Laser Collimators

Michael, I assumed the secondary was correct, but don't know for sure. after laser collimation the seconary is off to the left as viewed thru cap

I don't know. If I removed the secondary to mark it (if thats what you mean) it would be an operation with more complexity than the moon landing :shock:

If I do nothing will it seriously effect viewing? i.e. comprimise between the two?

declan

Never assume anything in collimation!

When collimating from scratch you first need to collimate the focuser (with the secondary mirror removed.) This is best done with a long-barrel cross-hair sight tube but can be done with a laser *if* you can make the laser spot *very* small. Rack the focuser all the way in and mark the opposite side of the tube inside where the spot or cross-hairs indicate. Now rack the focuser all the way out and repeat the process. If the two marks are not exactly on top of eachother then you need to adjust the focuser mounting screws with shims until the two spots line up.

Now you can replace the secondary mirror (and to make things less confusing, remove the primary mirror and its cell so that you can see daylight!) For a 10" f/5 or 6 scope you can effectively ignore the offset as it will probably be less than 1mm away from the focuser and down the tube.

Collimate the secondary (again, best done with a long barrel cross-hair sight tube, but can be done with a laser and annular reticle): Make sure the secondary is correctly positioned along the main optical axis (up and down the telescope tube) and is correctly rotated. Now adjust the three screws on the back of the secondary so that the primary mirror (or the bottom end of the tube if you have removed the primary) is centred in the secondary mirror. When that's done, lock everything in place.

Collimate the primary (don't forget to put it back in the tube first!): Use the three main mirror adjusting screws to centre the centre spot on the primary mirror (use a paper hole-punch reinforcer) is centred in the secondary.

Super-critical collimation is best done with an Auto-Collimating eyepiece.

Phil.

I think I should buy another telescope.......or get someone to help me

thanks phil.....im utterly depressed now

declan

Declan,

Next time your pasisng Monasterevin, bring the scope and we'll go through collimation. This issue wrecked my little head when building my dob but I *think* I understand it now.

Regards,

Thanks I will take you up on that offer, I am a monkey see, monkey do sort of fellow

This sort of locks in with my other thread about Dob tweaks.
What i do now is use a Cheshire, and get everything centred as best I can.
When that's done, I use the laser, and I've found it's normally just very slightly out, so I finish the process with a tweak using the laser collimator...it has made a noticeable difference.
Last time I was getting razor sharp views of Saturn when the atmosphere allowed, and beautiful spiral detail in M51.

Just recieved my Howie Glatter Holographic laser and Blug(barlow target) this moring. Will post a report in this thread in the next day or two with my findings.