blur in middle of eyepiece (2 Viewers)

[puprescue]

am a fairly new member and this will be one of my first posts. i have several eyepieces for Fieldscope ED 60 and 82....these are old scopes, the 60 was bought in the 1990's i think. the eyepieces are blured in the middle. top and bottom of eyepieces are fine. please tell me what the problem is and can it be repaired at a reasonable price? one eyepiece is variable and other is a 38X

 

[henry link]

That's pretty unusual. The oddest thing about it is that you are seeing the same thing through two different eyepieces (and presumably when they are mounted on either scope body). We have to try to come up with something that would affect both eyepieces and/or both scope bodies. I would start by checking to be certain there isn't some combination of scope and eyepiece that is free of the center field blurring. Next try unscrewing the eyepieces on each scope 1/4 turn and see if the unblurred top and bottom shifts to the sides. If not, retighten the eyepieces and rotate the scope bodies 1/4 turn and look for the same thing. Does the blurring look the same throughout the zoom eyepiece's magnification range?

A tilted element might explain what you see, but how likely is it that would happen to two eyepieces or two scope bodies? Sometimes people over clean the external glass of the eyepiece creating a spot of tiny scratches concentrated near the center of the lens surface. Conversely, smudges on dirty external glass at either end of the eyepiece could have a similar effect to scratches causing blurring of the the field center more than the edges. Closely examine the external glass surfaces for scratches or smudges. Also look through the objective end of the scopes with bright light coming through the eyepiece end and look for any sign of film, smudges or scratches on lens surfaces.

Meanwhile I'll try to think of some other possible explanations.

 

[Binastro]

I couldn't think of a simple explanation.

Could it be the eyes and a central fault?
At least try both eyes to see if the same occurs.
Are glasses being worn?
Are the glasses old if being used?

Do the scopes have an optical window at the back near the eyepiece?

Regards,
B.

 

[puprescue]

Henry, will try your suggestions tomorrow. i will rule out scratches as i'm one who doesn't clean optics often. i ruined a good pair of binos many years ago by over cleaning. didn't mention that scopes [with eyepieces] were sent to Cory Suddarth to be cleaned [problem existed before being sent] was disappointed that view hadn't changed after cleaning. Cory does good work.

Binastro, i do not wear glasses while using scopes or binos [problem does not exist with any of my binoculars]. you may be onto something regarding eye problems however. i'm 83 in a few months and eyes are not perfect, though i only wear reading glasses. can spot a mule deer or coyote standing in sage brush at 200 yards.

will spend time tomorrow trying suggestions and post some observations [no pun intended] tomorrow night.

 

[puprescue]

am going to have to wait til tomorrow to report, as i had some un-forseen events arise today.

 

[jring]

Hi,

following up on Henry's brilliant idea to unscrew the EP a quarter turn to rule out the EP and rotate the whole scope, the same could be done with the observer...

No, I'm not asking you to unscrew your head or eye a quarter turn but just to look through the scope while standing beside it... that way your eye is rotated a quarter turn or thereabouts as compared to normal use and if the eye is the problem, the blurring should now be a vertical stripe in the middle while left and right rare fine.

Joachim

 

[puprescue]

we had a blue bird day today so i spent time looking through my scopes, changing out eyepieces from time to time. turning the eyepiece a quarter turn, or rotating the scope 90 degrees did not change the blurry spot. with the zoom lens the view became better as i dialed down the magnification. i tried both eyes......no difference. did not try standing beside the scope as suggested by jring. what does this suggest?

the view through these scopes/eyepieces is very good, despite the mid blurry section. you scope perfectionists would not be satisfied with view i see, however. am open to your interpretations.

 

[kabsetz]

Especially considering you age and how you report that with the zoom the central blurring reduced when you dialled magnification down, I'd suggest that it is your eyes. Possibly cataracts. The scopes have smaller exit pupils than most binoculars, and the exit pupil gets smaller as you increase magnification. If your eyes have problems in the center of you pupils, they will show more the smaller the exit pupil of the optics.

I had to switch the eye I use with a scope a few years back when I noticed reduced image contrast and sharpness in my dominant and heretofore better left eye. At first, it only showed at magnifications that resulted in exit pupils of some 1,5 millimetres or less, but has gotten somewhat worse by time.

- Kimmo

 

[henry link]

I was going to suggest exactly the same thing as Kimmo, provided you haven't already had cataract surgery. Whatever the exact problem turns out to be I think your observations yesterday virtually eliminate the optics of the scopes as the cause.

Henry

 

[puprescue]

my eye Dr. several years ago told me i'm a year or two away from cataract surgery. a younger brother just had the surgery and has noticed much better vision. i appreciate all of your comments and suggestions. will report back after surgery.

thank you all again