The most critical piece of observing equipment ?

[John]

I'm referring to the human eye, of course

At the International Astronomy Show on Saturday I had a very interesting discussion with John Timmins of Peak 2 Valley Instruments. We discussed the potential optical performance of the various telescope designs with John's favourite being the refractor. John shared some interesting resolution test results obtained in the USA and using US military test charts comparing refractors, SCT's, newtonians and a couple of other designs. 

To round the discussion off John quite rightly raised the issue of the observers visual acuity and how much that varies person to person with a corresponding impact on the perceived performance of the telescopes of course.

Thinking about this since the discussion with John, I've been thinking on how much discussion there is within our hobby comparing x optics to y optics, eyepiece type a with type b and so on. With production quality being pretty good these days the differences between the performance of optical items seem to be getting smaller and smaller and much of the discussion seems to be on examining relatively small differences in light transmission, colour correction, light scatter etc, etc. 

What I'm interested in is how we might realise when we reach a point where the performance differences between manufactured optics fall below the thresholds of variations that are natually to be found within our human optical systems. How can we tell whether differences that we percieve and discuss are products of our own physiology rather than the product of the optical system that is presenting the image to the eye ?

Not an easy question to answer of course, not least perhaps because I suspect many of us do not know a lot about the precise state of our eyes ?. I'm certainly overdue for a test !.

I've no easy answers to this I'm afraid but somebody else might have some useful contributions to make and I'd be interested in hearing them

Can't resist posting this piece of art by Tim and Asia Wetherell

 

[Ben the Ignorant]

58 minutes ago, John said:

How can we tell whether differences that we percieve and discuss are products of our own physiology rather than the product of the optical system that is presenting the image to the eye ?

We can after we accumulate lots of experience and knowledge, but few will get the complete expertise.

[ronin]

One other aspect that is overlooked/ignored or whatever is that there is no reason to suppose that scope A and eyepiece B will be a compatible pairing. They may simply not work well together. When you throw in a barlow then the chances of all 3 being a good operating system together really drops.

I would suspect that TV are about the only ones that have any degree of scope design related to barlow/powermate design related to eyepiece design. Most will produce an item in isolation to the rest of the optics, many have to I suppose and outcomes may be reasonable but not optimal. An eyepiece's performance in a way has to differ on scopes from f/5 to f/10. We just presume that all are equal.

[Paz]

This is an interesting topic. I certainly feel like my scopes are better than my eyes. I thought my first scope had a problem but traced it to my own astigmatism, which I didn't even realise I had.

I watched a video on YouTube recently about vision and although the picture quality is not great you can pretty much just listen to it like a podcast. I can't post the link but it was called...

 

Your eyes - a user's guide to visual astronomy by Dr Myron Wasiuta to the Northern Virginia Astronomy Club.

 

 

[domstar]

1 hour ago, John said:

Not an easy question to answer of course, not least perhaps because I suspect many of us do not know a lot about the precise state of our eyes ?. I'm certainly overdue for a test !.

 

You got Neptune in binoculars last week so yours are probably doing OK.

I'm new to this but have you more experienced observers noticed your views getting better or worse? How can we compare floaters?

[Peter Drew]

I can definitely say that as telescopes have gradually got better, my eyesight has got worse. I can no longer see M33, Alcor or split the main pairing of Epsilon Lyrae naked eye. This is offset somewhat by experience but I am finding I need a larger aperture and more magnification to do as well as I used to. Although I agree that the eye is the most important item in the optical train, seeing conditions probably have the largest impact. 

[Alfian]

Thats an interesting one John. I've been acutely aware of changes in my eyesight this last couple of years, nothing disastrous, but its certainly made me think of being more appreciative of what I can see rather than having some kind of "if only" type of wish list.

12 minutes ago, Paz said:

Your eyes - a user's guide to visual astronomy by Dr Myron Wasiuta to the Northern Virginia Astronomy Club

Looks an interesting item. I assume its this:

 

[scarp15]

Interesting discussion and quite applicable if quirky art piece, concerning the most crucial element in the optical system. I go for an annual eye test, necessary due to family glaucoma, only to conclude that my vision with age, is not as good as the last time. However this should not be a deterrent, for example my daughter could easily out sprint me, yet I would be able to beat her in a half marathon. Concerning visual astronomy, you learn to see and to perceive objects in a particular way, which takes time, patience, dedication to learning and experience, equally you learn how best to utilise and to modify your optical equipment.  To gain the most from my own sense of vision, I like to get to dark sky locations, to become dark adapted, to spend more time becoming accustomed to looking up at the sky than through the eyepiece, to scrutinise and employ visual techniques such as averted vision. Fortunately a lot of what is perceive can be shared and confirmed, such as on the forum in descriptive accounts and in visual formats through dedicated sketches. Of course if my daughter had the interest and patience, what she would be able to visually perceive on a dark sky trip would completely excel what I am now capable of.  

[Paz]

14 minutes ago, Alfian said:

Thats an interesting one John. I've been acutely aware of changes in my eyesight this last couple of years, nothing disastrous, but its certainly made me think of being more appreciative of what I can see rather than having some kind of "if only" type of wish list.

Looks an interesting item. I assume its this:

 

Yes that's the one!

[Charic]

59 minutes ago, Paz said:

I thought my first scope had a problem

ah-ha!........Did you ever own the CP127EQ? .........now there's a problem Lol.

Yes, at the end of the day, only our eyes alone  can resolve the real answer  as to "which is the best eyepiece for me and my scope", it's something that cannot be assumed from reference alone........you need to try for yourself, and everyone's eyes will perceive and detect differently.

If a group of fellow loungers got together and setup what they believed ( after careful consideration ) to be the perfect scope/eyepiece combination, that group would still have visual differences to contend with. 

Secondly, site and conditions? Unless you are already blessed with the perfect site and conditions, finding better will drastically improve what you see through the same scope.

[Floater]

Ask the little ones with young eyes to tell you how many stars they can see in the Pleiades ... and then peer to see if you can catch up! ?

[Paul M]

15 minutes ago, Floater said:

Ask the little ones with young eyes to tell you how many stars they can see in the Pleiades ... and then peer to see if you can catch up! ?

I did exactly that with two young ladies last winter. I pointed them towards the Pleiades without any prompting of what they might see. They both counter well over 7 stars each. Now and for some years they've been a fuzzy blob to my unaided eye

Yet I seem to pick out more and more each time I look a jupiter through my scopes. So I'm still on the upslope of increasing skill outpacing deteriorating eyesight

[Luna-tic]

5 hours ago, John said:

I'm referring to the human eye, of course

To round the discussion off John quite rightly raised the issue of the observers visual acuity and how much that varies person to person with a corresponding impact on the perceived performance of the telescopes of course.

 

 

3 hours ago, Floater said:

Ask the little ones with young eyes to tell you how many stars they can see in the Pleiades ... and then peer to see if you can catch up! ?

It's a great reality check; this past several weeks, each Monday night we've had a Boy Scout Troop at the observatory, to help them with their Astronomy merit badge. When clear enough, we've set up several scopes both to teach how to use them, and to teach about the objects we're looking at. This past Monday was exceptionally clear, and we were looking at star colors, some clusters, and a couple of deep sky objects. I pointed in the general direction of Andromeda and mentioned that if you looked really carefully, you could barely see a "dim fuzzy". Several of the young kids readily saw it and sort of had the attitude, "whattaya mean, dim? I see it fine". I can only see Mizar and Alcor as separates through 3x or better magnification, and Polaris's companion with fairly strong magnification. All the young kids could split Mizar/Alcor naked eye. A couple of the kids could readily detect M13 naked eye. With my advancing presbyopia, I sure can't, even on a perfect night.

[Dave In Vermont]

Carl G. Jung wrote much about human perception and showed it very much involves the human-mind - as well as the physiology of the creature doing the percieving.

The experiment he used to demonstrate this theory was to set two people out on a walk, armed with note-pads and pen/pencil. And they were tasked with noting the things they each saw on a short stretch of the road. And the result showed a wide variation:

#1. noted seeing a bird on a telephone-wire, a car with a cracked windshield, a house with red shutters, so forth.

#2. noted a man using a key to get into a house, a Cat snoozing in the Sun on a porch, a car halfway in & out of a garage, and such.

Identical location. Unmistakable differences in perception.

My 2¢,

Dave

[Piero]

Another thing that affects our sight is alcohol. Pretty obvious of course! What I found less obvious was that even a very small amount (e.g. a small beer) affects the views at the eyepiece, while it seems not to affect at all one's sight normally.

[chiltonstar]

40 minutes ago, Piero said:

Another thing that affects our sight is alcohol. Pretty obvious of course! What I found less obvious was that even a very small amount (e.g. a small beer) affects the views at the eyepiece, while it seems not to affect at all one's sight normally.

Logically, alcohol should improve vision by increasing blood flow to the eye etc, but there is probably a point at which the detrimental effects set in!

We know how our visual acuity decreases with age, eg the above post re the Pleiades, but how about sensitivity to low level light - does that decrease too?

Chris

[Alfian]

I don't know whether varying sensitivity to alcohol affects visual acuity in a direct physiological manner or not (I guess it does) but I've certainly found as I've grown older that I can drink very little alcohol without the more predictable side effects being intolerable, and therefore I choose only to drink little. Having a drink  before an astro' session is not an option, it would be pretty embarrassing being found asleep at the eyepiece!

[Piero]

Maybe it is just my body, but I never found any benefit from alcohol when observing, just disadvantages. I am talking small amounts of alcohol, like drinking one beer at dinner. My sight does not look affected at all, but I can surely notice the difference at the eyepiece. The detection of threshold stars as well as faint planetary details are certainly lost.

For me astronomy is a alcohol-free hobby, which is anyway a good thing! English tea with milk or Ginger soup (as a Chinese friend of mine calls it) are more than sufficient to get warm!

[Macavity]

Anecdotally, a well-known Astronomer takes a hefty "swig" of Oxygen
before observing? But he had quasi-perfect skies and a great location!
BEER helps uz lesser mortals to cope with our situation? [Part joking]   

Beyond the "20:20", some people seem to have exceptional eyesight?
My late Dad was (truly?) "best shot" in his (WWII) "Home Guard" unit!
He could definitely see things I couldn't see... Even when I was a kid.  

I showed the guy who was helping me "Landscape" my garden a view
though my (then) PST. With NO experience of Astronomy he described 
quite *wonderful* things, that I was never able to see through it! lol

I have created / re-vamped a VISUAL setup now. Y'can't beat it tho? 

[RWB]

I keep seeing references to star colours but the only colour I have ever seen through any 'scope was the fabled 

red spot on Jupiter and that really surprised the bejebers  out of me as I am 'shade' blind with red being the colour that

that I have trouble seeing most, so I rather envy you guys (and gals) that can see colours in the stars,

If there is a rainbow I only ever see three or four bands!!

Regards            Robin 

[Stu]

2 hours ago, RWB said:

I keep seeing references to star colours but the only colour I have ever seen through any 'scope was the fabled 

red spot on Jupiter and that really surprised the bejebers  out of me as I am 'shade' blind with red being the colour that

that I have trouble seeing most, so I rather envy you guys (and gals) that can see colours in the stars,

If there is a rainbow I only ever see three or four bands!!

Regards            Robin 

That really surprises Robin, I personally think that my eyes are not particularly sensitive to colour but stars are definitely  some of the clearest that I see.

As a for instance, if you view Betelgeuse and Rigel in Orion when it is well placed, can you definitely not see the colour difference between these?

I have a couple of comments on this topic. Firstly my eyes are very different. By this I mean that my right eye gives bright views, quite colourful but I would describe them as being low resolution, or more like a poorly tuned TV. In the daylight it is perfectly fine but in low light levels this really becomes obvious. My left eye seems slightly less sensitive, but does give me much better defined views of all object types, although I do suffer from annoying floaters which make planetary and solar  observing with small exit pupils less easy. I can comfortably use binoviewers for solar observing but just don't find I see as much detail for planetary observing so stick with cyclops.

Back to topic, I think if my left eye was as bad as my right eye, I would possibly have given up visual observing by now, but at very least would not bother spending a lot on high quality kit. With my left eye of find I do see the improvements generally, although as Peter says, seeing conditions generally play as significant a role in what I get to see.

As a reference, I can quite easily split Alcor and Mizar but not the Epsilon Lyrae pair. I just about see M13 naked eye under a very dark sky.

As others have mentioned I have seen very clearly how much more sensitive young children's eyes are, picking up objects very quickly when I struggle. I just wish I had started the hobby earlier than 30!

Experience does help a lot though. I mentioned earlier that my eyes are not so sensitive to colour, but I definitely see more on, say, Jupiter now than I did when I started observing. Some of that is kit used, my Tak definitely shows me more planetary colour, and also for instance a green caste to M42 than I remember seeing before. It is good that experience can, to a small degree, compensate for degradation of vision as we age.

 

[scarp15]

Becoming comfortable is a particular advantage to visual sensitivity. You have found your target, whether you prefer to sit or stand, intend to analysis and perhaps resolve a specific feature, good posture relaxes the mind, the eye muscles relax, almost transcending into a meditational state, so the image is sharp and accentuated. Not unlike sitting on your favourite chair to read an absorbing novel.

[spaceboy]

I spawned a similar thread a while back John. I have regular eye tests due to glaucoma in the family but the thread actually arose from my concern that a fellow friend and SGL member may have possible eye issues they aren't aware of. It came after they continually questioned the performance of a scope that had already been checked against another and one what many hold in high regards. I think it is all to easy to hold a piece of astronomy equipment as responsible for poor performance and over look the first optic in the train.