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#26 MT4

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Posted 15 September 2021 - 11:45 PM

Astigmatism in your eyes is different from astigmatism in the optics.

 

I have moderate levels of astigmatism in both eyes, -1.5 in my left eye and -0.75 in my right eye.  Without my glasses, any star would look like a bloated stone with quite a bit of spiking, and there'd be no such thing as a pinpoint star anywhere in the view, center or at the edge.

 

With my glasses on, stars look much cleaner but of course the downside is that I need quite a bit of usable eye relief, at least 14mm and 2-3mm more when I put my binoculars on a tripod.   An important thing to keep in mind about usable eye relief is that oftentimes a manufacturer may claim that eye relief is 18mm only for the usable eye relief to be just 13-14mm due to the ocular lenses being well recessed and/or extra bits of rubber in the eyecups wasting eye relief.  (On some of my binoculars, I've had to do some sort of eyecup "surgery" to maximize usable eye relief.)

 

Another way of dealing with astigmatism in your eyes is to get binoculars with a smaller exit pupil, i.e. higher mag for the same objective size.  As the exit pupil is reduced, there'll come a point where it's small enough to beat back the astigmatism in your eyes.   (For my eyes, that small exit pupil size is a bit over 1mm, which practically means that I must wear glasses for stargazing when using binoculars.)

 

Here's the site that I typically use when researching usable eye relief on binoculars of interest.   (The Pinac collection is chock full of good-quality/premium binoculars, so it might be a good starting point for you to look for options on good-quality optics.)

https://binocular.ch...ion/#collection


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#27 ihf

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Posted 16 September 2021 - 12:38 AM

Televue has a chart for the visibility of astigmatism. You could probably get away without glasses during the day. But that assumes taking off glasses to look through binos, which is impractical (where to store them?) So better get binos which are glasses friendly. Those have usually eye relief > 18mm.

 

DioptrixAstigmatismVis.gif



#28 ECP M42

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Posted 16 September 2021 - 08:35 AM

That is my astigmatism data.

Can you elaborate on what accepting this means for viewing without glasses for correction?
This seems like another reason to seriously look at contact lens.

The guys from CN have already investigated well, I just add a link on the subject. 

- https://en.wikipedia...ki/Astigmatism 

 

I'm not an expert, but I think 0.75 is a pretty obvious / compromising value. My eyes also tend to astigmatism (0.25) and with the reading corrective glasses I can see the starry sky more "point-like".
Contact lenses could be a great solution if your binoculars don't allow you to see the entire field of vision with glasses. And in some binoculars it is possible to install ad hoc corrective lenses, and opt for a different solution.


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#29 Jon Isaacs

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Posted 17 September 2021 - 01:42 PM

Traditional binoculars are not the right tool for observing the planets, which are all, even Venus at inferior conjunction and Jupiter, very small in apparent size.  Binoculars excel at producing larger fields of view than almost all telescopes can produce. 

 

There's a section on binocular observing towards the bottom of my post (#22) at https://www.cloudyni...mers/?p=5184287 that you may find useful, memheli.

 

:waytogo:

 

As Dave said, viewing the planets is best done with a telescope. Mars, Jupiter and Saturn can richly detailed but are best seen at magnifications of 200x or more.  If one wants to view the planets with 2 eyes, a binoviewer is best.

 

Jon


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#30 ihf

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Posted 17 September 2021 - 02:10 PM

To return to some concrete recommendations.

 

Fixed eyepiece binos will max out at 20-25x. There are good ones like Oberwerk 20x70, APM MS 20x80 ED, APM MS 25x100 ED. Cost is USD 500-1300. Without center focus they work well at infinity but not so good during the day close up. Anything over 10x will show you planets as a small colored disk, without detail. Detail on planets usually starts at 40x. Binos are designed to show low magnifications well with large pupils and rich colors. Similar for spotting scopes. The upper limit is disputed, but it tends to break down terrestrially over 40x and on the sky over 80x for various reasons. A telescope could go higher to say 200x, but show very little field and very black/white.

 

There are small 70mm 45 degree angled binoculars that some members carry in backpacks and use during the day at 40x and at night even a little higher mag. A Pentax PF65EDA is what I carry during the day when I want a lot of magnification. It allows using nice astronomy eyepieces like Morpheus. Spotting scopes are ridiculously easy to mount using a ballhead turned sideways and even a short tripod. (Can be short but at high mag not shaky.)

 

Any binoculars pointed straight up are tough to mount. You would need a good large tripod, elevator column and a solid video head. That can add USD 500-1000.

 

If you don't want to mount binos you could chose Canon image stabilized (IS) binos, say the popular 15x50. It is a lot of fun to cruise the sky with it. Canon also has IS models 10x42 (very nice optics and stable) and 18x50 (a bit shaky, but more like a hand held. Get a comfortable camping chair and cruise the skies.

 

A 15/18x50 would be best paired with something wide in the 8x32 range for the day. There are many good choices. I personally prefer even lower magnification but wider field of 10' at 6.5x32 (Kowa), as that also works well at night for me.

 

A big mounted bino (70+mm) would probably be better paired with a 8x42 or 10x42, as the latter would be used more often at night. Setting up a mount creates a lot of resistance, at least for me.


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#31 Fiske

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Posted 17 September 2021 - 02:53 PM

Televue has a chart for the visibility of astigmatism. You could probably get away without glasses during the day. But that assumes taking off glasses to look through binos, which is impractical (where to store them?) So better get binos which are glasses friendly. Those have usually eye relief > 18mm.

 

DioptrixAstigmatismVis.gif

This is an interesting table, and line of thought.

 

As to where to store glasses when looking through a binocular, that is easy. Shirt pocket, hang in shirt collar, set on Costco shelving unit that is doubling as a light shield, etc. wink.gif

 

I do find myself wearing glasses more often when observing with binoculars, particularly at lower magnification (ie larger exit pupils) which matches the chart. However, where glasses really become crucial is attempting to resolve closer or otherwise difficult double stars. At least of the objects I am currently observing. It's much less troublesome (at least for my astigmatism -- RT1.00/LT1.25) when roaming star fields and not attempting to resolve fine detail. Binocular vision seems to be enough in that activity to prevent the astigmatism from being annoying. Increased magnification not only reduces exit pupil, it also increases separation making double stars easier to resolve. I suspect that increasing the separation is a more important factor to me, in this regard, than reducing the effect of astigmatism, but I'm not sure how to test that.

 

Anyway, this issue directly impacts where I use instruments like the Nikon 7x50 and 10x70 SP binoculars. I can observe with them wearing glasses, but they are much less comfortable in that mode than with uncorrected vision. They are superlative for viewing star fields from dark sky sites, so I reserve them for that use. (And they are well worth it, IMO.) grin.gif

 

Fiske


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#32 Jon Isaacs

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Posted 17 September 2021 - 03:11 PM

This is an interesting table, and line of thought.

 

As to where to store glasses when looking through a binocular, that is easy. Shirt pocket, hang in shirt collar, set on Costco shelving unit that is doubling as a light shield, etc. wink.gif

 

I do find myself wearing glasses more often when observing with binoculars, particularly at lower magnification (ie larger exit pupils) which matches the chart. However, where glasses really become crucial is attempting to resolve closer or otherwise difficult double stars. At least of the objects I am currently observing. It's much less troublesome (at least for my astigmatism -- RT1.00/LT1.25) when roaming star fields and not attempting to resolve fine detail. Binocular vision seems to be enough in that activity to prevent the astigmatism from being annoying. Increased magnification not only reduces exit pupil, it also increases separation making double stars easier to resolve. I suspect that increasing the separation is a more important factor to me, in this regard, than reducing the effect of astigmatism, but I'm not sure how to test that.

 

Anyway, this issue directly impacts where I use instruments like the Nikon 7x50 and 10x70 SP binoculars. I can observe with them wearing glasses, but they are much less comfortable in that mode than with uncorrected vision. They are superlative for viewing star fields from dark sky sites, so I reserve them for that use. (And they are well worth it, IMO.) grin.gif

 

Fiske

 

Normally when observing close doubles, exit pupils are less than 1 mm, 25x/inch, very often they're less than 0.5 mm, 50x/inch.

 

The need for glasses when using binoculars is due to insufficient magnification more than anything, normally you'd just crank up the magnification and you would be well into the "eyesight astigmatism not visible" region.

 

Jon


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#33 MT4

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Posted 17 September 2021 - 06:08 PM

Normally when observing close doubles, exit pupils are less than 1 mm, 25x/inch, very often they're less than 0.5 mm, 50x/inch.

 

The need for glasses when using binoculars is due to insufficient magnification more than anything, normally you'd just crank up the magnification and you would be well into the "eyesight astigmatism not visible" region.

 

Jon

 

I can attest to this.

 

Using my 82mm Kowa Highlander at 50x with the exit pupil being 1.64mm, I've found that I still need my glasses to avoid the annoying effect of astigmatism (-1.5 in my left eye.)   When I put my Kasai 2x54 between my eyes and the 50x82 Kowa, the effective exit pupil is reduced to 0.82mm and voila there's no need to wear my glasses!   

That's the first time I ever saw pinpoint stars without needing to wear my glasses for astigmatism correction and it was liberating to say the least.


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#34 KennyJ

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Posted 18 September 2021 - 02:38 AM

Fiske,

 

One simple way to study the benefits of the extra magnification, per se vs the reduction of the effects of astigmatism when viewing double stars would be to compare the images unmasked and masked.

 

For example, make some 15mm masks for your 50mm binoculars and compare the images between 10x50 and 10x15.

 

Kenny


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#35 memheli

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Posted 19 September 2021 - 09:30 AM

I can attest to this.

 

Using my 82mm Kowa Highlander at 50x with the exit pupil being 1.64mm, I've found that I still need my glasses to avoid the annoying effect of astigmatism (-1.5 in my left eye.)   When I put my Kasai 2x54 between my eyes and the 50x82 Kowa, the effective exit pupil is reduced to 0.82mm and voila there's no need to wear my glasses!   

That's the first time I ever saw pinpoint stars without needing to wear my glasses for astigmatism correction and it was liberating to say the least.

well, I've never seen anything like a 2x54 until I just googled it and saw some made by Orion.  I'm struggling to keep up here with all the info being offered. Very cool indeed.


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#36 memheli

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Posted 19 September 2021 - 09:57 AM

Astigmatism in your eyes is different from astigmatism in the optics.

 

I have moderate levels of astigmatism in both eyes, -1.5 in my left eye and -0.75 in my right eye.  Without my glasses, any star would look like a bloated stone with quite a bit of spiking, and there'd be no such thing as a pinpoint star anywhere in the view, center or at the edge.

 

With my glasses on, stars look much cleaner but of course the downside is that I need quite a bit of usable eye relief, at least 14mm and 2-3mm more when I put my binoculars on a tripod.   An important thing to keep in mind about usable eye relief is that oftentimes a manufacturer may claim that eye relief is 18mm only for the usable eye relief to be just 13-14mm due to the ocular lenses being well recessed and/or extra bits of rubber in the eyecups wasting eye relief.  (On some of my binoculars, I've had to do some sort of eyecup "surgery" to maximize usable eye relief.)

 

Another way of dealing with astigmatism in your eyes is to get binoculars with a smaller exit pupil, i.e. higher mag for the same objective size.  As the exit pupil is reduced, there'll come a point where it's small enough to beat back the astigmatism in your eyes.   (For my eyes, that small exit pupil size is a bit over 1mm, which practically means that I must wear glasses for stargazing when using binoculars.)

 

Here's the site that I typically use when researching usable eye relief on binoculars of interest.   (The Pinac collection is chock full of good-quality/premium binoculars, so it might be a good starting point for you to look for options on good-quality optics.)

https://binocular.ch...ion/#collection

wow this Pinac collection site you reference is one for the "bookmarks'.   Thank you.


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#37 memheli

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Posted 19 September 2021 - 10:10 AM

Curious if anyone here is from the West TN area.  I'd love to meet up with someone that had a collection of Bino's I could look thru.  Will be going to Bass Pro and another shop next week to try a few out.  



#38 pat in los angeles basin

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Posted 19 September 2021 - 10:14 AM

One of Pinac's valuable contribution is to look at the eye relief that has has measured on each bino and how he achieved that figure and the eye relief as stated by the makers data. Sometimes they are the same- most of the time they are different. I don't think there is a standard as to where the measurements are taken.   Pat


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#39 Fiske

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Posted 19 September 2021 - 12:28 PM

Normally when observing close doubles, exit pupils are less than 1 mm, 25x/inch, very often they're less than 0.5 mm, 50x/inch.

 

The need for glasses when using binoculars is due to insufficient magnification more than anything, normally you'd just crank up the magnification and you would be well into the "eyesight astigmatism not visible" region.

 

Jon

With telescopes, yes. With binoculars increasing the magnification past some level requires a lot more effort/ingenuity than swapping eyepieces. As MT4, among others, has demonstrated. wink.gif

 

Last night I was observing STF 2816, a triple star close to the center of the IC 1396 cluster in Cepheus (near Herschel's Garnet star) that I have been spending considerable time with over the past week. (What Did You See post forthcoming.) I was messing around with the 82XL on the OB 5000 head swapped onto the carbon fiber elevator column on a TR3 tripod that previously held a NitroTech 608 head (which I expect will be finding a new home soon). Just a trial run with the 5000 head to see how well it works with the 82XL (okay -- a little stiff -- but preferable to the 608 for a lot less money, IMO). 

 

Anyway, I was using Pentax 20XW eyepieces, which is about 22.5x. 

 

This is my log entry from last Wednesday evening:

 

STF 2816 Cepheus
21h39m +57*29'
AD 5.73/7.53 20.6" pa 339*
AC 5.73/7.48 11.8" pa 121*
The C/D components are easily seen with the 100XL (10/7/5 XW). C was a challenge to resolve with the 82XL+20XW, but could just be seen. Astigmatism factor here. lol Easier with the 14XWs. The C/D stars are light blue and the primary is a warm white. This is a delightful triple.

 

Last night (Saturday evening 18 September) I decided to have a look wearing glasses, and the C component was easily seen and spectacular so close to the primary and far sharper than when viewed with my non-corrected vision. Yes, I could see it easily without glasses at higher magnification, but the lower magnification view was equally if not more engaging. I also found that fainter stars are readily visible wearing glasses versus my uncorrected vision. Another effect of astigmatism. Oddly, it does not seem to be as much of a factor when observing with a telescope (one eye versus binocular vision), even at lower magnifications. I'm planning side by side comparisons with the TV-101 and the 100XL to explore that more thoroughly.

 

Fiske


Edited by Fiske, 19 September 2021 - 12:30 PM.

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#40 ECP M42

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Posted 19 September 2021 - 07:11 PM

I don't think there is a standard as to where the measurements are taken.   Pat

In fact, there would be various "standards" or standardized "procedures", but since they are never mentioned alongside the measured value, it is always impossible to have a coherent and useful data.

There are formulas that simplify the values and provide data that is only nominal. Then there is the measurement taken from the surface of the glass which, however, does not take into account the possible recess of the ocular lens and there is also the measurement made by the support surface of the eyepieces, but which does not always provide an effective value suitable for everyone the types of glasses (flat or rounded).

 

However, it seemed to me that the values provided by Pinac, are slightly lower than those I personally measured (of some other examples) ... as if his (used) instrument had to be calibrated.


Edited by ECP M42, 19 September 2021 - 07:12 PM.


#41 Jon Isaacs

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Posted 20 September 2021 - 04:34 AM

With telescopes, yes. With binoculars increasing the magnification past some level requires a lot more effort/ingenuity than swapping eyepieces.

 

 

That is really my point.  With binoculars, you are not really working at the optimal magnification for a given aperture.  

 

Your observation about faint stars and astigmatism, it may be due to the fact that it is easier to get sharp focus with a telescope. 

 

Astigmatism so far has not been an issue for me.. Somehow I got lucky in that regard.. My observing eye correction is 0.0, 0.0, and my other eye is 0.25, 0.0.. My glasses is just very expensive bifocals.. 

 

Jon

 

PS: STF 2816 Cepheus looks interesting.. 


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