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Low Light Scopes & Magnification Qs for the Gurus!

 
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  #1  
Old 09-20-2011, 03:33 PM
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Join Date: Oct 2010
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Low Light Scopes & Magnification Qs for the Gurus!

Currently have a 3-9x40 VX-II on a .30-06 that I use mainly for whitetails up to 400yds. Most of my good opportunities come at dawn/dusk, and my VX-II is just plain terrible for gathering light (for my eyes anyway). I wind up watching the game thru my good binos clear as day, but not enuff good light in my VX-II to take a responsible shot. So, w/ that as background, what good light gathering scope would you guys recommend in the under $800 range? So, again, good, bright light gathering is key for me.

My assumptions are that I probably need a 50mm objective lens, but can stick to a 1" tube and don't need the 30mm tube. I understand that I can drop down in the size of the objective lens, and get the same light gathering as a 50mm, but that probably puts me in the stratosphere of scope prices.

Also, do I need more than 14x magnification? I wanna leave room to extend my range well beyond 400yds with time (and don't want to buy a new scope to do so), but I'm not an Army sniper, so do I really need the 20X mag that everyone tries to sell me? Seems like that extra money on mag would be better spent on better glass.

Finally, what about reticles? I have the basic plex in my VX-II, but everyone is running to the fancy bullet drop compensation stuff, etc. Seems to me that only clouds up the view, and makes it seem darker.

Insights/suggestions would be very appreciated.
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  #2  
Old 09-20-2011, 04:14 PM
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Join Date: Mar 2003
Location: Southern Wisconsin
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Re: Low Light Scopes & Magnification Qs for the Gurus!

Well I'm far from a guru, but I'll offer my experience/opinion.

I have a Nikon Tactical, a Clearidge Ultra XP5, and 4 Zeiss Conquests. All of them are more than adequate for shooting during legal hunting hours even on the grayest most overcast days. All of those scopes were less than $800. Some were used or from Ebay and some were brand spanking new, but they all perform flawlessly.

Objective size is your choice, a 50 mm with 90% light transmission is not neccessarily clearer than a 40 mm with a higher % of light transmission. So shop wisely.

Magnification.....Man here's a tough one. I have 2.5x10 (smallest I own) and have on occasion wished for more power while looking at game. Shooting targets it definately leaves me wanting more. In the middle is a 4.5x14. I can't ever remember wanting more power in the field, but I have on the target range. On the top end I have 4.5x22.5 and 6.5x20 to me this seems perfect. Now some will say 6.5 on the low end is to big for finding things in the thick woods or finding running game and I would agree with this If you don't practice with it. It does take a little getting used to, but after a bit you don't even notice. I can turn the 6.5x20 down when needed or set it at 20 when I feel I need more magnification. Never been able to turn the 2.5x10 or 4.5x14 up to 20 when needed

Hope all this rambling helps a bit.

Chris
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  #3  
Old 09-22-2011, 12:58 AM
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Join Date: Oct 2007
Location: Patagonia Mountains, Arizona
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Re: Low Light Scopes & Magnification Qs for the Gurus!

here are some optical basics to think about.

The exit pupil of a rifle scope (any optical telescope) is the diameter of the light bundle where it enters your eye assuming your eye is at the optimum separation from the eyepiece. It is not a place where an image is formed. Images in a rifle scope exist only at the target, the first focal plane, the second focal plane, and on the retina of your eye.

If the diameter of the scopes exit pupil is larger than the iris of your eye the light which does not go through your iris ls lost and does not add to image brightness.

The diameter of a scope's exit pupil cannot be larger than the objective diameter divided by the magnification If the scopes exit pupil is smaller than the eye's iris the brightness of the image will be the area of you're eye's pupil divided by the area of the scopes exit pupil. That number is purely from the spreading of the light. It does not include any reflection or absorption losses in the optical components.

So the optimum magnification for a given objective size for the brightest image is to have the objective size divided by the magnification to be exactly the size of you're eye's fully open iris which is typically about 6mm for midlife humans. As humans get older the irises of their eyes get stiffer and don't open as large. For example, a 50 mm lens at 10x would fill a 5mm iris. That's why 3-9x50's have been popular for many years. A larger objective will not give a brighter image at that magnification. With any scope where the maximum magnification exit pupil just fills the iris the apparent image brightness will remain the same over it's range of magnification adjustment.

Image brightness isn't the only important factor to being able to see well in low light. When the human eye becomes dark adapted it loses color vision. That's because the eye has two separate kinds of sensor called rods and cones. Cones are color sensitive but they don't dark adapt. Rods have the ability to increase their sensitivity by about a factor of 1000 over the light level where the cones cease detection.
Rods and cones are not uniformly distributed over the retina In the fovea (the center of vision) there are lots of cones and only about 1% rods. Over the rest of the retina there is a higher density of rods than cones. The result is that the resolution of the dark adapted eye drops by about a factor of ten. Just above the limit of color detection you can resolve image with a 10 times better linear resolution than just below where color vision stops. So it takes a 10x scope just to restore the >resolution< of the unaided eye. No scope can make an image's surface brighter than it would appear with the naked eye. To do so would violate laws of physics. It really becomes impractical to put a scope with a large enough objective and enough magnification do much more than just restore your naked eye capability once light is dim enough for color vision to cease and the rods start to become dark adapted. To do that requires electronic devices like image intensifiers , integrating video cameras, or artificial lighting.

Today all but very junky scopes have decent coatings on all lens surfaces. Each air-glass surface without coatings will reflect about 4% of the light. Modern scopes can get the total loss down to below 10% light loss. When you look at the lens of a scope with illumination from behind your head the less reflection you see the better. Ideally you would see no reflection.
It's difficult to make coatings which stop reflections over all visible wavelengths. Dropping reflections from 10% total to 5% total is not nearly as important as dropping them from 20% to 10%. Don't expect any leaps in performance in optical scopes. The better brands are close to theoretical performance already.

The whole point is don't knock yourself out trying to find something which doesn't exist. If you need a scope which will allow good resolution beyond civil twilight (sun more than 6 degrees below the horizon) the practical choices are spotlights, IR illuminated image converters, image intensifiers, and perhaps thermal scopes. Any of those may be regulated by hunting laws, including hunting at all after sunset.

For more information on optical design and how it relates to the human eye I recommend this old (1962) military manual:
opti 502 syllabus
It's big but it's free to download. The manual is in .pdf format.

Last edited by LouBoyd; 09-22-2011 at 01:14 AM.
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  #4  
Old 09-22-2011, 10:33 AM
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Join Date: Jan 2011
Location: Northern Utah
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Re: Low Light Scopes & Magnification Qs for the Gurus!

I think if you looked through a Burris Signature select 4-16x44 you'd be blown away. They are amazingly bright and surprisingly sharp and cost around $500. It blew my brothers VX-3 out of the water as night time was approaching, I could shoot for 10 minutes longer than he could. That being said, his still made it past legal shooting hours and is ever so slightly sharper in bright daylight. I chose to go with the Burris because I liked the noticeably brighter image compared to the Leupold, and I saved myself a little money in the process.
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  #5  
Old 09-22-2011, 01:02 PM
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Location: Patagonia Mountains, Arizona
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Re: Low Light Scopes & Magnification Qs for the Gurus!

Quote:
Originally Posted by Browninglover1 View Post
I think if you looked through a Burris Signature select 4-16x44 you'd be blown away. They are amazingly bright and surprisingly sharp and cost around $500. It blew my brothers VX-3 out of the water as night time was approaching, I could shoot for 10 minutes longer than he could. That being said, his still made it past legal shooting hours and is ever so slightly sharper in bright daylight. I chose to go with the Burris because I liked the noticeably brighter image compared to the Leupold, and I saved myself a little money in the process.
I have one of the Burris "Signature Select" 4-16X44s. It's a good scope though I'm not "blown away" by it. Optically it does what it's supposed to do. Scope manufacturers treat their skilled optical engineers well, but they don't live forever and they can change companies. Not all scopes from a given company have equally good designs. Burris does have good optical engineers, though I'd question if their mechanical designers are also shooters. I own about an equal number of Burris and Leupold scopes. More of either of those brands than other brands combined. Personally in selecting a riflescope I'm much more concerned with aiming the rifle quickly and precisely than having picture window views. If I want to search the landscape I use binoculars which have a much greater field of view for the same magnification.

In comparing and terrestrial scopes there are many variables. One of the most important which few manufacturers even mention and none I know of actually specify is the loss of contrast (as opposed to brightness) caused by internal reflections within and between the various lenses. The amount of light lost is far less important than whether the lost light is absorbed or ends up spread over the image. It's difficult to specify or to make definitive tests but its most noticeable when looking at a relatively dark field like the side of a mountain not directly illuminated by the Sun while looking in the general direction of the Sun but with the Sun's image not visible in the field of view.

No commercially available rifle scopes can correct for atmospheric scintillation, absorption, or scattering which can vary a lot and change rapidly with time. Unless scopes are compared side by side in identical conditions visual impressions can be very misleading. Most scopes give their best visual resolution close to sunrise and sunset as long as there's enough light for your eyes to not be the limiting factor. Without direct solar illumination atmospheric scintillation drops dramatically.
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  #6  
Old 09-22-2011, 06:39 PM
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Location: Northern Utah
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Re: Low Light Scopes & Magnification Qs for the Gurus!

Quote:
Originally Posted by LouBoyd View Post
I have one of the Burris "Signature Select" 4-16X44s. It's a good scope though I'm not "blown away" by it.
I know that my buddies that shoot the VX-II's were pretty sad after they looked through my Burris because it honestly was a nicer brighter image. It's not going to blow anyone away if they've looked through really high end glass, but it doesn't take anyone long to see that the Signature Select is a nice scope.

To be honest I've never been really disappointed in any scope that I've looked through that costs more than $600 but I think they all have their pro's and con's. I guess that's kind of a lie, I wasn't overly impressed with the only Huskemaw scope that I've had the chance to shoot with, but that's only one scope and I only shot with it once so maybe my eyes were just tired that day.
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  #7  
Old 09-28-2011, 08:33 AM
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Join Date: Oct 2010
Posts: 5
Re: Low Light Scopes & Magnification Qs for the Gurus!

guys: thanks for all the advice; very informative.

What are everyone's thoughts on the Swarovski AV line? Think I tracked down a decent deal on a used 4-12X50mm w/ the BR reticle. Though I'm not all that crazy about the reticle (would probably prefer #4), how does this scope do in low light conditions compared to the Conquest and similarly priced scopes?

Also, has anyone had any experience with Swarovski honoring its warranty on a private sale (ie, purchase not from an authorized dealer). The research I've done seems to indicate that the actual terms of Swarovski's warranty does not allow for transferability if not purchased from an authorized seller/reseller, but Swarovski's CS will honor it - for now anyway.
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