[5ash (Philip)]

I have tried collimating my telescope , a fast 8" Newtonian with a Cheshire eyepiece and find it fairly easy and accurate. However I find the cross hair at the end of the cheshires tube difficult to focus on and to obscure my view of the mirrors centre spot. This could be overcome to some extent if the crosshairs had a circular centre that you could look through.To try to solve the problem I took an old eyepiece , removed the lens and replaced the retaining ring to leave a small opening. This gave me a similar tool to a film canister collimator. I then painted the area inside the eyepiece around the hole and its supporting structures with luminous paint as shown by the first 3 pictures . This when exposed to a strong light provided a glowing cross with a centre circle and black dot ,see 3rd picture. When placed in the eyepiece the glowing cross and primary centre spot can be seen reflected in the mirror , see the 4th picture where the primary is just out of collimation. When the primary is adjusted the centre spot can be made to coincide with the centre of the glowing cross to achieve collimation , see the 5th picture. I have used this to collimate the primary mirror and get exactly the same result as with a conventional long tube cheshire , except its much easier to see collimation with my luminous tool. You can also check collimation in the dark after charging the luminous paint with a flashlight.


regards philip

ps The last 2 pictures were taken through the peephole