Expert: Paul Wagner - 3/10/2004

Question
Hi.
I have a Helios Startravel 150mm refractor scope on an EQ5 mount. Part of the kit that came with the scope is an eyepiece which has a pinhole in it, no lens and an aperture at the side with a surface at 45 deg to the light travel path. I believe this may be for columnation of the scope but there were no instructions with the scope which explained how to use it. The scope has 3 adjusting screws on the front element which again I assume are for columnation.

If required, I can send you a picture of the eyepiece.

Could you explain how this eyepiece should be used? Thanks.

Ralph.

Answer
Dear Ralph;

I think I will need a picture to really help you with this one.  A refractor should almost never need collimation, and if it does, that is best done by a professional.  I can't imagine that this is for collimation.

I was thinking it might actually be part of a star diagonal, so that you could use the scope close to the zenith without breaking your neck.  Is that possible?  Does it look like this piece might be missing a mirror or prism?

Paul Wagner