Refractor Collimination.

[Tandum]

I use a meade DS80 as a guide scope. I found that you can use a cheshire eyepiece during the day to check collimination on a refractor. It worked fine on the tak, however this meade is out and it has no alignment screws. I found a manual for it on line and it says alignment is factory set.

Does anyone have any tips on aligning the front cell on a scope with no alignment screws?

[gbeal]

Can you work out which way it needs to "tip/tilt", and by roughly how much?
If so, then is it possible to shim it within the cell?
Gary

[Tandum]

Not easy to shim inside the cell. There are 2 lenses in the front of it. I've had a closer look and it appears the whole front cell is held to the tube with 3 pk screws. I'd say they fit and align the front cell in the factory and then drill the holes for the screws and screw it on. I might try that here and drill new holes :)

[GeoffW1]

Hi,

Could you tell us more about this? I have not done my own research very well.

Is there a reference?

Cheers

[lacad01]

Not sure if applicable here but I've seen other threads where collimation on refractors can be acheived by adjusting the seating of the focusser or unscrewing the focusser captive screws, rotating the focusser and resecuring.

[Tandum]

http://www.spacealberta.com/equipment/refractor/collimate.htm

I picked up on it there Geoff, you see multiple reflections of the cheshires metal angled surface with the hole in the middle showing up as many black dots inside silver circles if it's out. Just adjust to line all the black dots up. I star checked it and it was all good for me. You do it with the lens cap on and the cross hairs in the cheshire are a bit of an obstacle but it does work and it is quick and easy.

[Tandum]

Cheers Adam, I never even thought about the other end. This one has had the R&P focuser changed to a rotatable crayford and there's the problem. Took the front cell off, taped paper over the tube end and shot a laser down the tube. Twas a mile off, like 1/2 way from center to the edge of the tube. Re centered the focuser and it's now a lot closer. Thanks all.