Home Forums Hunting & Shooting Hunting Optics Parallax and Focus Problems at 300+ yards

Hi,

I’m trying to help a friend out, and hunting starts in a week. He has a Tasco world class plus 3 – 9 x 44, on a 700 ADL (270 win). He was checking to see if was still sighted in, a little concerned about his stepdad being the last one to use it.

What’s going on is that it’s not in very focus out past 150 yards, even 100 yards is a little fuzzy. I grabbed it, took it home, and looked through it out the pasture behind my house. Looking at a detailed object at 375, it’s indeed blurry, but it also seems like the parallax is pretty bad looking at that object. I would say it’s fuzzy enough that you might not be able to see the antlers very well, but you’d be able to see enough to hit him in the right spot ( at that range).

I even took a comparable power (and my best scope in that power range) a Toric ultra HD, and there’s a noticeable difference with clarity and parallax

What to do? Is this scope toast? The rifle date codes to 1971, and my guess is that this Japanese made scope is the original.

Thanks in advance.

Trash it and buy one of mine.
Money back guar-an-tee.

https://www.24hourcampfire.com/ubbt...s/17651387/rifle-scopes-f-s#Post17651387

Well, there are some guys that love those old Tasco's. I am not one of them. Your thread reminds me of a scope my buddy was recently having issues with. It was on his uncle's Thompson Center 22-250. That old Tasco was horrible to look through. He asked me what I'd put in it. Since it was his uncle's rifle he didn't want to spend a lot of money. I said just put a Burris FFII 3-9x40 with ballistic plex reticle on the rifle. He ordered one through Amazon for $109. When the scope arrived he asked if I'd help him mount it on the rifle and sight it in. We did that and then took it over to the 400 yard range. My buddy is wanting to use this as a yote rifle for his sons. The rifle shoots damn well and he's easily hitting small targets at 400 yards with the rifle. He couldn't be more happy with the rifle and his uncle is also happy with the choice. Win win right there.

NTG,
Did you go back and start from scratch? Set the parallax to Infinite and look at sky. Adjust the ocular until instantly clear when you look after looking away often.

You might need to adjust it slightly on something 300 yards away.

Ring man, it’s a fixed parallax scope. So I can’t adjust it. It’s interesting but you have to be about 5 to 6 power before it’s clear focus at those distances. Crank it past 6 power towards 9, and it gets blurrier as you go.

Start at the start. With the scope on the lowest power, loosen the occular lock ring and turn the occular all the way in. Now, take a piece of white paper and tape it tightly over the objective end. Quickly glance through the scope at the reticle, then take your eye away. Adjust the occular out a half turn at a time and repeat until the reticle is sharp and distinct. Then lock the occular lock down tight.

At this point, the reticle will be focused for your eye. Not everyone's eye...your eye. At this point it should stay sharp and focused no matter what the yardage. Lacking a parallax adjustment, that's about all you can do.

Hope this helps. -Al

Al- with parallax adjustability, does it matter what it's set at while initially focusing the reticle? Thank you.

Using white paper over the objective, I turn the parallax to the shortest yardage. -Al

As you have discovered, the problem is with the fixed focus. It is further compounded by the fact the objective lens is quite large for the focal length. This makes the F-number quite small, so the depth of field is reduced pared to say a 40mm or 36mm objective. When you crank in the magnification the CoC in the DOF becomes even more critical and the image is blurry. These scopes are usually focused at 100 or 125 yards. But if you say it's blurry at 100 yards, then you have to find out at which distance the scope is currently focused.

If the eyepiece diopter is set correctly and the reticle is crisp, then you need to figure out the focus distance. Got outside and aim at different distances until you can find the proper distance of focus.

Since you do not have an adjustable objective (ring at the front) or a side focus (what people mistakenly call a parallax adjustment,) you can try to change the base focus or, much easier, increase the DOF of the scope by changing the F-number of the scope. A simple way to do that is to get a slip-on objective lens cover and cut a hole in it. To reduce the f-number by 1 f/stop, I would suggest you drill a hole with a radius of 15mm. The hole will be about 1.25 inches in diameter. Make sure you do not drill the cover while it's on the riflescope.

When it gets dark, you can simply remove the drilled cover and regain the hole 44mm objective.

So, if side focus is not an adjustment for parallax, then just exactly IS it for?

It for adjusting the focus of the objective onto the first focal plane. Parallax adjustment is a by-product. When you have a clear, sharp, focused picture of your target, there is no parallax issue.

If it was solely a parallax adjustment device, it would actually move the reticle back and forth intersect with the focus of the image.

So, when I read about folks who "adjust the parallax down to 10 yards," they don't grasp that they are actually focusing the image from the objective so they can actually see the target. It's exactly like focusing a camera lens or a spotting scope and so on. You don't eliminate the parallax focusing a spotting scope or a camera lens, you are focusing the lens to get a clear, crisp image.

In the present case being discussed here, I was just looking for a way for the user to have a clearer picture by extending the depth of field and trying to keep the CoC small enough to have usable image. Since the image will not be focused properly, parallax will be an issue and the best way to deal with that is to be as perfectly behind the rifle as possible. But for anything under 3-400 yards, parallax error won't be much. This is not a target or match rifle setup.

It does not matter which focal plane the reticle is in. The ocular is focused to the plane of the reticle and the objective is adjusted to focus the image of the target in that same plane---which ever one it is---by either the side focus mechanism or what is commonly referred to as the "adjustable objective" on the objective bell. There is no difference.

There is a lot of good info here, but the pick of it is to bin that scope

And by the way it is easy to adjust distance focus on that or any other fixed focus scope, simply screw the objective lens cluster in or out using a 2 pronged tool