poor eyesight, 'where' is the image my eyes focus on -

[Eastridge]

Hi,

I can't seem to see details in planets like hubby can & can seem to get them in sharp focus , I am wondering if the problem is my eyesight. Knowing how far away the actual image I am seeing is from my eyes might help understand this. What I mean is for the purposes of eyes focussing - is the image 'in' the eyepice or 'in' the scope somewhere?

I have been short sighted all my life and astigmatic so correct with glasses. In the last few months I have noted that with my glasses on I can't read small print close up ( anything say within 36 cm / 14") but if I take my glasses off I can read it perfectly. I am getting old!

So, you would imagine that either with glasses on ( if the image I am seeing in the scope is more than 14" away from my eyes) or off (if it's closer than that e.g. 'in' the eyepice) I should be all right but no. Neither work.

Knowing where the image is for the purposes of eye focus might help me work out what the problem is.

Can anyone educate me?

Thanks,

[Pappy Nick]

Hi Eastridge ...

My eyesight is the opposite to yours. I can see clearly for miles, but can't read anything closer than arm's length without glasses.

The strange thing is though is that I can see everything through the eyepiece of my telescope pin-sharp and my eye is only millimetres away from the glass!

I get the same thing with my camera - if I use the viewfinder I can see everything clearly, if I use the lcd screen then I can't see a thing.

Let's hope someone clever will join in and enlighten us

[Neil McRae]

Hi Eastridge

Do you mean you cannot get sharp focus AFTER your husband has focussed the object ? If that is the case you will have to adjust the focus on the scope yourself.

Hope that helps

Neil

[pajr777]

The rays of light passing through a focused lens are collimated - that is they are parallel to each other - much the same as light from an object at infinity. So the object in the ep is effectively at infinity from the eye's .. er .. point of view

If you change the focus of the lens then that counteracts any problems with the eye - you decollimate the light entering the eye and the imperfections in the lens inside the eye recollimate the light hitting the retina. Hence why us spectacle wearers still get sharp focus at the eyepiece without our glasses.

A telescope focussed by someone with good vision will appear unfocussed to someone who is short sighted, and vice versa.

Eastridge, have you tried adjusting the focus yourself or are you relying on your husband's focussing?

[jflowers]

Badly short sighted here too. I wear contacts most of the time, the toric type as also have astigmatism, and glasses the rest of the time. When at the scope, I can get a perfect focus with glasses/contacts and also without anything, but the focus point is slightly different. Try without glasses, you may be surprised

Incidentally, my wife always has to change the focus by quite alot after I have focused on an object perfectly for me.

[Capricorn]

When you adjust the focuser and get something in focus then what you "see" is at the rest point of your eye.

If you are short sighted then this rest point is at a position reasonably close to you, say 12-30 inches.

If you have ideal eyesight then the rest point is infinity.

If you are long sighted then the rest point is somewhere beyond infinity.

By the way what you refer to as the image is actually the object, the image is formed on your retina. They are sort of interchangeable terms. Strictly you are looking at an object, and your eye is forming the image.

[themos]

I find that I don't need an eyepiece at all, especially for the moon!

[Eastridge]

Thanks folks. I do always re-focus myself & not rely on hubby's focussing and I have tried with & without glasses & with my toric contact lenses. The moon is fine it's planets where I seem to be unable to see what he can.

Based on the 'rest point' / infinity information & what others are saying it seems like my eyesight shouldn't be the problem, so I think I will get collumation of the scope re-checked by hubby with the good eyes.