eyeball to eyecup

[oldnut]

evening all, I was out with the scope yesterday and as usual I kept getting a masking effect across the eyepiece. doesn't matter which eyepiece I use I get black edges to my vision. out of curiosity I brought my dads old binos home today and have just been out with them, same thing. I noticed that it has to do with when I put my eyes on the eyecaps. if I hold the binos away from my face I loose the masking, tried it with the scope and it was the same, I had been thinking something was wrong with the scope. does anyone else have this problem? can I get eyepieces that would work with my weird eyes?

[Moonshane]

this sounds like you are either too close or too far away from the eyepiece. every eyepiece has what is called eye relief. this is how far away from the lens your eye needs to be to see the whole field.  too close or too far away and you get blackout with some designs. experiment to find the best spot. you can do this with the eyepiece out of the scope. just get your eye to the position where you can see the whole field to the field stop (black circle). this is where you want to place your eye.

[oldnut]

thanks, sorry been on hols in the stix near Weymouth, much darker skies than my way!. i was hoping to find out if its possible to get different length eye pieces so that i don't have to hover away from the eye piece but find a cup the right length.  has anyone home modded eye cups? 

[LukeSkywatcher]

I know the problem you speak of. As Moonshane said, its all about eye relief. Look for eye pieces that have a rubber "twist up/twist down" rubber cap.