Training the eye

[Ursa Major]

I have heard people saying on the forum that you have to "train your eye" to see details in dso's, planets etc.

I am right eyed myself and have noticed that looking through my binoculars my right eye can focus a lot better than my left eye.

I am 17, so I have quite young eyes.

For my short time (4 months) observing with a telescope (using my right eye) is/can/would it be possible to actually improve just the right eye?

What experiences have you had with the effect of observing on your eyes?

[acey]

I don't think it's the eye itself that improves, but rather the observer's ability to perceive details. Comparison: if you start birdwatching you see there are lots of little brown birds that all look much the same. With practice you know which features to look for, and you begin to distinguish different species.

Similarly with, for example, galaxies. When I started out they all looked like fuzzy blobs. Now when I look at a galaxy I can make a fair guess whether it's a spiral or elliptical. It's still a fuzzy blob, but I know from practice what to look for (things like shape, the way the light decreases from centre to edge, sharpness of edge).

There are objects I can see now that I probably wouldn't have noticed previously. It's not because my eye has improved, but because I know from experience that patience can be rewarded, and I'm prepared to give it longer. I'm also better at finding the right spot to look at.

I would also say that I'm more comfortable about finding my way around in the dark, having done it so often, as I'm better at using the available light.

[Minet]

I've read in New Scientist that what we see is in part a prediction of what the brain expects us to see on the basis of previous experience. The brain has to do this because in order to provide a real-time experience of the world it has to compensate for the delay in processing visual information and the limited amount of the information we recieve from our eyes.

Personally I find it a little disturbing to think that the seamless experience I have of the world is at least in part an informed guess.

In regards to astronomy I have noticed that with very little experience I can see stars with the naked eye which before were invisible to me. I suspect this is largely due to knowing that they are there via the use of star charts and my bins. The stars below Deneb in particular spring to mind because prior to yesterdays observing with my bins I hadn't seen them before and now I can see them with the naked eye.

Similar to the other person I also had similar experience when it came to identifying organisms which initially look very similar but once you know what you are looking for suddenly appear very different.

[JamesC]

Check how you are focusing your binoculars. You might find the ideal focus is slightly different for one eye than the other. Put the cap on the side that doesn't have the eyepiece adjustment and focus the bincoculars. Then swap the cap over and adjust the focus for your other eye using the diopter adjustment on the eyepiece. Then look with both eyes!

I reckon the main things to learn for viewing DSOs is averted vision and trusting your eyes. If you've practiced looking on target and a bit off target and have seen the averted vision effect then you've probably already got the hang of it. Switching between averted and direct vision becomes second nature quite quickly. I like to scan up and down away from my nose so as to avoid the blind spot. With faint features you are looking for subtle changes in the brightness of the night sky. After noting some features on some faint objects and then comparing to photographs I began to realise I really was seeing some faint features and began to trust my eyes more. Some people find telescope tapping, to make the object wobble a bit, helps them pick out faint features. I've certainly found with M31 that moving off target and then scanning back helped me pick out the extremities a bit.

It's also worth getting to know your eyes a bit. Look at a bright star or planet and cover each eye alternately. Does one eye produce a tighter spot than the other? What about in binoculars? For me my right eye produces a tighter spot, although actually I get slightly better acuity in my left eye in sight tests (when my pupils are smaller). I recognise the biggest spike I get from both eyes. These spikes get much smaller as I go to even a 5.6mm exit pupil (my binoculars). The size of these spikes tell me how dilated my pupils are. I've sometimes noticed my pupils shrink and widen a bit over an observing session!

[chiltonstar]

Maybe training helps also for finding the most sensitive part of the retina for averted vision. With practice, I have found that "bottom left" of my right eye field is more sensitive than anywhere else, giving up to 2 mags improvement over "direct vision". Talking to others, I get the impression this is a common experience.

Chris

[acey]

The 2 preceding posts raise a good point. The rods and cones of the retina lie underneath a lot of other stuff (blood vessels, ganglion cells etc), and the pattern of these is unique to the individual. So everyone will have particular parts of the retina that are more or less sensitive, and we learn from experience where these are.