Well, they're here. (1 Viewer)

Maljunulo · Aug 14, 2014

typo said:
Ed,

I suspect many stars are going to be bright enough to activate cones, so perhaps star gazing is more mesopic than scotopic. EdZ over on CN did a little star splitting survey a while back and came up with about 20/30 as a median result but with a big spread. So half as good as good as daytime acuity might be a reasonable generalisation.

From my experience I can readily confirm that real scotopic acuity can be as bad as you suggest and worryingly, it seems to be getting worse year by year. :-C

David

Are you guys telling me that scotopic vision cannot tell when a parallel bundle of on-axis rays, which fills the aperture, from a self-luminous, point source at infinity, is focused on the retina as a point by the optical train of a binocular?

I don't seem to have that trouble.

Richard

typo · Aug 14, 2014

Richard,

Betelgeuse has the biggest viewing angle of any star in the night sky at 0.054 arcseconds. Magnified 8x that would be 0.43" which is still a 100 times smaller than the smallest diameter spot resolvable by perfect photopic vision or 450x smaller than the stargazing acuity EdZ came up with. Your eye just blurs the image to around 160000 times bigger area than it really is... if I did the math right.

David

Maljunulo · Aug 14, 2014

typo said:
Richard,

Betelgeuse has the biggest viewing angle of any star in the night sky at 0.054 arcseconds. Magnified 8x that would be 0.43" which is still a 100 times smaller than the smallest diameter spot resolvable by perfect photopic vision or 450x smaller than the stargazing acuity EdZ came up with. Your eye just blurs the image to around 160000 times bigger area than it really is... if I did the math right.

David

David;

I understand all that, but I am trying to respond to your statement, which I paraphrase as "You shouldn't use a star to set up your diopter wheel, because scotopic vision is much worse, and you will end up with a setting which will be different than your daytime/extended object setting will be."

Do you have a citation for that? I should like to read more on the subject.

Richard

elkcub · Aug 14, 2014

Maljunulo said:
David;

I understand all that, but I am trying to respond to your statement, which I paraphrase as "You shouldn't use a star to set up your diopter wheel, because scotopic vision is much worse, and you will end up with a setting which will be different than your daytime/extended object setting will be."

Do you have a citation for that? I should like to read more on the subject.

Richard

Hi Richard,

I don't have a reference, but it seems to me that you're the one who needs to present more evidence. What you said is that it's best to set the diopter for daylight, i.e., photopic, viewing when the eye is dark adapted for scotopic viewing and focused on a faint object that must be positioned 17˚ off-axis in order to be seen optimally. Why would you think that's the best procedure?

Ed

typo · Aug 14, 2014

Richard,

I don't think I can readily suggest anything outside the subscription literature that has addressed it in quite those terms but if you haven't seen it already Gijs had written a very good article on various aspects of vision. Figures 36 and 40 particularly relate to this.
http://www.houseofoutdoor.com/testr..._AND_CONTRAST_IN_BINOCULAR-IMAGES_highres.pdf

The increased levels of aberration with pupil dilation is very well known, as is the different aberration and spherical error between eyes. An eye doc will correct the errors for a specific light level which is variously standardised in different countries. It will be sub-optimal for other light levels. You might conceivably have a totally different prescription for astronomy than for birdwatching.

In my case there is normally about a 0.2-0.3d difference between stars and daylight, but the increased astigmatism in my right eye is quite noticeable at night.

Hope that helps,

David

Maljunulo · Aug 14, 2014

typo said:
Richard,

I don't think I can readily suggest anything outside the subscription literature that has addressed it in quite those terms but if you haven't seen it already Gijs had written a very good article on various aspects of vision. Figures 36 and 40 particularly relate to this.
http://www.houseofoutdoor.com/testr..._AND_CONTRAST_IN_BINOCULAR-IMAGES_highres.pdf

The increased levels of aberration with pupil dilation is very well known, as is the different aberration and spherical error between eyes. An eye doc will correct the errors for a specific light level which is variously standardised in different countries. It will be sub-optimal for other light levels. You might conceivably have a totally different prescription for astronomy than for birdwatching.

In my case there is normally about a 0.2-0.3d difference between stars and daylight, but the increased astigmatism in my right eye is quite noticeable at night.

Hope that helps,

David

Is it relevant that I had my eyes "rebuilt" five years ago, due to cataract surgery, and I have only refractive errors (too small to correct with eyeglasses) and no astigmatism?

Also, are you saying that the two eyes "differ differently" between night and day, or have I confused myself?

I have been doing this for years, and it has worked every time ... maybe I'm just like the bumblebee, and don't know any better.|=)|

typo · Aug 14, 2014

Richard,

I haven't really looked into the post surgery variation, but of course it will do nothing for the corneal aberrations. I don't recall noting that the post op acuities were anything special. Do you know your results?

Yes I'm saying eyes can "differ differently" but may not in your case, I wouldn't know. I still suggest you should get more precise settings in bright conditions.

David

Maljunulo · Aug 14, 2014

typo said:
Richard,

I haven't really looked into the post surgery variation, but of course it will do nothing for the corneal aberrations. I don't recall noting that the post op acuities were anything special. Do you know your results?

Yes I'm saying eyes can "differ differently" but may not in your case, I wouldn't know. I still suggest you should get more precise settings in bright conditions.

David

Acuity, as in 20/20 both eyes postop? Currently 25/20, but I had laser capsulotomy on left eye, two or three years ago. The right one is better, but on the standard number/letter chart, they test the same. That's annoying, because I am left-eye dominant. No other significant aberrations, and no known corneal oddities. Ophth says I am way out on the end of the curve for my age, for both front and back of eyes. No retinopathy of any type.

I could see like a twelve-year-old postop, but the surgery was April and May of 2009, and I see changes, but ............

If there is a different way to express acuity, I don't know about it. Is there something like a lines per mm standard, or similar?

typo · Aug 14, 2014

Optical resolution is normally expressed in arcseconds. The convention is a little different in opthalmology which I'll skip for the moment, but 20/20 vision equates to 120 arcsecond optical resolution. A number here use line charts for binocular testing where lines/mm can be converted to arcseconds.

David

Maljunulo · Aug 14, 2014

typo said:
Optical resolution is normally expressed in arcseconds. The convention is a little different in opthalmology which I'll skip for the moment, but 20/20 vision equates to 120 arcsecond optical resolution. A number here use line charts for binocular testing where lines/mm can be converted to arcseconds.

David

David;

That is very interesting, as people make a really big deal over whether one can resolve e Lyrae with the naked eye. That is 208", so almost 3.5' which doesn't make it seem like much of a feat.

I had never heard the 120" = 20/20 before. Thank you for that little gem of knowledge.

Don't want to take any more of your evening.

Take care.
Richard

Tnx for the PM.

elkcub · Aug 15, 2014

Maljunulo said:
David;

That is very interesting, as people make a really big deal over whether one can resolve e Lyrae with the naked eye. That is 208", so almost 3.5' which doesn't make it seem like much of a feat.

I had never heard the 120" = 20/20 before. Thank you for that little gem of knowledge.

Don't want to take any more of your evening.

Take care.
Richard

Tnx for the PM.

Richard,

David is talking about daylight acuity, when the eye is light adapted and the target can be positioned on the fovea. However, visual acuity decreases linearly out to 30˚ from the fovea (see article). So, it's not surprising that the dark adapted eye would find it difficult to split e Lyrae, since it would be positioned about 17˚ off the visual axis for clarity.

Ed
PS. I really don't know if it makes a practical difference how one determines infinity focus, but I do resist the notion that using stars is necessary for the terrestrial viewer.

Maljunulo · Aug 15, 2014

elkcub said:
Richard,

David is talking about daylight acuity, when the eye is light adapted and the target can be positioned on the fovea. However, visual acuity decreases linearly out to 30˚ from the fovea (see article). So, it's not surprising that the dark adapted eye would find it difficult to split e Lyrae, since it would be positioned about 17˚ off the visual axis for clarity.

Ed
PS. I really don't know if it makes a practical difference how one determines infinity focus, but I do resist the notion that using stars is necessary for the terrestrial viewer.

Ed;

Thank you for a very interesting article, at least the parts that I understood.

You really have to try very hard not to learn as you go through life. I have become better informed, thanks to those who know what they are talking about, who responded to my posts.

I never said it was necessary ... I just thought that it would be better.

Richard

elkcub · Aug 15, 2014

Richard,

I enjoyed the discussion and hope that you continue with BirdForum.

Regards,
Ed

Maljunulo · Aug 23, 2014

To all who participated in this discussion:

I ran across this statement in a post by Steve C., in another thread.

"One thing I should mention, is this binocular seems to snap into perfect focus for me when I first do the standard, left eye with the focus, right eye with the diopter, then with both eyes open a little more diopter use and the focus really sharpens up best. Between last night and this morning I noticed a difference in needed settings. Last night I was using it to check out stars. I set the diopter for that purpose, and found I needed to readjust this morning scanning waterfowl on the lake. Other than that, the diopter seems to have no issues."

Richard

kabsetz · Aug 23, 2014

Richard,

At least for me, irrespective of which binocular I use, I need a different diopter setting for daytime and nighttime uses. My eyes change depending on the light levels. The difference is roughly half a diopter.

Kimmo

brocknroller · Aug 23, 2014

Same here, and with some fast focusing roofs, I also have to reset the diopter for different distances. Generally, I have less need to reset the diopter with Porros than with roofs.

I also noticed that IF EP bins that I could "set and forget" when I was younger, no longer focus for me over a wide range of distances. My eye lenses aren't as flexible as they used to be and neither is my body! I need to get out those old Jane Fonda workout tapes and start stretching again.
Brock

Maljunulo · Aug 23, 2014

brocknroller said:
Same here, and with some fast focusing roofs, I also have to reset the diopter for different distances. Generally, I have less need to reset the diopter with Porros than with roofs.

I also noticed that IF EP bins that I could "set and forget" when I was younger, no longer focus for me over a wide range of distances. My eye lenses aren't as flexible as they used to be and neither is my body! I need to get out those old Jane Fonda workout tapes and start stretching again.
Brock

My eye lenses aren't flexible at all, as they are implants.

brocknroller · Aug 24, 2014

Maljunulo said:
My eye lenses aren't flexible at all, as they are implants.

In that case, just enjoy the Jane Fonda tapes. :smoke:

Brock

denco@comcast.n · Aug 26, 2014

Maljunulo said:
My glasses were just delivered by FedEx two hours ago.

I had only been able to try them, and compare them indoors, so the first outdoor use was a revelation. I sat on a balcony, overlooking my back yard, and looked at everything in sight. Unbeknownst to me, there is a chipmunk living in a toppled over maple tree just at the edge of my woods. I had quite a nice view if him scratching his fleas, and scurrying around, while he was sitting in a very shaded area.

The images are absolutely breathtaking, with subtle coloring, shading, and textures, previously unseen in my faithful Nikon Venturer LX. (also 10X42) The focus wheel is different, and brand new, so I will have to get used to that.

The balance is fine, and the glasses come naturally to the eyes. I like the sticky rubber, but I don't know if it becomes less sticky with use. I still need to use a star to set up the diopter adjustment perfectly, but no hope of that for at least 48 hours.

These are my new "drag them everywhere" glasses, and I wouldn't trade them for anything, even after only a half-hour's use. It is interesting to see what you never knew was there, when using other glasses.

(I have spent more than sixty years looking through various and sundry binoculars, and these are the best yet, by far.)

I also posted this as a customer review on the vendor's website.

Just two questions. Are the Zeiss 8x42 SF better glass than the Swarovski 8x32 SV's and should I trade my Swaro's in on them.

proudpapa56 · Aug 26, 2014

That was 2 questions.

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