Scopes 101 help

[WokMaster1]

Hi guys,

Total noob here when optics are concerned. I have been searching for a scope for my AR. Purpose is just fun target shooting 75-200 yards. I have been looking at Nikon Monarchs, ProStaff, Leupolds, IORs & the usual suspects. And the more I looked, the more overwhelmed i get with all the numbers.

1. what do all these numbers mean?
2. 33mm vs 1 inch tube? difference?
3. 3-9 X 40mm vs 3 X 9 X 33- flew right over my head.
4. what's the difference between a 50mm vs 20mm?

Is there a place to do some reading to understand what all these terminology, etc. A "Scopes for Dummies" book, website.

Please help! Thanks.

[New Shooter II]

Sorry, I can not help you. I am in the same boat.

I will be observing along with you.

[FatKatMatt]

Hi guys,

Total noob here when optics are concerned. I have been searching for a scope for my AR. Purpose is just fun target shooting 75-200 yards. I have been looking at Nikon Monarchs, ProStaff, Leupolds, IORs & the usual suspects. And the more I looked, the more overwhelmed i get with all the numbers.

1. what do all these numbers mean?
2. 33mm vs 1 inch tube? difference?
3. 3-9 X 40mm vs 3 X 9 X 33- flew right over my head.
4. what's the difference between a 50mm vs 20mm?

Is there a place to do some reading to understand what all these terminology, etc. A "Scopes for Dummies" book, website.

Please help! Thanks.

1. Which numbers?
2. If a tube is 30mm or 1 inch just means that the tube is 33mm or 1 inch thick. I do not know the individual merits of each, but there are more rings made for the 1" tube than the 30mm
3. If a tube is 3-9x40 it means that the magnification range is 3x to 9x, and the objective size has a diameter of 40mm. The objective is the largest part of the scope at the end. The smaller the objective, the less FOV (field of view) you have. However, the bigger you go with the same quality glass the less quality you will have
4. I assume you're referring to objective size; a 50mm is much larger than a 20mm. The smaller the objective, the smaller the scope, and the lower you can mount it in relation to the barrel.

[Mute]

Here's a basic breakdown using the following example:

3-9x40mm

In this example, the 3-9 is the magnification on a variable scope (3x through 9x). If you only see one number here (e.g. 10x40) it's a fixed magnification scope. The second number (40mm) is the diameter of the objective. That will be front-most end of the scope (towards muzzle).

The tube (1" vs. 30mm) is the main body of the scope. 1" and 30mm are the two most common, though there are other sizes. The larger this number is, the more adjustments you have available in the scope because the size of the body determines how much room the elements inside the scope have for movement.

That's the basics regarding the nomenclature on scopes. For additional detailed information regarding scope technology take a look at the link below. Although it's deals mostly with long range, tactical style shooting, the information is still applicable.

Link - PRACTICAL LONG-RANGE RIFLE SHOOTING - PART II: OPTICS

[WokMaster1]

Matt & Mute, thanks for the clarification & link.

[Technical Ted]

30mm tubes allow more light to be gathered by the tube.

3-9X40mm: variable 3 to 9X magnification; 40mm objective (front bell) diameter (Also determines the height of the rings you'll use to maintain clearance above the rifle reciever).

[Pthfndr]

The smaller the objective, the less FOV (field of view) you have.

This part is incorrect. This is from Leupold's FAQ:

Objective Lens vs. Field of View
Does a larger objective lens give a wider field of view? No. The larger objective lens will increase the diameter of the exit pupil, but will not change the field of view. The magnification level of the scope and its optical design actually determine the field of view.

[PistolPete75]

if your going 200 yards or less, i say get the Nikon Monarch 3-9x40mm . very clear glass, with a simple duplex or bdc. most important thing i think for this range is just really clear glass, and good eye relief. it also has 1/4 moa adjustments which is a plus for fine tuning, and i think it goes for $229 at midway. downside is that it does not have a mildot recticle, but you don't need it for 200yards or less anyways.

[aplinker]

if your going 200 yards or less, i say get the Nikon Monarch 3-9x40mm . very clear glass, with a simple duplex or bdc. most important thing i think for this range is just really clear glass, and good eye relief. it also has 1/4 moa adjustments which is a plus for fine tuning, and i think it goes for $229 at midway. downside is that it does not have a mildot recticle, but you don't need it for 200yards or less anyways.

For just a little more $ he can get the Buckmaster with the mildots. It's worth it, imho.

Also, the last number (in 3-9x40) tells you how much light collection there is. The difference between 40 and 50mm might seem small, but it's area that matters. That's 150% increase in light, which adds to perceived brightness. Size becomes more important as you increase magnification. I would say anything beyond 10X really needs a bigger than 40mm objective.

I'd heard people make mention of tube diameter making a difference in brightness, but from an optics standpoint it doesn't make sense. Anyone know why people say this?

[maxicon]

The tube diameter gives more adjustment range. A 30mm tube gives more MOA of horizontal and vertical adjustment than a 1" tube, especially when one is off center.

That is, when your horizontal adjustment needs to be off from center, that limits the amount of vertical adjustment, because the adjustments will run into the wall of the tube sooner as you get closer to the sides. The extra 0.2" diameter gives a bit more adjustment room.

There's a good overview of scope terms and technology here:

http://www.opticstalk.com/forum_posts.asp?TID=5027&PN=1

[chickenfried]

From what I've read 30mm vs 1" does not affect light gathering.

A few discussions on the subject

http://www.opticstalk.com/forum_posts.asp?TID=3828&PN=1

From the leupold website http://www2.leupold.com/resources/My...ndanswers.aspx

Advantages of a 30mm Maintube Does a 30mm maintube give you more light?

The principal advantages of the 30mm tube are added strength and increased adjustment range for windage and elevation. For example, the M8-12X (1" maintube) has a total elevation adjustment of 51 minutes. The Mark-4 M1-10X (30mm maintube) has 90 minutes. The percentage of light passing through a scope is a function of lens coating and optical design, and has nothing to do with tube diameter.

30mm tubes allow more light to be gathered by the tube.

[Mute]

This has seen alot of pass discussion. Most conclusions is that the increase in tube size has very little, if any effect on light transmission. Nothing like increasing the size of the objective.

[mike452]

The size of the objective determines light transmission and eye relief you get. The tube size can offer you more elevation adjustments.

[xenophobe]

30mm tubes allow more light to be gathered by the tube.

Actually, larger tubes make the unit more durable, and also allow for a greater range of windage and elevation with the reticle. A 30mm tube will not allow more light through than a 1" tube.

A larger objective will increase the exit pupil, transmitting more light.

[aplinker]

Actually, larger tubes make the unit more durable, and also allow for a greater range of windage and elevation with the reticle. A 30mm tube will not allow more light through than a 1" tube.

A larger objective will increase the exit pupil, transmitting more light.

Hmm.. How does the larger tube make it more durable? The adjustment part is obvious.

Light collection is increased by a larger objective, not transmission. Transmission increases have to come from improved clarity of the lenses and reduced reflection from surfaces (plain glass reflects ~4%). Just a terminology thing...