Tube diamiter?

[kc]

Is a 30mm diamiter better than a one inch diamiter?

[mackgee]

The way I understand it, the only thing you gain from the 30mm tubes is you have more windage and elevation adjustment than you get with the 1 inch scopes. Other than that you don't gain anything else.

Mac

[nratom]

Originally Posted by mackgee

The way I understand it, the only thing you gain from the 30mm tubes is you have more windage and elevation adjustment than you get with the 1 inch scopes. Other than that you don't gain anything else.

Mac

That's the way I also understand. Light gathering is not better with the same objective size.

[bruce_ventura]

To get 6X zoom range, I think you need to go to 30 mm.

[LouBoyd]

Originally Posted by bruce_ventura

To get 6X zoom range, I think you need to go to 30 mm.

That appears to be true, but I'd bet it's more driven by marketing than optical design necessity.

[bruce_ventura]

Read recently that the reason is mechanical. A 6X magnification range requires that lenses in the erector tube move further than for a 4X range. The power ring translates lenses via helical slots.

A single rotation of the power ring on a 1" tube cannot move lenses far enough for 6X. The helix angle in the translation mechanism would be too steep, requiring excessive torque. The same rotation of the power ring on a 30 mm tube can, however.

[Max Heat]

The terms 4X and 6X are not really proper, in this context. It would be more proper to state it in terms of power adjustability (zoom) RATIO, as in 4:1 or 6:1.