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Thread: Help collimating my reflector using a laser collimating device

  1. #11
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    Default Re: Help collimating my reflector using a laser collimating device



    Spork, there are many different ways to build a cradle to hold the laser collimator. A simple V-block built from scraps of wood as shown in the attached photos is an easy alternative.

    Please check that the body of your laser collimator is uniformly cylindrical such that when it rotates in whatever cradle you use, its longitudinal axis (i.e. the laser beam) is stationary. It will not help you at all if your laser is fat at one end and skinny at the other. Not all laser collimators lend themselves to testing in this fashion.
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    Default Re: Help collimating my reflector using a laser collimating device

    It's quite common for the laser dot to move out of the target hole while tightening down the primary mirror lock down screws---The trick is to only tighten the screw until the dot just comes off target and then adjust the next screw in line and then the 3rd screw---You'll end up making minor tightening adjustments in a circular pattern,never letting the dot move too far out of the hole---I'll usually end up going through this pattern 3 or 4 times working around before I actually get the screws snug enough to hold the mirror------You should never have to bare down on the screws--------

    As an example--Take your screwdriver and hold it by only your thumb and first 2 fingers and don't let the handle touch the palm of your hand or just take the screwdriver and smash the handle off,until nothing is left but the smooth shaft--In that configuration you can break a sweat using it and still not over tighten anything--Allot of scopes just have small knurled finger screws,because that's all that is really needed--Snug not tight--Putting Allen and/or star bit screws for adjustment is just a way for the manufacture to save money--Not near the torque is needed that these fasteners are capable of producing--And the only reason there is 2 different ones is so that you can differentiate between the adjustment and the lock down screws --------------------------------------ZX
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    Default Re: Help collimating my reflector using a laser collimating device

    Quote Originally Posted by Spork Schivago View Post
    So for the primary mirror, I can just loosen the really tight one and then tighten the one on the opposite side or the one on the bottom, but not both of those? And some how it'll keep the laser dot right where it needs to be? I'll try building the device tomorrow. My dad has some PVC pipe that I could use.
    You should have three screws for adjusting the primary mirror (forms a triangle). Loosen the one that's cranked down so it's not so tight and use the other two that remain to get the mirror back in pollination. You'll have to use both of the other two to get the mirror back in pollination.

    Think of it like a tripod. If a tripod is not level in the direction of one leg, you can either extend the one leg, or shorten the other two. If one leg is extended all the way and it's still not level, you can't just pull it out more even if you only need that one leg a little bit higher because the tripod will come apart. You have to adjust the other two legs to get it to level. You'd have to shorten the other two. Shortening them both the same amount should bring the whole tripod to level. In a similar fashion, the mirror is attached to your telescope at three points. If you can't adjust the one screw because it can't go any farther (and all you needed was just a bit more), you have to adjust the other two by a fairly equal amount .
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    Default Re: Help collimating my reflector using a laser collimating device

    If you have a Barlow, I recommend the Barlowed laser method for collimating the primary mirror. It's very easy and focuser play doesn't affect the collimation.

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    Default Re: Help collimating my reflector using a laser collimating device

    It was hard to verify the collimator was collimated. However, I think we've successfully verified it was collimated. There's a very small section on the collimator that is round enough. It's maybe an inch, inch and a half wide. We used my wife's Cross Stitch Holder. We were able to put the collimator in it, and screw it down and turn it. I wanted to thank everyone for their generous help.
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    Default Re: Help collimating my reflector using a laser collimating device

    Very useful post. I likewise bought the Twin Star 6" wrongly believing it was a Newtonian Telescope. Had never heard of Bird Jones before. Your post is also comforting.

 

 
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