Used ED82 (1 Viewer)

[Astroguy2000]

After being impressed by my used ED50 I found and bought a mint ED82 with 25-75x zoom eyepiece for a great price.

It is in great condition and looks hardly used, only thing I'm finding is that the image doesn't look as bright as my ED50 (both on lowest mag 13x,25x and highest 40x,75x)
Thought that it would be brighter or be similar to the ED50.

Anyone have any thoughts on this ?

Thanks

 

[Binastro]

Maybe internal condensation, perhaps on the eyepiece/body connection.

Shine a torch into the front, or look into the front with a 60 watt bulb behind.

Possibly also balsam failure?

Regards,
B.

 

[Astroguy2000]

Maybe internal condensation, perhaps on the eyepiece/body connection.

Shine a torch into the front, or look into the front with a 60 watt bulb behind.

Possibly also balsam failure?

Regards,
B.

Shone a torch inside and through eyepiece hole, all looks clear inside.
It's ok up to around 60x, gets dark and loses sharpness at 75x.
Maybe I have a really good ED50 and slightly off ED82 as with same zoom eyepiece my ED50 is pin sharp all the way to max zoom.

 

[Binastro]

It is good it is clean inside.

Maybe a good example should be sharp at 75x.

Is the out of focus star image good, circular and central?

Regards,
B.

 

[Hermann]

It is in great condition and looks hardly used, only thing I'm finding is that the image doesn't look as bright as my ED50 (both on lowest mag 13x,25x and highest 40x,75x)
Thought that it would be brighter or be similar to the ED50.

It should be brighter at the same magnifications. Don't compare 13x (on the ED50) with 25x (on the ED82). You can get all sorts of funny effects if you do a comparison at different magnifications. Do a comparison at 25x on the ED82 and the ED50, i.e. you set the magnification of the zoom to slightly below 50x.

Shone a torch inside and through eyepiece hole, all looks clear inside.
It's ok up to around 60x, gets dark and loses sharpness at 75x.

That doesn't sound right. A good ED82 should have a pin sharp image at 75 provided the atmospheric conditions are good enough. In my neck of the woods they are usually best a couple of hours before sunset. That the ED82 gets darker at high magnifications is normal due to the smaller exit pupil.

Maybe I have a really good ED50 and slightly off ED82 as with same zoom eyepiece my ED50 is pin sharp all the way to max zoom.

I've got all three Nikon Fieldscopes (50mm 60mm and 82mm), and they're all sharp to their maximum magnification.

Hermann

 

[Astroguy2000]

It should be brighter at the same magnifications. Don't compare 13x (on the ED50) with 25x (on the ED82). You can get all sorts of funny effects if you do a comparison at different magnifications. Do a comparison at 25x on the ED82 and the ED50, i.e. you set the magnification of the zoom to slightly below 50x.

That doesn't sound right. A good ED82 should have a pin sharp image at 75 provided the atmospheric conditions are good enough. In my neck of the woods they are usually best a couple of hours before sunset. That the ED82 gets darker at high magnifications is normal due to the smaller exit pupil.

I've got all three Nikon Fieldscopes (50mm 60mm and 82mm), and they're all sharp to their maximum magnification.

Hermann

Ok, compared brightness at similar magnifications and the ED82 is noticeably brighter with similar/slightly better sharpness than my ED50.

Still not getting great sharpness at 75x even on 50m distance targets.

 

[Hermann]

Ok, compared brightness at similar magnifications and the ED82 is noticeably brighter with similar/slightly better sharpness than my ED50.

OK, that sounds better.

Still not getting great sharpness at 75x even on 50m distance targets.

Well, it's hard to say without looking at the scope. But maybe you expect too much? At 75x on the ED82 you need some very solid support, i.e. a rock solid tripod and head. And you need to make make sure you yourself don't "shake" too much if there's any wind at all. For such comparisons it's usually best to use a short tripod and sit on a decent chair.

In addition, the exit pupil on the ED82 at 75x magnification is only ~1.1mm. That's not much, especially in terrestrial observations, and unless you've got some practice using such small exit pupils you may get the impression the scope isn't "sharp". The ED82 is also not that easy to focus at very high magnifications. The ED50 with its focusing knob is much easier to focus at high magnifications.

Hermann

 

[Binastro]

There may also be temperature effects because of the tube and because of local atmospheric conditions.

Also ground level observations may be non optimal.

Don't observe over concrete or asphalt or buildings.

Regards,
B.

 

[jring]

Hi,

I would strongly recommend a star test - either on a cool overcast day with an artificial star at 30m or so or before sunrise during a clear night. In both cases the scope should have been outside for a few hours to cool down to ambient temperature.

Joachim

 

[Astroguy2000]

Done a quick star test and I can get 2 or 3 symmetrical rings away from.infinity.
Towards infinity best I can get is a fuzzy blob with no discernable rings.

ED50 star test has 2 to 3 easily distinguishable rings at both ends of out of focus.

 

[jring]

Hi,

so some overcorrection seems to be present. I assume the star test was with a real star from the time, so SA introduced by too close artificial star is out (the ED50 might still fare ok with an artificial star at the same distance). This link shows lambda/4 (barely diffraction limited) and lambda/8 (quite good) doffraction patterns - what does your ED82 look like?

Star testing telescope optical quality

The basics of star testing telescope: diameter of artificial star, distance induced spherical aberration.

www.telescope-optics.net

Joachim

 

[Astroguy2000]

Hard to tell exactly which diffraction pattern I have.

 

[kabsetz]

For the scope to be good, you should get discernible rings on both sides of focus, a fuzzy blob with no discernible rings on one side while the other side shows rings clearly is not good. A good 82 should also be very clearly superior to a 50 at high magnifications. I'm afraid your 82 is a lemon.

- Kimmo

 

[Astroguy2000]

For the scope to be good, you should get discernible rings on both sides of focus, a fuzzy blob with no discernible rings on one side while the other side shows rings clearly is not good. A good 82 should also be very clearly superior to a 50 at high magnifications. I'm afraid your 82 is a lemon.

- Kimmo

Shame as reading through the forums here it seems Nikon ED82's are very good for sample variation.
The image is brighter and superior at similar mags compared to my ED50 which I believe to be very good.
It's just at 60-75x where the image starts to soften.

I have also tried using the MCii zoom eyepiece from my ED50 to eliminate that.

Reason i wanted the bigger ED82 is for long distance viewing, sea watching and Astronomy (ED82 is highly regarded on Cloudynights) with the higher magnifications available.

Image is still perfectly usable at higher mags but doesn't deliver the same level of sharpness wow factor that my ED50 has.

I will send it in to Nikon for inspection to see if they can find anything wrong with it.
Hoping they can do something with it to improve it (maybe something has been knocked out of alignment)

 

[Binastro]

If something has ben knocked out of alignment then it would show in the star images.

However, possibly the spacing of the elements might be incorrect, which could lead to softness.
I would ask Nikon to check this, as it may be something they don't normally look for.

If you have very good acuity the softness would be noticed more.

Personally, I would expect to be able to use it at 120x or more.

Regards,
B.

 

[Astroguy2000]

Had the below reply from Nikon.
I've asked them if they can check optical alignment and spacing of elements.

I am writing with the regards to the repair of your Nikon Fieldscope ED82A and Fieldscope eyepiece lens 20-60X MC2.

The technician has been unable to recreate the fault you reported and has found both pieces of equipment to be operating to Nikon working standards.

Do you have any further information I can pass on to the technician which may help them to find the faults?

Please note – if a fault is found with the Fieldscope ED82A and a repair is needed, we may not be able to repair it due to the product being obsolete.

Alternatively, please let me know if you would like the equipment to be returned to you unrepaired.

 

[Binastro]

The technician probably does not have the necessary skills to do star tests.

It may be someone has worked on the scope already.

The spacing may be incorrect, the objective elements may have rotated by themselves.
I have even had objective elements back to front.

Just because the technician can take apart and reassemble a telescope does not mean he or she is an optical expert.

I have sent lenses to factory lens repairers and they have not seen the faults I have seen.

With Vivitar, I sent them a lens with test photos pointing out the faults.
They put three identical lenses on their excellent test bench and sent me the best one as a replacement.
It was excellent.

It is up to you what you want done.
If the scope was current, they might have been able to send you a replacement.

Personally, I wouldn't waste too much time and accept that I have a poor telescope.
It can still give useful images at lower powers.

Or hope the next scope is better.

I have probably had about as many poor telescopes as good ones.

Regards,
B.

 

[Binastro]

It may be that the lens elements are at the poor end of the normal range, and the result is a poor example of this Nikon telescope.
This may be within Nikon's pass rate.

Actually, it would take a very skilled optician to optimise lens element spacing and it is doubtful any of the normal technicians for any make of telescope have this skill.

Taylor Hobson did have these skills, and Zeiss probably also, but for military optics, as it wouldn't be cost effective for consumer optics, unless there is a glaringly obvious fault.

I sent some aero lenses to our top U.K. optics repair firm, and although they managed to clean these very difficult lenses, they did chip one element.
But more importantly the resolution of these lenses was not up to the very high Wild standards.
I think the critical spacing was not achieved.
It may be that even Wild could not have achieved the resolution of newly made lenses.

Zeiss west cleaned my 15x60 binocular for no cost, but I immediately saw they had chipped an eyepiece element.
They correctly blackened this edge chip, and in actual use there is no sign of any image loss whatsoever.
The technician knew his stuff.

Regards,
B.

 

[BoldenEagle]

It seems that Fieldscopes generally have good reputation as regarding optical quality consistency. But in the end, someone will eventually have one of bad copies and be disappointed.

My first scope was also Nikon Fielscope ED 82A and when compared side by side with other scopes (including Zeiss 85FL, Kowa 823 etc.) in the field, it allways rather obviously seemed less sharp at higher magnification (60x). I then just assumed that Nikon Fieldscopes are like that but lately have realised that it was just a bad copy. But at the time I didn't know anything about optical aberrations and how to test them (I can't say I know much today but at least I'm able to quite surely detect coma, astigmatism and spherical aberrations and tell whether the sample is a lemon or good one, thanks to knowledge gain from other members here...) using a star test. It would be interesting to star test the sample but I don't have it anymore. The next scope I bought was Leica Apo Televid82, which had optical aberrations also (later revealed by star test) but it was still sharper than my Fieldscope when comparing side by side. I used the Leica about 7 years and I would say that even with some aberrations present, it was certainly able to serve well in the field. I now have quite good sample of Kowa 883 which is optically better than my Leica but the difference is not that huge and can mainly be seen in the higher end of the magnification range, especially when using teleconverters which both scopes have.

Regards, Juhani

 

[Astroguy2000]

Received the scope back from Nikon.
I will continue to use it as the viewing is still fine.