wider with the focal reducer and the 2" eyepiece mentioned above. The size of the baffle tube is the limiting factor with any SCT, so the focal reducer does nothing for you; it does reduce aberrations, but it also increase the amount of glass in the light path. The size of the focal reducer aperture can also reduce the field size.

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