Visit the SWFA.com site to check out our current specials. |
RifleScope School |
Post Reply | Page 12> |
Author | ||
Chris Farris
TEAM SWFA - Admin swfa.com Joined: October/01/2003 Location: Texas Status: Offline Points: 8024 |
Post Options
Thanks(0)
Posted: March/15/2004 at 18:17 |
|
Whether you are a novice or seasoned riflescope user, these definitions will assist in understanding the different components and considerations that go into the engineering of riflescopes.
Magnification The most basic characteristic of a given scope, magnification is simply a measure of how many times better you can see an object than with your naked eye. It's typically the first number you see in a scope's name. For example, the a 6x42 has a six-power magnification: Six times better than the naked eye. Variable power scopes allow a range of magnification for different hunting situations. In these scopes, the first two numbers, separated by a hyphen, indicate the range of magnification. For example, a 3-9x36 magnification can be adjusted as low as 3x, or as high as 9x.
Objective Lens Diameter
Ocular Lens
Field of View
Exit Pupil
Twilight Performance
Eye Relief
Parallax
Center Tube Diameter (1", 30mm, 26mm)
Stray Light
Lens Coatings |
||
Lewis
Optics GrassHopper Joined: April/02/2004 Location: United States Status: Offline Points: 1 |
Post Options
Thanks(0)
|
|
I would just like to thank you for the article it help me a lot. I been shooting for a while but did not know much about scopes. Thanks
|
||
md10/22
Optics GrassHopper Joined: January/31/2004 Location: United States Status: Offline Points: 11 |
Post Options
Thanks(0)
|
|
Great addition to the forum! I listed a link to this from RFC I hope it will draw some participation to this forum. I think this forum is a great supplement to the RFC forums!
|
||
dgolfers
Optics GrassHopper Joined: April/05/2004 Location: United States Status: Offline Points: 3 |
Post Options
Thanks(0)
|
|
ditto
|
||
jbyrd
Optics Apprentice Joined: April/09/2004 Location: United States Status: Offline Points: 21 |
Post Options
Thanks(0)
|
|
Thanks
|
||
Afrikaander
Optics GrassHopper Joined: April/21/2004 Location: Argentina Status: Offline Points: 7 |
Post Options
Thanks(0)
|
|
Most understandable and helpfull
Thanks !! |
||
ConradCA
Optics GrassHopper Joined: May/24/2004 Location: United States Status: Offline Points: 9 |
Post Options
Thanks(0)
|
|
Chris
Everyone who hunts with a scope should read "Optics for the Hunter". It does a great job of explaining this stuff. You should consider carrying it for your customers.
You forgot to include the fact that there is a maximum usable exit pupil. The eye can only open so wide to except light. A young persons eyes can make use of at most 7mm. Middle aged eyes are about 5mm. This means that the effective exit pupil = min( max usable exit pupil,calculated exit pupil).
Conrad |
||
Chris Farris
TEAM SWFA - Admin swfa.com Joined: October/01/2003 Location: Texas Status: Offline Points: 8024 |
Post Options
Thanks(0)
|
|
You are correct. The school is in no way a complete lesson yet as it is a work in progress. It gets more added to it as we get time. Mr. Barsness' book relies too heavily on the old DEVA test. If you read the book and just ignore any sentence that has the word DEVA in it then its a wonderful read. We sell "Sporting Optics" by Wayne Van Zwoll.
|
||
kwoytek
Optics Professional Joined: September/06/2004 Location: United States Status: Offline Points: 5 |
Post Options
Thanks(0)
|
|
Chris, and Fans:
Kudos for your basic treatment of optical characteristics for riflescopes !! Please consider the text addition of typical eye pupil dilation that refers to hunting conditions (dawn to dusk in USA) that is nowhere near the pitch black (cloudy, moonless, starless, rural, and/or darkroom) conditions under which a young eye can open to 7mm. diameter and middle-age eyes can admit a maximum of 5mm. diameter shaft of light. Therefore, working scopes need only provide an exit pupil size of 4-5mm. diameter under normal conditions, and under 2mm. in bright noonday-sun target shooting instruments, unless a larger pupil is desired for jump-shooting, quick access sight pictures.
The objective clear aperture must also be chosen to avoid diffraction limited resolution constraints, wherein high magnification scopes suffer "empty maginifcation" when squeezed through a smaller than ideal objective lens designed to maintain a low profile on the rifle for stance comfort.
A short treatment of boresighting theories would be of benefit to most marksmen. Coarse alignment of scope to bore with mount adjustments is invaluable to conserving the internal adjustments for fine-tuning, and wind or range compensations, only. In this way, the common problem of "running out of adjustment" is minimized, and the mechanical axiom is preserved (that everybody forgets); when decentering any optical components in the path degrades the image quality, and sometimes the adjustments at the end of their travel have "dead" clicks, or may have a windage implication for extreme elevation corrections.
Any questions, please sound off? Ken
|
||
Chris Farris
TEAM SWFA - Admin swfa.com Joined: October/01/2003 Location: Texas Status: Offline Points: 8024 |
Post Options
Thanks(0)
|
|
Ken,
Very good information, thanks for it. I like to have a larger than necessary exit pupil for the exact reason you cite.
I have heard that as long as you are in the center 20% of the scope's adjustment range you should be OK. What do consider an acceptable amount for adjustment? The erector tubes desire to follow a curving path when adjustments are bottomed out can be solved by using a square saddle assembly but you will still have problems if you have adjusted your scope this far as spring tension is not equal on all sides. What do you know about the advantages of a coil spring vs. a leaf spring to help prevent this problem? |
||
kwoytek
Optics Professional Joined: September/06/2004 Location: United States Status: Offline Points: 5 |
Post Options
Thanks(0)
|
|
Chris: There is no concrete rule, when it comes to acceptable deviation from the optical axis, since every optical design is different, even when the power ranges are identical in two different models. The amount of aberrations in each design dictates how much off-axis image can be used, and the rule of thumb is to minimize the offset in every way possible, then live with the consequences. In some scopes the astigmatism, color, Petzval curvature (cup-shaped image plane,) distortion, etc. will be apparent at 20% of full travel; in others (costly) there may be no noticeable degradation. Adjustment springs are best when not compressed enough to take a permanent set (plastic deformation.) Some beryllium copper and exotic alloy leaf springs are designed well enough to maintain elasticity, but it's generally easier and cheaper to find coil springs that will not go solid under full compression, expecially if they have a conical helix that collapses completely into itself. Hope that helps. Ken |
||
David Wood
Optics GrassHopper Joined: October/13/2005 Location: United States Status: Offline Points: 2 |
Post Options
Thanks(0)
|
|
Sorry for being new to your forum I wish I had known about it before I spent money unwisely. I would like to make a request of you that may not be doable but here goes.With all the scope choices Chinese, Japanese, European, USA, could you make a general comparison of manufacturing techniques and differences and what well known MFR's contract out scopes to other countries.The reason I am so perplexed is, I have: 2 BSA 36X (Japan) excellent but ordered 2 more same but China (junk) 2 BSA 6X24 (China) OK 3 Redfield 2ea 3X9 1ea 4X12 OK to pretty good 2 Leupold 1ea VX2 and 1ea VX3 that I consider Gold standard
This may be a Honda, Volkswagen, Cheverolet,comparison but you can buy any of these and expect to get 100,000 miles from each. Thanks David Wood |
||
David Wood
|
||
catt_tracker
Optics Apprentice Joined: January/14/2006 Location: United States Status: Offline Points: 103 |
Post Options
Thanks(0)
|
|
Thank you that helped clear things up.
|
||
giuseppe
Optics GrassHopper Joined: January/05/2006 Status: Offline Points: 16 |
Post Options
Thanks(0)
|
|
Dear Chris, Can I have your permission to translate this interesting article in the Italian Language and to put this article on two italian airgun forums? Thare are many italian airgun enthusiastics that cannot read the english language. Obviously I will write your name and the link to your forum on the article. And I will send you the link in the italian forums. Thank you Giuseppe Stama From Italy
P.S.: if you give me your permission, can you send me the pictures that I cannot see on this article? (magnification and reticles) Thanks again |
||
Chris Farris
TEAM SWFA - Admin swfa.com Joined: October/01/2003 Location: Texas Status: Offline Points: 8024 |
Post Options
Thanks(0)
|
|
Sure, use anything you want on O.T. I'll try to find those images and get them restored.
Chris |
||
medic52
Optics Professional Joined: October/05/2006 Location: Missouri Status: Offline Points: 893 |
Post Options
Thanks(0)
|
|
EXCEPTIONAL writing, Thank you for the time and effort, as being new to this board I have been brought from dark to light concerning scopes. It has help so much that I have purchased two new scopes from the recommendations and articles on this board.
|
||
"The true soldier fights not because he hates what is in front of him, but because he loves what is behind him." G.K. Chesterton
|
||
William Ronald
Optics GrassHopper Joined: October/25/2006 Location: United States Status: Offline Points: 1 |
Post Options
Thanks(0)
|
|
I gotta say that I am very happy to have found this site, after reading the post I have a feeling I will learn alot about scopes and exactly how to use them correctly! Thanks for taking the time to post this!
|
||
sebastian
Optics GrassHopper Joined: May/03/2007 Location: Indonesia Status: Offline Points: 2 |
Post Options
Thanks(0)
|
|
Hi, Just new to this forum, and find this thread very informative. ...Thanks so much for the poster for the great informations!
To understand more about the Leupold competition series, do you have a sectional drawing/photo just like the pic in the first page?
Many thanks in advance, sebastian in Indonesia.
|
||
Chris Farris
TEAM SWFA - Admin swfa.com Joined: October/01/2003 Location: Texas Status: Offline Points: 8024 |
Post Options
Thanks(0)
|
|
Sorry we do not have any cut away type pictures of the Leupold.
|
||
RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
Post Options
Thanks(0)
|
|
Hi, Sebastian, welcome to OT! Based on the fact you live in Indonesia and the fact you're inquiring about a Leupold comp scope, indicating you're probably a benchrest shooter, you wouldn't happen to be the same Sebastian who manufactures the excellent SEB coaxial front rest would you? If so, your rest is very nicely designed and built, my friend! If I didn't already have a good front rest I'm pleased with, I would have bought yours.
For those who are interested in a great coaxial (joystick) style front rifle rest for benchrest shooting, you owe it to yourself to check out the SEB rest:
http://www.sebcoax.com/default.asp
|
||
Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
||
Post Reply | Page 12> |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |