How do you collimate a refractor?

[VinSnr]

Guys...

Just curious.....how many of you has ever collimate a refractor and what are your ways of doing it?

[weixing]

Hi,
I think not many people in SingAstro collimated a refractor before... hmm... may be liu ming (denebman) does it before since he DIY a few refractors.

I also wonder how to do it?? May be I'll try out the method given by this website: http://www.spacealberta.com/equipment/collimate.htm and use star test to confirm.

By the way, I hope I don't need to collinate my new scope once it arrive.

Have a nice day.

[VinSnr]

Hi,
I think not many people in SingAstro collimated a refractor before... hmm... may be liu ming (denebman) does it before since he DIY a few refractors.

I also wonder how to do it?? May be I'll try out the method given by this website: http://www.spacealberta.com/equipment/collimate.htm and use star test to confirm.

By the way, I hope I don't need to collinate my new scope once it arrive.

Have a nice day.

One of the easiest way I have tried is to use a flat vertical mirror. You need two items. One is the cheshire eyepiece with a cross hair (known to be the collimation eyepiece sold by Orion). The 2nd item you need is a vertical flat mirror. Most houses have this. You might have one leaning against your wall in your room. If you do not have one, just go to ikea and buy one peice of the 12" x 12" square mirror and stick it on your wall. (use a level rule to make sure your wall is perfectly vertical....if not, you better call the HDB)

Once you have this, mount your refractor on a mount in a horizontal position. Push it to the flat vertical mirror. The flat mirror should be perpendicular with your dew shield and the dew shield should be touching the mirror. There should be no gap between the dewshield and the mirror. If the vertical mirror is perfectly vertical, your scope should now be perfectly horizontal.

Now place the cheshire eyepiece into the focuser. Position the cheshire in such a way that the 45 degree opening is facing your ceiling. If your ceiling has light shining down the opening, then you are all set. If not, you will have to hold a torchlight shining into that opening.

Now, peep into the hole of the cheshire. You should see the crosshair and the bullseye of the cheshire intersect with one another. If it does not, then you either have to shim your focuser or adjust the lens cell (if it has adjustment screws) until the cross hair and the bullseye intersect with one another. Once this is done, verify it with a star test. When I received the previous Orion 80ED, the collimation was out and I have to shim the focuser using this method. A check under the stars showed that the collimation is right on.

I think you can also try it without the flat mirror, but the reflection of the cheshire will not be so obvious.