Loosing Image in Scope

J

Jeffreytooker

Guest
I shoot mostly Weaver T-36 scopes at distances frrom 50 to 300 Yds. Sometimes after shooting for twenty or so minutes the target image will get blurry and the cross hairs will still stand out sharply. If I quit looking through the scope for thirty seconds or a minute, when I look back in the scope things are normal for a few seconds. After that the target gets blurry again. I am 67 YO. I have worn glasses since I was 5 YO. I am a right handed person with left eye dominance and shoot left. Is this a scope problem or an eye problem?

I am building a 30 BR which is comming along nicely. I need to fix the vision problem to be able to shoot it reliably.

Thank you.

Jeffrey Tooker
 
Jeffrey,

Have you carried out these two steps necessary to see properly thru a rifle scope?

(1) Focussing the crosshairs: Loosen the lock ring on the scope eyepiece, point the scope at a clear blue sky or a white wall of a room & crank the eyepiece until the crosshairs are in sharp focus. With some scopes, the eyepiece movement is slowish, so try cranking it half a turn, look at the crosshairs, crank again & look again until you are sure that the crosshairs are as sharply focused as you can get them, then screw up the lock ring. One of my scopes has such a slow adjustment that I crank all the way thru until the crosshairs go out of focus, than come back again until they go out of focus the other way, then halve the number of turns made. Your brain can sometimes be too smart for its own good & adjust what you actually see to make it what you would like to see & the halving procedure avoids that.

(2) Focussing for the image: Your T36 has a parallax adjustment on the front bell, sometimes called a focus adjustment. You use that to bring the image you are looking at into sharp focus which usually (some Leupolds excepted) means that you have cut out parallax error with the scope & that you can move your eye around behind the scope without causing any optical circumstance to cause the lay of your aim to be off.

John
 
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John Kielly said:
Jeffrey,

Have you carried out these two steps necessary to see properly thru a rifle scope?

(1) Focussing the crosshairs: Loosen the lock ring on the scope eyepiece, point the scope at a clear blue sky or a white wall of a room & crank the eyepiece until the crosshairs are in sharp focus. With some scopes, the eyepiece movement is slowish, so try cranking it half a turn, look at the crosshairs, crank again & look again until you are sure that the crosshairs are as sharply focused as you can get them. One of my scopes has such a slow adjustment that I crank all the way thru until the crosshairs go out of focus, than come back again until they go out of focus the other way, then halve the number of turns made. Your brain can sometimes be too smart for its own good & adjust what you actually see to make it what you would like to see & the halving procedure avoids that.


John:

I have completed #2 previously. Have tried #1 before with same results as you. Will try the halving.

My gun is teal blue and green.

Thank you.

Jeffrey Tooker
Click to expand...
 
What's the weather like??

Jeffreytooker said:
I shoot mostly Weaver T-36 scopes at distances frrom 50 to 300 Yds. Sometimes after shooting for twenty or so minutes the target image will get blurry and the cross hairs will still stand out sharply. If I quit looking through the scope for thirty seconds or a minute, when I look back in the scope things are normal for a few seconds. After that the target gets blurry again. I am 67 YO. I have worn glasses since I was 5 YO. I am a right handed person with left eye dominance and shoot left. Is this a scope problem or an eye problem?

I am building a 30 BR which is comming along nicely. I need to fix the vision problem to be able to shoot it reliably.

Thank you.

Jeffrey Tooker
Click to expand...

If your scope is properly adjusted as the other two posters have advised, and it is still doing what you have described, it may be that you are experiencing the effects of heat waves off your barrel affecting the objective lens of your scope. This will make the reticule blurry and seem to float and change position. Naturally after a few moments when the barrel cools off the sight picture returns to normal. The fix for this is to attach a heat wave blocker on top of your barrel such as a piece of card board about two inches wide that runs from just under the front of your scope to within an inch of so from the end of the barrel. You can use Velcro for this. Also a suitable piece of window blind will do. This will prevent the heat waves off the barrel from affecting your sight picture. This is a common fix in the benchrest world.

Good luck...virg
 
[. Also a suitable piece of window blind will do. This will prevent the heat waves off the barrel from affecting your sight picture. This is a common fix in the benchrest world.

Good luck...virg[/QUOTE]

Virg:

Will try it.

Jeffrey Tooker
 
Jeffrey,

From your description of the problem, I think it is most likely that there is an offset between the plane of focus of your eyepiece and the plane of focus of the objective. For us older shooters (I'm 64) and particularly with fine cross hairs we tend to fixate on the cross hairs as our eyes become tired. Therefore, if there is a focal plane offset our visual system will try to fixate on the increasingly difficult to see cross hairs even at the cost of focus of the target image.

Also note that achieving proper eyepiece focus on the plane of the cross hairs is more difficult than commonly thought particularly for fine cross hairs which are difficult to resolve clearly. The process used needs to be very carefully and methodically done. For a series of comparison tests of scopes by multiple observers, the following setup protocol was found to work very well for all observers:

Eyepiece Focusing – Scope mounted and aimed at a blank diffuse target that fills the field of view (no features detectable within the field of view). Eyepiece set fully forward (toward objective).

1. Adjust eyepiece for best focus on reticule (e.g., cross hairs).
2. Close aiming eye for 3-5 seconds. (NOTE)
3. Repeat until eyepiece focus is clear and sharp when eye opens.

Parallax Adjusting – Scope mounted and aimed at test target at desired test range (e.g., 100 yards). Set the parallax adjust for a yardage slightly longer (e.g. 150 yards). NOTE – the intent is to set for zero parallax not for best target focus.

1. Observe the cross hair versus a reference mark on the target while moving eye very slightly left to right (or up and down).
2. If the cross hair appears to move relative to the reference mark on the target, adjust the parallax setting toward the test range slightly.
3. Repeat until there is no apparent motion of the cross hair versus the reference mark on the target.

NOTE: The purpose of this step is to let the eye lens relax. During the eye piece adjustments your visual system tends naturally to try to accommodate focus by altering the shape of the internal eye lens. It is very important that our eyepiece focus and parallax correction be optimum with the eye internal lens relaxed so that we do not have to put the eye lens muscles under stress to achieve a valid sight picture.
 
Fred

Fred Bohl said:
Jeffrey,

From your description of the problem, I think it is most likely that there is an offset between the plane of focus of your eyepiece and the plane of focus of the objective. .
Click to expand...


Sounds like a "Been There Done That" I will try your method.

Jeffrey Tooker
 
This probably not related to this post but thought I would throw this out there for general information. Some are mentioning that they wear glasses. I just learned that polycarbonate type glasses will cause havac on your shooting. You should use Trivex glass in your glass as they have a less distortion and better linear properties. I learned this from Ron Hoehn and Larry Scharnhorst. They both fought this problem. The Doctors will tell you others are fine but it just that the Doc's don't understand the precise nature of this game.

Hovis
 
scopes

Have some t36 weavers and leupolds. Have found out shooting with my tri-focial glasses have problems like you have. Now I take my glasses off and I can see better and clearer at 100-200 and out. Some times when write notes on my range books and go back to shooting and in one or two shots I realize I have my glasses on again and take them off and I can do better. This helps me, you may want to try it. Good Luck craig
 
Jeffreytooker said:
I shoot mostly Weaver T-36 scopes at distances frrom 50 to 300 Yds. Sometimes after shooting for twenty or so minutes the target image will get blurry and the cross hairs will still stand out sharply. If I quit looking through the scope for thirty seconds or a minute, when I look back in the scope things are normal for a few seconds. After that the target gets blurry again. I am 67 YO. I have worn glasses since I was 5 YO. I am a right handed person with left eye dominance and shoot left. Is this a scope problem or an eye problem?

I am building a 30 BR which is comming along nicely. I need to fix the vision problem to be able to shoot it reliably.

Thank you.

Jeffrey Tooker
Click to expand...


Could you explain what you mean by "blurry". If the crosshairs are still sharp I don't see how it can be a problem with your eyes. Try this test. When it's "blurrry" rotate your rifle (on the rest) 90 degrees about the axis of the bore. If the problem distortion from heat rising fron the barrel it should immediately clear up. The heat shields other mentioned here should help.

If the "blurry" is not just a small reduction in sharpness of the image caused by heat shimmer but an overall loss of contrast it could be moisture condensing on the objective lens or (less likely) on one of the internal optical surfaces before the reticle. That would casue the image to go "blurry" leaving the reticle sharp. I'd expect that only to happen if you're shooting in moist air in clear weather where the front of the scope has time to cool and drop below the local dew point. Dewing over and then clearing up can take place in a few seconds.

I can't tell if that's the problem just from the word "blurry", but it's a possible.

.
 
Jeffrey,
The problem my friend is our age! I have the exact same phenom with my eyes buried in a scope trying to get a good group. You are focusing on the cross hairs, as you should, and the target starts getting blurry. You have two choices: shoot through it if you already started your squeeze or back off for a minute and relax your eyes by looking at the sky or something non-distinct. Invariably, after the relax period you can get through another shot without the problem happening again. In a 5 shot group this will usually happen to me two times. No big deal, not much we can do about it. Those who have not had this happen will doubt what I am saying, but I have gone through everything that has been recommended to you and none of it has cured the problem. Hope this helps.
 
Hovis has part of the answer...polycarbonate is less precise...Trivex is better, but the old fashioned GLASS spectacles are the best. Problem is glass is thicker and heavier and also less protective. If plastic were as good, wouldn't the scope makers use it in their high dollar scopes? No...they use glass and we mess them up by using cheap plastic in our spectacles.
 
Louis Boyd said:
If the "blurry" is not just a small reduction in sharpness of the image caused by heat shimmer but an overall loss of contrast it could be moisture condensing on the objective lens or (less likely) on one of the internal optical surfaces before the reticle. That would casue the image to go "blurry" leaving the reticle sharp. I'd expect that only to happen if you're shooting in moist air in clear weather where the front of the scope has time to cool and drop below the local dew point. Dewing over and then clearing up can take place in a few seconds. I can't tell if that's the problem just from the word "blurry", but it's a possible..
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Louis, this seems to be a problem I have at my club range in St. Bernard Parish in SE Louisiana, just below New Orleans.

We normally have as much as 97 pct. humidity or even 100 pct. in SE La each morning. As the day progresses it drops, but sometimes not. The day will be clear but very humid. Plus our ranges faces due south (180 degs) and the sun is always in our eyes. This plays hell with our poa/poi.

Roy
 
Well I may as well add a little "doom and gloom". My vision was 25/20 in my shooting eye, I was having the same problem described, I went to an optometrist and he checked my eyes over and wanted to sell me a pair of glasses, I told him no on the the glasses but I would try contacts to see if they help. I tried 3 different prescriptions of contacts and some days there would be no problem and other days the problem would still be there.

At that point I decided that either the optometrist was not providing a solution or I had problems that he wasn't finding. I made an appointment with an opthamologist and it took him about 2 minutes to detect that I had a cataract starting to develop (I am 70 so I guess it shouldn't be a great surprise that I had one developing), he scheduled me in and put in an artifical lens and a month later everything was great again - my vision is now back to 20/20, no more fuzzy crosshairs and life is good.

You may want to consider having an eye check by an opthamologist just in case you have a similar problem developing. My problem developed so slowly that I did not realize how much it was affecting me until I had the new lens in place.

Has it helped my scores - No!
Can I see better and not have fuzzy crosshairs now - Yes!

Life is good!!!

drover
 
It happened to me......

I was looking through a Weaver target scope one time and right before my eye the parallax changed! If i would make the proper adjustment, it would take a small length of time to come back into adjustment or to catch up. It seemed to me that something in "The Works" was gummed up. So I believe it could be the scope. It wasn't my scope or rifle so I never pursued the cause.
 
Jeffrey,

Maybe I missed it but I haven't seen this addressed..... do you shoot with both eyes open? I used to close one eye (I'm also cross-dominant) and found my situation to be like yours.

My fix was/is (with either eye) to shoot both eyes open and watch the conditions with only short lapses to the scope picture. I can now keep the target 'ready' with either eye while watching conditions and never find the blurring vision to be a problem. An exception occurred recently when I was straining to see 6mm bullet holes at 600yds, I'd inadvertently closed my off eye and the target started jumping in and out of focus. I opened the other eye, relaxed and the problem went away.

al
 
I was told when I got them that theres a very slight fish eye effect with these lenses, since they require more curvature to do the job.

I had noticed that I could shoot much better when I used my old heavy safety glasses. I then remembered that its always been suggested that you should try to look through the exact same portion of the lens everytime you shoot and that some shooters mark the lens of their shooting glasses or take a measurement and place an adhesive ring in the same spot on the lens to aim through.

When using a scope for serious business I adjust it so I can aim without my glasses, but backed off just enough that I can still aim with the glasses if in a hurry.

Also I've found that my eyesight has steadily improved after passing middle age, from very myopic to just a bit short sighted. The same process that makes a person with good vision farsighted as they get older can make a short sighted person's vision improve with age.

Also I remember from flight training many years ago that if you look at a point of light at night the light can become lost in the blind spot at the center of the retina. This blind spot can become larger as you get older, or due to degeneration or detachment of the retina.
It might be a good idea to have a examination of the inner eye. Might head off a condition before it becomes a real problem.

PS
I prefer a wooden handguard to cut heat waves, and besides my Milsurps I have handguards on some of my other rifles .
 
craig said:
Have some t36 weavers and leupolds. Have found out shooting with my tri-focial glasses have problems like you have. Now I take my glasses off and I can see better and clearer at 100-200 and out. Some times when write notes on my range books and go back to shooting and in one or two shots I realize I have my glasses on again and take them off and I can do better. This helps me, you may want to try it. Good Luck craig
Click to expand...

Craig,

I shoot with tri-focal glasses and use a Weaver T36. How much adjustment is there on the Weaver's eye piece as I have often thought of adjusting the scope to where I could shoot without glasses but thought I might un-screw the eye piece right off.

Best Regards,

Bill
 
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