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  1. #1
    Join Date
    May 2005
    Location
    Newton ,Massachusetts
    Posts
    500

    Question Red Dot Sight Zeroing

    I recently purchased Photosolve’s Xtend-a-Sight and a Daisy Electric Point Sight # 7809 (Red Dot). My problem is with zeroing the sight. I zeroed at about15 feet per the instructions with the Daisy. It works well at about15 feet, but not at greater distances.

    A great many years ago, when I was in the Army, we zeroed our weapons at various distances, such as 100 yards, 200 yards, 500 yards. We also had a setting the I believe was called Battle Field Sight. The sight had a thumb wheel which we could start a zero and count the clicks the desired setting. The Daisy uses a Phillips screwdriver and does not have a starting point.
    Changing settings in the field is not practical.

    It would seem that I need to zero at a distance that will work at most distances I might encounter (Battle Field Sight). I was wondering what other who are using Red Dot Sights are doing?
    Last edited by JLV; 06-15-2006 at 10:31 AM.
    Panasonic FZ20, Kodak DC4800, Canon SD850 for when I don't want to carry a camera
    http://JLVACCARO.4T.COM

  2. #2
    Join Date
    Apr 2006
    Location
    Exeter, UK
    Posts
    883
    I think that sighting a camera is a bit different to sighting a projectile weapon.

    First, there is no "bullet drop".

    Second, with the weapon, you're concerned with absolute accuracy - x inches, at whatever range you zero at. With a camera, you're only concerned with angular accuracy - 6 inches parralax error at your minimum focus distance, say a couple of feet, is a lot. 6 inches at a hundred yards is unnoticeable.

    So you need to sight in so that you're not too far off at the closest range you're interested in, and as loong as that isn't too far off parallel to the lens axis, you'll be OK.

    If you've got a 10x zoom, then you probably want the error to be less that a tenth of the field of view, so you want the parallax convergence to be no more than 1 in 100. So you want to zero the sight for a distance 100 times the offset of the sight mounting from the lens axis.

    Zeroing at 15 feet would only work if the sight is 1.8 inches or less from the axis of the lens.

  3. #3
    Join Date
    Jul 2004
    Location
    Los Altos, CA
    Posts
    2,635

    Thumbs up Alex is right...

    But sometimes you may need a shorter "zero," as for example, when shooting hummingbirds in flight, where 10-15 feet is a typical distance. So you need to stay flexible. I have a low-parallax setup for my TZ1, which puts the axis of the Daisy sight about 1.5" from the lens axis. So, it works pretty well at almost any distance.
    Let a be your umbrella!

  4. #4
    Join Date
    May 2005
    Location
    Newton ,Massachusetts
    Posts
    500
    With my FZ20 the flash shoe is on top of the camera. The distance from the center of the sight to the center of the lens is about 3 1/2 inches. The zoom is 12 times.

    Thank you for your replies. Any additional info would also be appreciated.
    Panasonic FZ20, Kodak DC4800, Canon SD850 for when I don't want to carry a camera
    http://JLVACCARO.4T.COM

  5. #5
    Join Date
    Apr 2006
    Location
    Exeter, UK
    Posts
    883
    Thanks John!

    Quote Originally Posted by JLV
    With my FZ20 the flash shoe is on top of the camera. The distance from the center of the sight to the center of the lens is about 3 1/2 inches. The zoom is 12 times.
    OK, your "infinity zero" (I guess what you call battlefield sight) will be at 12 x 10 x 3.5" = 35 feet. That will put the dot within a tenth of the field of view at any distance beyond that.

    The near point is a bit trickier, and depends on what zoom you're using, but for full zoom, it'll be roughly 31' 10". (if I've got the sums right ) At wider angles it'll be a bit closer.

    If you expect to be shooting at closer ranges, you'll want to zero at the range you're expecting, or learn to allow some lead in the right direction to compensate.

  6. #6
    Join Date
    May 2005
    Location
    Newton ,Massachusetts
    Posts
    500
    Thank you for the additional information. I will give it a try.
    Panasonic FZ20, Kodak DC4800, Canon SD850 for when I don't want to carry a camera
    http://JLVACCARO.4T.COM

  7. #7
    Join Date
    Jul 2005
    Location
    Stockholm, Sweden
    Posts
    16
    I have my RDS mounted below the camera, almost as close to the lens axis as possible. And when it comes to zeroing, I always settle for infinity. That way, I know I have to aim 2" below my target if I want to get it centered at any distance. For me, no kind of sight is useful at short distances anyway since the local birds tend to move too fast when they are that close to me.
    /SimonG (My gallery)
    FZ20+uv+polarizer+homebuilt wired remote+RS232 remote+RDS; GIMP for all editing.

  8. #8
    Join Date
    Jul 2004
    Location
    Los Altos, CA
    Posts
    2,635

    Frankly, I only set it once...

    Quote Originally Posted by AlexMonro
    Thanks John!



    OK, your "infinity zero" (I guess what you call battlefield sight) will be at 12 x 10 x 3.5" = 35 feet. That will put the dot within a tenth of the field of view at any distance beyond that.

    The near point is a bit trickier, and depends on what zoom you're using, but for full zoom, it'll be roughly 31' 10". (if I've got the sums right ) At wider angles it'll be a bit closer.

    If you expect to be shooting at closer ranges, you'll want to zero at the range you're expecting, or learn to allow some lead in the right direction to compensate.
    And ever since, it's been just fine at the distances I'm used to using. As long as my bird is bigger than my 1.5" space, I figure the red dot is pointing close enough to the lens spot. Most often, my sighting is pretty good. Here, check out this sequence I posted today on dpreview.
    Let a be your umbrella!

  9. #9
    Join Date
    Apr 2006
    Posts
    242

    Calibrate at ~100' as you'll...

    probably have KFC (wanted whole chicken but got parts...) images if still at full zoom and subject is closer. At least that's worked for me pretty good. A lot also will depend on the subject's size/distance. I shoot mostly larger raptors and its hard to get closer than 100'

    If you're shooting Hummers and small moving subjects, estimate the average distance you're able to get to the majority of opportunities and collimate at that distance... as Alex/John have indicated.
    Telecorder [Dave]
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