Home Forums Hunting & Shooting Hunting Optics Stoopid question: everything else being equal, does a 30mm scope tube gather ...

I have a double whammy. Cataracts beginning and am diabetic. So circulatory problems could begin. I try to have a Blood sugar reading around 89 to 90 first thing in the morning. My A1C 5.5 but hoping to be down to 5.4 next check. So hopefully the only serious concern will be the cataracts. Still would like to be told what principle of physics allows light to be gathered by glass. It can be transmitted through glass and manufacturers strive for the minimum loss, thus the coatings but a small amount of light is lost in impurities etc. Help me out. I can learn. RZ.

It's basically the same thing as setting out a couple of different size (diameter) buckets to catch the rain. At any given moment, the larger diameter bucket will catch / collect more rain drops than the smaller diameter bucket. The buckets themselves aren't doing anything to catch the rain; they're just passively sitting there.

The photons of light are passing through the objective lens. At any given moment, more photons will "hit" (pass through) a larger diameter lens as compared to a smaller one. In other words, the larger lens gathers (and starts to focus) more photons / light than the smaller one. It's all about the surface area of the objective lens.

Bob F.

Maybe "gather" is not the best way to describe what a scope does to light......to avoid upsetting some folks that like to play word games I use the word "enhance" {so the human eye can see it better}. That said, if you ever fried worms and bugs out on the sidewalk with a lens you might argue that if that isn't "gathering" light I don't know what is.
This is an extreme of looking thru a telescope. The glass takes light and "fixes" it so our eye can see it better. The problem comes in with the human eye itself. A telescope can only do so much and our eye can only process what it sees in that moment.
If you really want to see the results of "gathered" light you have to add something that will "absorb" and store available light. Something our eyes wont do. When you see photos from NASA, etc. that show a deep space nebula in full color that is not what you see looking thru even the best telescopes. It just looks black and white and the most magnificent and colorful nebula in the sky looks like a dull white fuzzball of light. That is because your eye can only process the image it sees now and it cannot store and stack light as it comes in.
Ad an astrophotography camera and a very long exposure and you see way more of the light that's out there your eye cannot see. You can call it what you want, or refuse to call it anything, but glass does change things as far as light in our eye is concerned.
Good optics are expensive and anything less is, well....less. I have owned/bought and used them all. Zeiss, Swarovski, Leica, Schmidt and Bender, Docter Optik, Kahles....the ones made in Germany will not let you down. That said, there are now some Asian scopes that are really not bad, but they just don't perform like European optics. Now, all that said, the best refracting astronomy telescopes are in fact Japanese. I believe if any of the German riflescope makers would manufacture an astro-scope it's very likely that it too would be the best. They have made a few in the past, but they are rare and expensive.
Bottom line, buy a Zeiss Diavari 2.5-10 and you would have to have a night vision scope to see better in low light!!!!!

Yes, and it has it's own aiming scope mounted on it too.

From first principles, the principle of least action is responsible.

Practically, the principle of refraction is what allows larger objective lenses to funnel more light onto the optical axis.

I think it's more so the size of the aperature - refraction is just bending of the light. Just remember that a reflector telescope doesn't transmit light through glass at the initial stage but relies on aperature diameter to collect the light.

Yes, yes...it's true. Also, many are unaware that leaving a variable magnification scope on the highest zoom setting will degrade and eventually burn out the optics.

let's get down to optical brass tacks: my eyes will be 74-years-old in a couple of weeks. they do not gather light like they used to do so. I want to see deer well enough to shoot at fewer than 400 yards 30 minutes after official sunset, and 30 minutes before legal sunrise, in Alabama. I don't like variables because I like to keep things as simple as possible. 6x fixed is preferred, and rare as frog's teeth - and even hen's teeth - nowadays. I've never spent more than $300 on a scope, but as this most likely will be my last rifle scope purchase, I am willing to go higher - maybe even much higher. I don't dial. I have zero interest in long-range target shooting. I have searched the Google world for simple, quality scopes, and am left frustrated. i'd prefer to buy new. I'd take a variable - but only if I have to do so. SWFA may - or may not - make another batch of 6x fixed. within 120 yards, my current scope - Sightron 1.75x5x 32 - barely gets me to the last of shooting light, on clear evenings ...

It's always amusing when people fully understand the question being asked but pretend they don't. How's the lawsuit going you lizard legged twat?

Then find yourself a used 6x Leupold, preferably the 42mm.

That meets the requirements you described.

Yes it’ll cost a bit more than $300. Although I think there was one on the Classifieds recently in that price range.

I agree that the aperture size does limit the solid angle over which light can be collected, but an aperture doesn’t collect light, it allows light to pass through. To a small degree for large apertures, diffraction causes divergence rather than convergence.

The specific question was around what causes glass lenses to gather light, and the principle that is responsible is refraction.

A fixed S&B would make him even happier, I’m sure.

It seems you need a scope with a high twilight factor.

Mr. Google tells us, "The twilight factor is a number used to estimate how well binoculars or spotting scopes perform in low-light conditions like twilight. It's calculated by taking the square root of the product of the objective lens diameter (in millimeters) and the magnification. A higher twilight factor generally indicates better visibility in low light."

This concept was brought home to me in South Africa when we tried to get a wildebeest at almost full dark. I was using a Leupold 3-9x40 scope set at 4x - twilight factor at that setting is 12.7. I couldn't make out squat, just the dark brush. My PH told me to crank the power to 9x, which would be a twilight factor of 19. Suddenly individual wildebeest shapes stood out against the dark brush background.

(Side note: Exit pupil gets a lot of press and it does factor into things, but note that the exit pupil at 4x was 10mm, the exit pupil at 9x was 4.4mm but I could see detail at 9x that I couldn't see at 4x. The area of light coming out of the ocular lens has some importance but don't let it override other factors, since a human eye - especially older eyes - can only handle about a 5mm pupil at most.)

Larger objective lens + higher magnification gives higher twilight factor. European hunters can shoot after dark (IIRC) and they really go for that - 8x56 scopes not being scarce.

A straight 6x42 isn't a bad choice but a 10x42 will really let you see things in low light. However, 10x might be a bit much depending on what other situations you'll be in. You said you don't like variables but depending on whatever other requirements you have, you might consider one.

3-9x50, 4-12x40 or 4-12x50 - those would all perform very well in low light.

All this is predicated on quality lenses and coatings but folks are making some very nice glass these days that don't break the bank.

what physics allow a larger diameter pipe to flow more water?

Does 30mm flows more light than 25.4mm (1") make sense now?

What is the pressure of the light flow?......

This is true up to the limits of the exit pupil (objective diameter divided by magnification) being maximized for your eye.

Just in case you’re serious, that’s not really how a scope works.

A photon’s momentum is Planck’s constant divided by the wavelength of the photon, p=h/lambda, and instantaneous force is equal to the change in momentum per unit time, F=h/(t*lambda), and pressure is the force of the number of photons, n, over the area of the glass, A, so (n*h)/(A*t*lambda).

Everybody likes a good clear scope. I don't know about all states, but in TX hunting/shooting is restricted to 30 min before sunrise & 30 min after sunset. Sunrise & sunset times are posted by the weather bureau. If your target is difficult to see it's probably too late to shoot & you should be heading for the truck already.

Generally, I try to leave before dark so I won’t be tempted to take a shot that might present me with a tracking job and dress/drag in the dark. Sometimes walking out quietly will give me a chance at something along the way. When I was young and desperate, I hunted dark to dark, but that never really helped me get more deer.

Conversely, going in at first light instead of before also has provided some chances, and some meat.