I got a question from Jan Tollenaar of Canada via email regarding how far out should a sight’s extension bar be extended. The question was: “I am wondering if you or someone on your staff can tell (or advise) me what is the proper distance to set the extension bar on a target sight. I have not been able to find any reference for setting a proper distance. When you take a look at Axcel sight instructions there is a reference to most archers set the scope 30 inches from their anchor point. (Why 30 inches?) I heard a coach use a rifle analogy: setting the distance on the sight extension bar to its maximum is like a rifle with more distance between front and rear sights (better for long distances). Does distance between the archer and the target have bearing? (indoor at 18 vs. outdoor at 50 m). Or is it personal preference.”
This is a good question and things can be complicated, but the simple answer is you can put it anywhere.
The more complex answer is that there are a number of parameters involved as to what you best sight extension might be. Now, I wasn’t told whether we were talking about an Olympic Recurve target sight, a Compound sight with ’Scope, or a Pin sight, so I will have to include a number of parameters that might not affect you.
Here are the parameters:
1. The farther out the sight bar is extended, the farther apart your sight marks are. At longer distances, your aperture can get in the way of your arrow. At shorter distances you may see some interference with your sight line by your riser (if the riser is short). Youths trying to “make distance” often move their sight bar closer to the riser, even inside of the riser to benefit from these tendencies.
2. The farther out the sight bar (and aperture), the more sensitive the sight is and the more fine you can aim. (This is the rifle sights argument.) In opposition to this is that the farther out you hold it, there harder it is to hold it steady.
3. If you shoot with a peep sight, the aperture may be moved in and out to make your peep hole concentric with your scope housing.
4. With telescopic sights, it gets complicated. While these apertures are sold by the power (4X, 6X, etc.) the actual magnification is a function of the distance from peep to lens (the greater the separation, the greater the power).
5. The farther out the sight bar, the more forward heavy your bow will be (which is why you will see some designs have the sight bar at the bow with a long (and lightweight) carbon fiber boom out to the aperture.
This resulted in a follow-up question: “I’m not quite sure I understand: ‘the aperture may be moved in and out to make your peep hole concentric with your scope housing.’ Did you mean the scope can be moved in and out to make the aperture concentric with the scope housing?”
Yep, you got it in “one,” Jan! One aspect of exact aiming (that compound letoff affords an archer the time to do) is the alignment of the circular peep opening with the circular scope housing (see photo). You want the appearance of a little gap between the two, not so fine that one would fidget trying to get them perfectly aligned, but no so large a gap that you can’t easily see the two openings are concentric.
Moving the extension bar in or out a tad can fine tune this. If you have to move it a lot, you have the wrong hole diameter in the peep. (Generally hunters and indoor shooters shoot fairly large peeps (due to low light conditions), whereas outdoor archers shoot smaller peeps (to cut down the amount of light and also by selecting a smaller part of the cornea to focus the light through, it actually corrects one’s vision. (I have heavy astigmatism—so heavy I can’t get contact lenses—but I can shoot without glasses because of this effect. Optometrists are quite aware of this “pinhole effect.”)
As always, you want to move the bow, not the head to achieve this alignment (assume one’s head position is good ;o).
PS If just one bow is being used indoors and out, I think it is Specialty Archery which makes a peep with removable aperture holes and a variety of peephole insert sizes to choose from. This makes changing around from indoor to outdoor a matter of just changing peep height and peep opening and she is good to go on to the next season.