I have a short Cheshire / sight tube, and would like to pass it onto someone who needs a simple but effective tool for collimating their Newtonian (incl. Dobsonian).
I'm asking for $15 including postage. Or if you're in Melbourne, you're welcome to pick it up for $10.
See attached pictures of the collimating tool. I got it from Andrews for $29 + postage.
More info for those who care to read on:
I had two things to pick on with the Andrews tool after I got it:
1. The cross hairs are thin wires and easily movable/bendable, so I wasn't sure if the X did indeed mark the spot in the centre. But after experimenting with it (rotating in focuser and checking where X moved) I confirmed that the X-hairs are the centre of the focuser, so that is not a problem. But the fragility of the thin wires remains.
2. The tube is very short so you cannot see the X-hairs in focus. Not as big a deal as some seem to think. The way to use the X-hairs is with a bright torch shining down into the opening on the side at the 45degree polished Al surface. This will show the copper coloured X-hairs distinctly; a bit blurred, but the intersection clearly seen as a square. Then you can just centre everything in the square.
Because I'm still not 100% happy with the performance of my scope, I bought the Celestron collimating EP / Cheshire recently for over double the price of the Andrews tool. The Celestron unit is more than twice as long as the Andrews one, so the X-hairs are seen clearly. They are not made of wires but little steel rods. This means they are stronger, but they are also more of an obstruction and lack the precision of X-hairs made from thin wire.
I checked the collimation of my Dob with the Celestron tool and it looks spot on. I rechecked with the Andrews tool and it looks just as good. So in the end both tools do the job, and I'm not sure which one I'd prefer was it not for the cost of purchase. (I'd like a hybrid: thin X-hairs on the end of a long sight-tube.)
I hope this will help out someone on a tight budget.
