Laser collimators

[oldpink]

mine is a snug fit but if your is loose a couple of wraps of electrical tape may help

[wolfpaw]

mine is a snug fit but if your is loose a couple of wraps of electrical tape may help

I tried that and the laser still disagreed with my Cheshire so I ditched it.

[PeterCPC]

I have used a laser that i got off E Bay and it does help but I found that the fit was loose so I added some insulation tape to ensure a tight and central fit. You must make sure though that you have exactly the same thickness of tape all around. I used this and a Cheshire to get accurate collimation and now just check it using the laser. Seems to work ok on my Dob.

Peter

[Charic]

Wolfpaw........I tried some tape, but no joy, too tight. I also noted that just tightening the two focuser lock screws dislodges the alignment ( would be beneficial to have three screws like on a  finder scope  or secondary, to allow laser  tool alignment , now there's another DIY project to add another lock screw just for this purpose?)  I believe a single lock screw that tensions the metal belt inside the holder ensures a snug central fit (similar to the revelation Barlow locking system)

What I actually do, is just apply pressure to the end of the laser, whilst tightening the screws gently. That seems to work for me, but its the awareness that's more important.

So many  folk use the lasers, and unless they are fully collimated and perfectly central, they will differ to  a Cheshire, giving "wrong results" ending up in the bin or just not used, as they become "un-trusted"! 

No matter which method anyone uses, always centrally align the secondary mirror to the focuser tube first.  Then adjust the tilt of the secondary (Using Laser if required) Then finally align the Primary (Barlow the Laser for this part of the collimation ) job done!

If your laser dot still moves around in the primary by some degree, then the laser tool still needs calibrating. If the laser dot moves, ie scribes a circle and stays within the centre spot, I wouldn't worry too much about that, but if it goes out side, the laser tool needs collimating. I've collimated my laser at a distance of about 18 feet and the laser dot stays put during tool rotation in my jig.

I'm not sure how accurate my eye is with a film cap to centralise the secondary, so I'm considering the purchase of a sight tube with cross hair, for this purpose only,  but still working out the formulas for the length of the tube? I think my optics are collimated to the best they can be at present.

It really doesn't matter how far out the laser is when Barlowing the primary mirror for final adjustment, because the Barlow spreads the Laser beam all over the place. This results in a shadow/reflection of the centre spot  which is now visible over the target / Bullseye on the Laser face. Just centralise the ring around the hole. So easy to adjust if your on your own at night.

[mitchelln]

Barlow the laser to collimate the primary. It eliminates any issues with the laser moving due to focuser slop. You can even waggle it and you'll see the reflected donut image on the collimator face does not move