30 mm scope tube ?

[btmj]

What are the advantages to a scope with a 30 mm tube, compared to a 25 mm tube? Particularly in a low power application like a 1-4X scope?

Thanks !

Jim

 

[CTS]

The first thing that comes to my mind is better light gathering qualities. In other words better performance in low light.

 

[zoomie]

More internal adjustments. The objective lens size and lens quality are more important for light gathering than the tube diameter.

 

[CTS]

I was assuming the difference in tube diameter was with all else being the same. So are you saying a 3-9x40 in 1" tube would not gather less light than the same scope in 30mm?

 

[zoomie]

I'm saying "light transmission" is way down on the list of reasons to buy a 30mm scope. You buy a bigger objective lens if you want more light; you buy a bigger tube if you want more internal adjustments. Other benefits are gravy.

 

[CTS]

Thanks, that is good to know. Sorry for being ignorant here but, what do you mean by more internal adjustments?

 

[zoomie]

The crosshairs have more range of motion. For dialing elevation and windage, you move your point of aim X MOA or mils up/down/left/right. 30mm tubes allow you to dial more correction before reaching the scope's mechanical limit.

 

[CTS]

Thanks again. I did not know that.

 

[bamaranger]

+1

Zoomies got it.

All factors need to be equal though. Lens quality, coatings etc.


Also, a 30mm with its larger range of adjustment, will allow the sight plane to remain near the center of the lense, for best clarity.