Are my eyes the weak link?

[maclean]

Hello everyone.

been reading about averted vision and whatnot, as like many others - when viewing faint objects I've found that not looking directly at the object actually produces a sharper image than looking directly at it.

Something which I find frustrating as I naturally prefer looking directly at my targets weather in astronomy or day to day things.

And its this sort of: YAY I can see more, BUT im not 'looking' at it, catch 22 type thing.

But upon reading up about our lack of rod cells (or whatever they are) in the center of our eyes which can deal with dim black and white light - I don't know if im getting confused here, but are our telescopes actually sending colour through the eyepiece, and it is infact our eye that is the weak link here?

Are there some animals out there that have better eyes than us and if they were able to care about the stars, could see colour through an amature telescope? If we could hypothetically create a big enough telescope that could resolve these objects 'brighter' would we be able to see colour at the eyepiece of a hypothetical big enough scope?

Have found myself curious lately about the whole telescope system and the fact that my eye is possibly the crappiest part of the whole system.

I'm wondering if this is what lots of people come to realise and hence buy a camera (something else I am considering lol)

[Stu]

The human eye certainly is not ideal for viewing faint colour objects. The information is there, ir is just there is not enough light to stimulate the colour receptors in our eyes.

One intermediate step which still allows a live image to be viewed is a colour cctv camera such as the Samsung which is quite popular. This generates live colour images by integrating frames over 5 to 10 seconds, and having a very sensitive sensor. It obviously does not produce images of the quality of long exposures, otherwise everyone would use them, but does allow colour to be seen. There is a Video forum on SGL somewhere where there is further info and discussion

Cheers

Stu

[acey]

Our eye is spectacularly well adapted to perform over a huge range of lighting conditions. But looking at galaxies through a telescope is not something we've evolved to do, and is at the limit of our physical ability. That's what makes it interesting.

The most absorbent medium that photons pass through on their way from a star to your brain is your own eye: only a small percentage of photons hitting the surface of the eye actually make it to the retina and initiate a nerve signal (maybe as low as 1% IIRC). As we age the fluid inside the eye becomes even less transparent.

There are many nocturnal creatures that function far better at night than we do: cats have much better night vision, and some animal species can detect infra-red. But our eyes are what we've got and it's pretty amazing what can be done with them. For most observers the real weak link is the light polluted sky.

[xyz]

Averted imagination can also help with seeing colours

[Capricorn]

The human eye isn't evolved for looking at the skies, if it were the the other carnivores would have basically have eaten us before we got this far. We aren't evolved for stationary objects either, we see movement the most, as in something moved there, can I eat it or will it eat me?

Makes you wonder why we do this looking up lark.

I find averted vision allows me to know that whatever faint object I want to see is actually where I am looking. But beyond that really a bit pointless. As in "Yes I am/was looking at the right place just couldn't see anything directly".

I equally recall someone saying that the idea that you couldn't look straight at a dim object and see nothing was incorrect. They said that if you kept looking that eventually the brain puts all the information together and makes something of it. This was in a lecture somewhere and they were very sure of it, think that the person was an imager but they were talking about the action of the eye. Have to say never done it and it goes against every thing normally said, but may be worth investigating, I will when I get the opertunity just to give it a go. Make up your own mind.

[Peter Drew]

Another "weakness" can be experience, the more you train your eye, eventually the more you see.

[jimmyjamjoejoe]

Another "weakness" can be experience, the more you train your eye, eventually the more you see.

True, it's very hard to explain to someone, but you do "learn" to look at things, especially with planetary views.

[maclean]

Thanks for your respnses guys..

I'm now even more curious as I'm getting the impression that not everyone here agrees with the whole averted vision thing....

Is this something that is not agreed on by everyone?

Over some of the last few times I've been out I tried out various things in attempt to resolve as much details as I physically could on the objects I was looking at.

The ring nebula for e.g. (one of my favs atm) just looses soo much detail if I look directly at it. It becomes more of a blur, if I look slightly to the side of it (only a bit) - there is a definate increase in detail but feels uncomfartable and there is just an unbelivable urge to look directly at it.

At first I thought this was due to me eyes being un-adapted, so I got a cover put it over my head and eyepatch on the other eye and sat at the scope for about 20mins just constantly following and looking at the ring nebula. At the end of this 20min following session I was still experiencing a very noticable increase in detail by looking slightly to the side of it.

I had a similar expereince when looking at some globular clusters and for some of th GCs this technique honestly made the difference between a blur and seeing thousands of little points of light... For me.

For the planets I have seen so far (saturn and mars) and moon I can only assume they transmit enough light as this averted vision thing only seems to make a difference on the faintest of objects for me. The fact that I can see colour in them must suggest that they are many many times brighter than the deep objects.

Hey Peter I can understand that, I've only had a scope this summer and difference between my first outing and now is huge. The diffence between now and 2 or 3 years must be big aswell :-)

When you say 'train' yourself though - Do you mean the act of regularly skygazing 'exercises' parts of your eye and makes physical improvments (like going the gym to bulk up)

Or do you mean in a more Phycological kind of way?

[MikeWilson]

The human eye certainly is not ideal for viewing faint colour objects. The information is there, ir is just there is not enough light to stimulate the colour receptors in our eyes.

One intermediate step which still allows a live image to be viewed is a colour cctv camera such as the Samsung which is quite popular. This generates live colour images by integrating frames over 5 to 10 seconds, and having a very sensitive sensor. It obviously does not produce images of the quality of long exposures, otherwise everyone would use them, but does allow colour to be seen. There is a Video forum on SGL somewhere where there is further info and discussion

Cheers

Stu

^ This is a great suggestion. Also a DSLR (any: go for a Canon EOS, ideally) with a cheap intervalometer set to 10 seconds at ISO 1600 would make a good substitute for a video astronomy rig. Works very well on galaxies and nebulae, especially if modified but it's not crucial!

All the best,

Mike

[Marki]

When you say 'train' yourself though - Do you mean the act of regularly skygazing 'exercises' parts of your eye and makes physical improvments (like going the gym to bulk up)

Or do you mean in a more Phycological kind of way?

My own experience after about 9 months (and given the weather until recently, that doesn't add up to a lot of time at the eyepiece really), is that I have learnt to see more, and particularly using higher magnifications (usually giving less bright images for me). I think it may be a combination of physical training and a mental adjustment (isn't all training?). It may be that the pupil dilates more if repeatedly dark-adapted, but also your brain learns to make the most of the limited information it is receiving - maybe your body optimises the nerve links to the eyes and rods in particular. The difficult bit for me is to distinguish between actual improvements in seeing feinter objects/detail from simple imagination (as your brain tries to fill in the gaps by reference to images it "expects" to see - the "eye of farith"). Well that's how it seems to me, at least.

[Stu]

Hi maclean

I don't think there is much dispute about the importance and usefulness of averted vision. Alot depends upon the aperture of the scope and the brightness of the object being viewed.

Some examples, when viewing the globular cluster M13 with my 106mm refractor, averted vision makes a significant difference and many more stars start to resolve. With the 200mm mak, it will take far higher magnification and the whole cluster is visible with direct vision in good conditions. Averted vision still adds more but direct vision gives a very good view still.

The Veil nebula through a 15" dob/OIII filter is visible with direct vision, and looks amazing. Through a 106mm refractor at a dark site the brightest parts are visible but the more delicate parts require averted vision. In binos, the brightest part was only just visible to me with averted vision.

Personally, I rarely see colour in any objects apart from stars. The only exceptions I can think of are the blinking planetary (green), the blue snowball (er, blue ish) and recently Uranus. I guess this is because they are bright enough to stimulate the colour receptors. I don't see colour on Jupiter or M42 for instance. I do know that plenty of people see more colour than me, young eyes in particular are far more sensitive, and pupils dilate more. Everyone is different in what they see, which is why there is such variation in scope choices, and why some people prefer imaging because they want to see far more than is possible with your eyes.

I find averted vision annoying to use at times, but the results are worthwhile to me. The only real way to reduce the requirement is by getting a bigger scope....welcome to aperture fever! :D

Stu

[david9091]

nice post

[maclean]

Many thanks for the various posts on this, I've read them all and found it all valuable stuff cheers all.