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Old 23rd October 2014, 12:19 AM
holly holly is offline
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Default Thinking .

Thinking about the spotting scope and thinking of way's to fit one to a rifle ( nope ) it got me thinking about the side mounted rear lens . we have off set triggers , why not off set rear lens .the benifit being that the head would not be twisted around , no tension on the neck which you can get if in the aim for a while . you might be able to just twist the cheek piece around to the right , to bring your eye in lane with it . be good for spectacle wearers as well . looking through the middle of the glasses . ??? HOLLY
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Old 26th October 2014, 04:29 PM
cloverleaf cloverleaf is offline
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Personally I thought the link was an excellent read with generally well-thought-out testing procedures.. the tester evidently spent a hell of a lot of time conducting and writing the tests up so hats of to his commitment and to Steve for posting the link

Originally Posted by RobF View Post
Was considering they were testing a 42mm scope against a 56mm and saying the field of view was tight...
Rob, I think you'll find that objective diameter has no effect on a 'scopes FOV; being analagous to an aperture in a camera lens - i.e. FOV is constant but light transmission and depth of field change with varying aperture / objective lens diameter.

Looking at the FOV values for the 'scopes of same mag but varying objective diamter on the Hawke website supports this idea.

Originally Posted by RobF View Post
Dunno. Its interesting to see comparisons but I'm not wholly convinced when someone says the mag is the limiting factor and doesn't mention it's a made up number... it's like using the wheelbase of a car to select a test range.

There's a test for visual resolution and it doesn't involve using your eyes. You use kit because eyes aren't very good testers.

But the mechanical tests are interesting, and it's really interesting to see how almost as many shooters think things like rets and turrets are as important as optics. Which goes to show why we probably have the scopes we do out there and why we don't have the scopes we want or should need.

It probably shows why things like chairgun don't work as well... but it'd prefer to see how well a scope tracked not how well 20mils dialled exactly measured 20mils on paper. The March is punished for this, but if you read the breakdown it returns to zero as well as anything else, and suffers with the elevation adjustment range a bit and it's cant is as good as the top scope.

I'm not saying it's perfect, but marking it down so low because 1 click doesn't precisely match what it should be, yet it still actually tracks ok seems a bit harsh. All i want to know is that 55 yd's is dialled 4.0 each time. I don't care what 4.0 is compared to a measurement of 4.0 moa on a ruler. I just want it to go from 0 to 4 and back 1000's of times the same amount.

I guess it could be because a lot of shooters shoot by the numbers and ballistic programs unlike us which rely on shooting.
I think your last sentence pretty much hits the nail on the head. Ultimately, while these 'scopes are of specifications that largely suit the needs of air-rifle users, they're designed to be used by centrefire shooters who have requirements that differ somewhat from those wishing to use the glass on an airgun.

For example, the mag range might not be important to the FT or HFT shooter as the 'scope will most likely always be set to a single (possibly highest) mag setting. Conversely; someone shooting a .338 over ranges between 100 and 1000yds would probably very much appreciate a wider mag range from which to choose.

Similarly, as you say the correlation between stated and actual turrent adjustment increments may be of little relevance to us as we tend to arrive at hold over / hold under values empirically through testing. We can do this because pellets are cheap compared to centrefire rounds, while we choose to do this since, as you say, ballistics programs are limited for airguns and accurate ballistics information is much more freely available for firearms. Hence, it's a much more plausible and viable proposition for long-range centrefire shooters to use ballistics tables / software to ascertain correct POA at range.

I agree about repeatability though; a feature that's definitely important to everyone and an example of where the requirements of different users converge..
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Old 26th October 2014, 05:06 PM
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RobF RobF is offline
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Yes, sorry... FOV isn't to do with objective. You're correct. From the March's i've looked through they are tight because of their focal length, something that isn't published... but leads to better range finding... (in my opinion), because the longer focal length gives a shallower depth of field. But it also makes for a narrower field of view.

Talking to one company last year, they said their marketing dept had said their customers like the bright wide field of view so they could find targets easily. My comment was if their natural point of aim was half decent they'd be looking at it when they looked through the scope. They were a little taken aback to hear that some just got on with fixed 32-40-45x scopes...
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Old 4th November 2014, 08:21 PM
cloverleaf cloverleaf is offline
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Cheers Rob - tbh I'm still learning about optics as they're not my strong point

In my quest to better understand I've found a couple of interesting sites - there's this calculator which is useful for understanding about the relationship between the focal lengths of telescopes, their eyepieces and resultant FOV and magnification.

The wikipedia page on telescopic sights also gives a decent overview of the relationship between the optical parameters involved in a 'scope. It's interesting to note that eye relief is apparently dependent on focal length (which I didn't know before I read the page).

I think your point about high mag 'scopes raises two interesting points - a) again the different requirements of different user groups, and unfortunately b) that potentially marketing men are happy giving uninformed customers what they want rather than what everyone might actually need..

In other news I appreciate your Reznor / Cash reference
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